| //===- InstructionCombining.cpp - Combine multiple instructions -----------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // InstructionCombining - Combine instructions to form fewer, simple |
| // instructions. This pass does not modify the CFG. This pass is where |
| // algebraic simplification happens. |
| // |
| // This pass combines things like: |
| // %Y = add i32 %X, 1 |
| // %Z = add i32 %Y, 1 |
| // into: |
| // %Z = add i32 %X, 2 |
| // |
| // This is a simple worklist driven algorithm. |
| // |
| // This pass guarantees that the following canonicalizations are performed on |
| // the program: |
| // 1. If a binary operator has a constant operand, it is moved to the RHS |
| // 2. Bitwise operators with constant operands are always grouped so that |
| // shifts are performed first, then or's, then and's, then xor's. |
| // 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible |
| // 4. All cmp instructions on boolean values are replaced with logical ops |
| // 5. add X, X is represented as (X*2) => (X << 1) |
| // 6. Multiplies with a power-of-two constant argument are transformed into |
| // shifts. |
| // ... etc. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "instcombine" |
| #include "llvm/Transforms/Scalar.h" |
| #include "InstCombine.h" |
| #include "llvm-c/Initialization.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/StringSwitch.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/DataLayout.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/PatternMatch.h" |
| #include "llvm/Support/ValueHandle.h" |
| #include "llvm/Target/TargetLibraryInfo.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include <algorithm> |
| #include <climits> |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| STATISTIC(NumCombined , "Number of insts combined"); |
| STATISTIC(NumConstProp, "Number of constant folds"); |
| STATISTIC(NumDeadInst , "Number of dead inst eliminated"); |
| STATISTIC(NumSunkInst , "Number of instructions sunk"); |
| STATISTIC(NumExpand, "Number of expansions"); |
| STATISTIC(NumFactor , "Number of factorizations"); |
| STATISTIC(NumReassoc , "Number of reassociations"); |
| |
| static cl::opt<bool> UnsafeFPShrink("enable-double-float-shrink", cl::Hidden, |
| cl::init(false), |
| cl::desc("Enable unsafe double to float " |
| "shrinking for math lib calls")); |
| |
| // Initialization Routines |
| void llvm::initializeInstCombine(PassRegistry &Registry) { |
| initializeInstCombinerPass(Registry); |
| } |
| |
| void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { |
| initializeInstCombine(*unwrap(R)); |
| } |
| |
| char InstCombiner::ID = 0; |
| INITIALIZE_PASS_BEGIN(InstCombiner, "instcombine", |
| "Combine redundant instructions", false, false) |
| INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) |
| INITIALIZE_PASS_END(InstCombiner, "instcombine", |
| "Combine redundant instructions", false, false) |
| |
| void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesCFG(); |
| AU.addRequired<TargetLibraryInfo>(); |
| } |
| |
| |
| Value *InstCombiner::EmitGEPOffset(User *GEP) { |
| return llvm::EmitGEPOffset(Builder, *getDataLayout(), GEP); |
| } |
| |
| /// ShouldChangeType - Return true if it is desirable to convert a computation |
| /// from 'From' to 'To'. We don't want to convert from a legal to an illegal |
| /// type for example, or from a smaller to a larger illegal type. |
| bool InstCombiner::ShouldChangeType(Type *From, Type *To) const { |
| assert(From->isIntegerTy() && To->isIntegerTy()); |
| |
| // If we don't have TD, we don't know if the source/dest are legal. |
| if (!TD) return false; |
| |
| unsigned FromWidth = From->getPrimitiveSizeInBits(); |
| unsigned ToWidth = To->getPrimitiveSizeInBits(); |
| bool FromLegal = TD->isLegalInteger(FromWidth); |
| bool ToLegal = TD->isLegalInteger(ToWidth); |
| |
| // If this is a legal integer from type, and the result would be an illegal |
| // type, don't do the transformation. |
| if (FromLegal && !ToLegal) |
| return false; |
| |
| // Otherwise, if both are illegal, do not increase the size of the result. We |
| // do allow things like i160 -> i64, but not i64 -> i160. |
| if (!FromLegal && !ToLegal && ToWidth > FromWidth) |
| return false; |
| |
| return true; |
| } |
| |
| // Return true, if No Signed Wrap should be maintained for I. |
| // The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C", |
| // where both B and C should be ConstantInts, results in a constant that does |
| // not overflow. This function only handles the Add and Sub opcodes. For |
| // all other opcodes, the function conservatively returns false. |
| static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) { |
| OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I); |
| if (!OBO || !OBO->hasNoSignedWrap()) { |
| return false; |
| } |
| |
| // We reason about Add and Sub Only. |
| Instruction::BinaryOps Opcode = I.getOpcode(); |
| if (Opcode != Instruction::Add && |
| Opcode != Instruction::Sub) { |
| return false; |
| } |
| |
| ConstantInt *CB = dyn_cast<ConstantInt>(B); |
| ConstantInt *CC = dyn_cast<ConstantInt>(C); |
| |
| if (!CB || !CC) { |
| return false; |
| } |
| |
| const APInt &BVal = CB->getValue(); |
| const APInt &CVal = CC->getValue(); |
| bool Overflow = false; |
| |
| if (Opcode == Instruction::Add) { |
| BVal.sadd_ov(CVal, Overflow); |
| } else { |
| BVal.ssub_ov(CVal, Overflow); |
| } |
| |
| return !Overflow; |
| } |
| |
| /// SimplifyAssociativeOrCommutative - This performs a few simplifications for |
| /// operators which are associative or commutative: |
| // |
| // Commutative operators: |
| // |
| // 1. Order operands such that they are listed from right (least complex) to |
| // left (most complex). This puts constants before unary operators before |
| // binary operators. |
| // |
| // Associative operators: |
| // |
| // 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. |
| // 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. |
| // |
| // Associative and commutative operators: |
| // |
| // 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. |
| // 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. |
| // 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" |
| // if C1 and C2 are constants. |
| // |
| bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) { |
| Instruction::BinaryOps Opcode = I.getOpcode(); |
| bool Changed = false; |
| |
| do { |
| // Order operands such that they are listed from right (least complex) to |
| // left (most complex). This puts constants before unary operators before |
| // binary operators. |
| if (I.isCommutative() && getComplexity(I.getOperand(0)) < |
| getComplexity(I.getOperand(1))) |
| Changed = !I.swapOperands(); |
| |
| BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0)); |
| BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)); |
| |
| if (I.isAssociative()) { |
| // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. |
| if (Op0 && Op0->getOpcode() == Opcode) { |
| Value *A = Op0->getOperand(0); |
| Value *B = Op0->getOperand(1); |
| Value *C = I.getOperand(1); |
| |
| // Does "B op C" simplify? |
| if (Value *V = SimplifyBinOp(Opcode, B, C, TD)) { |
| // It simplifies to V. Form "A op V". |
| I.setOperand(0, A); |
| I.setOperand(1, V); |
| // Conservatively clear the optional flags, since they may not be |
| // preserved by the reassociation. |
| if (MaintainNoSignedWrap(I, B, C) && |
| (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) { |
| // Note: this is only valid because SimplifyBinOp doesn't look at |
| // the operands to Op0. |
| I.clearSubclassOptionalData(); |
| I.setHasNoSignedWrap(true); |
| } else { |
| I.clearSubclassOptionalData(); |
| } |
| |
| Changed = true; |
| ++NumReassoc; |
| continue; |
| } |
| } |
| |
| // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. |
| if (Op1 && Op1->getOpcode() == Opcode) { |
| Value *A = I.getOperand(0); |
| Value *B = Op1->getOperand(0); |
| Value *C = Op1->getOperand(1); |
| |
| // Does "A op B" simplify? |
| if (Value *V = SimplifyBinOp(Opcode, A, B, TD)) { |
| // It simplifies to V. Form "V op C". |
| I.setOperand(0, V); |
| I.setOperand(1, C); |
| // Conservatively clear the optional flags, since they may not be |
| // preserved by the reassociation. |
| I.clearSubclassOptionalData(); |
| Changed = true; |
| ++NumReassoc; |
| continue; |
| } |
| } |
| } |
| |
| if (I.isAssociative() && I.isCommutative()) { |
| // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. |
| if (Op0 && Op0->getOpcode() == Opcode) { |
| Value *A = Op0->getOperand(0); |
| Value *B = Op0->getOperand(1); |
| Value *C = I.getOperand(1); |
| |
| // Does "C op A" simplify? |
| if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { |
| // It simplifies to V. Form "V op B". |
| I.setOperand(0, V); |
| I.setOperand(1, B); |
| // Conservatively clear the optional flags, since they may not be |
| // preserved by the reassociation. |
| I.clearSubclassOptionalData(); |
| Changed = true; |
| ++NumReassoc; |
| continue; |
| } |
| } |
| |
| // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. |
| if (Op1 && Op1->getOpcode() == Opcode) { |
| Value *A = I.getOperand(0); |
| Value *B = Op1->getOperand(0); |
| Value *C = Op1->getOperand(1); |
| |
| // Does "C op A" simplify? |
| if (Value *V = SimplifyBinOp(Opcode, C, A, TD)) { |
| // It simplifies to V. Form "B op V". |
| I.setOperand(0, B); |
| I.setOperand(1, V); |
| // Conservatively clear the optional flags, since they may not be |
| // preserved by the reassociation. |
| I.clearSubclassOptionalData(); |
| Changed = true; |
| ++NumReassoc; |
| continue; |
| } |
| } |
| |
| // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" |
| // if C1 and C2 are constants. |
| if (Op0 && Op1 && |
| Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode && |
| isa<Constant>(Op0->getOperand(1)) && |
| isa<Constant>(Op1->getOperand(1)) && |
| Op0->hasOneUse() && Op1->hasOneUse()) { |
| Value *A = Op0->getOperand(0); |
| Constant *C1 = cast<Constant>(Op0->getOperand(1)); |
| Value *B = Op1->getOperand(0); |
| Constant *C2 = cast<Constant>(Op1->getOperand(1)); |
| |
| Constant *Folded = ConstantExpr::get(Opcode, C1, C2); |
| BinaryOperator *New = BinaryOperator::Create(Opcode, A, B); |
| InsertNewInstWith(New, I); |
| New->takeName(Op1); |
| I.setOperand(0, New); |
| I.setOperand(1, Folded); |
| // Conservatively clear the optional flags, since they may not be |
| // preserved by the reassociation. |
| I.clearSubclassOptionalData(); |
| |
| Changed = true; |
| continue; |
| } |
| } |
| |
| // No further simplifications. |
| return Changed; |
| } while (1); |
| } |
| |
| /// LeftDistributesOverRight - Whether "X LOp (Y ROp Z)" is always equal to |
| /// "(X LOp Y) ROp (X LOp Z)". |
| static bool LeftDistributesOverRight(Instruction::BinaryOps LOp, |
| Instruction::BinaryOps ROp) { |
| switch (LOp) { |
| default: |
| return false; |
| |
| case Instruction::And: |
| // And distributes over Or and Xor. |
| switch (ROp) { |
| default: |
| return false; |
| case Instruction::Or: |
| case Instruction::Xor: |
| return true; |
| } |
| |
| case Instruction::Mul: |
| // Multiplication distributes over addition and subtraction. |
| switch (ROp) { |
| default: |
| return false; |
| case Instruction::Add: |
| case Instruction::Sub: |
| return true; |
| } |
| |
| case Instruction::Or: |
| // Or distributes over And. |
| switch (ROp) { |
| default: |
| return false; |
| case Instruction::And: |
| return true; |
| } |
| } |
| } |
| |
| /// RightDistributesOverLeft - Whether "(X LOp Y) ROp Z" is always equal to |
| /// "(X ROp Z) LOp (Y ROp Z)". |
| static bool RightDistributesOverLeft(Instruction::BinaryOps LOp, |
| Instruction::BinaryOps ROp) { |
| if (Instruction::isCommutative(ROp)) |
| return LeftDistributesOverRight(ROp, LOp); |
| // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z", |
| // but this requires knowing that the addition does not overflow and other |
| // such subtleties. |
| return false; |
| } |
| |
| /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations |
| /// which some other binary operation distributes over either by factorizing |
| /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this |
| /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is |
| /// a win). Returns the simplified value, or null if it didn't simplify. |
| Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) { |
| Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); |
| BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); |
| BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); |
| Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); // op |
| |
| // Factorization. |
| if (Op0 && Op1 && Op0->getOpcode() == Op1->getOpcode()) { |
| // The instruction has the form "(A op' B) op (C op' D)". Try to factorize |
| // a common term. |
| Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); |
| Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); |
| Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' |
| |
| // Does "X op' Y" always equal "Y op' X"? |
| bool InnerCommutative = Instruction::isCommutative(InnerOpcode); |
| |
| // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"? |
| if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode)) |
| // Does the instruction have the form "(A op' B) op (A op' D)" or, in the |
| // commutative case, "(A op' B) op (C op' A)"? |
| if (A == C || (InnerCommutative && A == D)) { |
| if (A != C) |
| std::swap(C, D); |
| // Consider forming "A op' (B op D)". |
| // If "B op D" simplifies then it can be formed with no cost. |
| Value *V = SimplifyBinOp(TopLevelOpcode, B, D, TD); |
| // If "B op D" doesn't simplify then only go on if both of the existing |
| // operations "A op' B" and "C op' D" will be zapped as no longer used. |
| if (!V && Op0->hasOneUse() && Op1->hasOneUse()) |
| V = Builder->CreateBinOp(TopLevelOpcode, B, D, Op1->getName()); |
| if (V) { |
| ++NumFactor; |
| V = Builder->CreateBinOp(InnerOpcode, A, V); |
| V->takeName(&I); |
| return V; |
| } |
| } |
| |
| // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? |
| if (RightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) |
| // Does the instruction have the form "(A op' B) op (C op' B)" or, in the |
| // commutative case, "(A op' B) op (B op' D)"? |
| if (B == D || (InnerCommutative && B == C)) { |
| if (B != D) |
| std::swap(C, D); |
| // Consider forming "(A op C) op' B". |
| // If "A op C" simplifies then it can be formed with no cost. |
| Value *V = SimplifyBinOp(TopLevelOpcode, A, C, TD); |
| // If "A op C" doesn't simplify then only go on if both of the existing |
| // operations "A op' B" and "C op' D" will be zapped as no longer used. |
| if (!V && Op0->hasOneUse() && Op1->hasOneUse()) |
| V = Builder->CreateBinOp(TopLevelOpcode, A, C, Op0->getName()); |
| if (V) { |
| ++NumFactor; |
| V = Builder->CreateBinOp(InnerOpcode, V, B); |
| V->takeName(&I); |
| return V; |
| } |
| } |
| } |
| |
| // Expansion. |
| if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) { |
| // The instruction has the form "(A op' B) op C". See if expanding it out |
| // to "(A op C) op' (B op C)" results in simplifications. |
| Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; |
| Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' |
| |
| // Do "A op C" and "B op C" both simplify? |
| if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, TD)) |
| if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, TD)) { |
| // They do! Return "L op' R". |
| ++NumExpand; |
| // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. |
| if ((L == A && R == B) || |
| (Instruction::isCommutative(InnerOpcode) && L == B && R == A)) |
| return Op0; |
| // Otherwise return "L op' R" if it simplifies. |
| if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) |
| return V; |
| // Otherwise, create a new instruction. |
| C = Builder->CreateBinOp(InnerOpcode, L, R); |
| C->takeName(&I); |
| return C; |
| } |
| } |
| |
| if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) { |
| // The instruction has the form "A op (B op' C)". See if expanding it out |
| // to "(A op B) op' (A op C)" results in simplifications. |
| Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); |
| Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op' |
| |
| // Do "A op B" and "A op C" both simplify? |
| if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, TD)) |
| if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, TD)) { |
| // They do! Return "L op' R". |
| ++NumExpand; |
| // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. |
| if ((L == B && R == C) || |
| (Instruction::isCommutative(InnerOpcode) && L == C && R == B)) |
| return Op1; |
| // Otherwise return "L op' R" if it simplifies. |
| if (Value *V = SimplifyBinOp(InnerOpcode, L, R, TD)) |
| return V; |
| // Otherwise, create a new instruction. |
| A = Builder->CreateBinOp(InnerOpcode, L, R); |
| A->takeName(&I); |
| return A; |
| } |
| } |
| |
| return 0; |
| } |
| |
| // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction |
| // if the LHS is a constant zero (which is the 'negate' form). |
| // |
| Value *InstCombiner::dyn_castNegVal(Value *V) const { |
| if (BinaryOperator::isNeg(V)) |
| return BinaryOperator::getNegArgument(V); |
| |
| // Constants can be considered to be negated values if they can be folded. |
| if (ConstantInt *C = dyn_cast<ConstantInt>(V)) |
| return ConstantExpr::getNeg(C); |
| |
| if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) |
| if (C->getType()->getElementType()->isIntegerTy()) |
| return ConstantExpr::getNeg(C); |
| |
| return 0; |
| } |
| |
| // dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the |
| // instruction if the LHS is a constant negative zero (which is the 'negate' |
| // form). |
| // |
| Value *InstCombiner::dyn_castFNegVal(Value *V) const { |
| if (BinaryOperator::isFNeg(V)) |
| return BinaryOperator::getFNegArgument(V); |
| |
| // Constants can be considered to be negated values if they can be folded. |
| if (ConstantFP *C = dyn_cast<ConstantFP>(V)) |
| return ConstantExpr::getFNeg(C); |
| |
| if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) |
| if (C->getType()->getElementType()->isFloatingPointTy()) |
| return ConstantExpr::getFNeg(C); |
| |
| return 0; |
| } |
| |
| static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO, |
| InstCombiner *IC) { |
| if (CastInst *CI = dyn_cast<CastInst>(&I)) { |
| return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType()); |
| } |
| |
| // Figure out if the constant is the left or the right argument. |
| bool ConstIsRHS = isa<Constant>(I.getOperand(1)); |
| Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS)); |
| |
| if (Constant *SOC = dyn_cast<Constant>(SO)) { |
| if (ConstIsRHS) |
| return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand); |
| return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC); |
| } |
| |
| Value *Op0 = SO, *Op1 = ConstOperand; |
| if (!ConstIsRHS) |
| std::swap(Op0, Op1); |
| |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) |
| return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1, |
| SO->getName()+".op"); |
| if (ICmpInst *CI = dyn_cast<ICmpInst>(&I)) |
| return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, |
| SO->getName()+".cmp"); |
| if (FCmpInst *CI = dyn_cast<FCmpInst>(&I)) |
| return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, |
| SO->getName()+".cmp"); |
| llvm_unreachable("Unknown binary instruction type!"); |
| } |
| |
| // FoldOpIntoSelect - Given an instruction with a select as one operand and a |
| // constant as the other operand, try to fold the binary operator into the |
| // select arguments. This also works for Cast instructions, which obviously do |
| // not have a second operand. |
| Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) { |
| // Don't modify shared select instructions |
| if (!SI->hasOneUse()) return 0; |
| Value *TV = SI->getOperand(1); |
| Value *FV = SI->getOperand(2); |
| |
| if (isa<Constant>(TV) || isa<Constant>(FV)) { |
| // Bool selects with constant operands can be folded to logical ops. |
| if (SI->getType()->isIntegerTy(1)) return 0; |
| |
| // If it's a bitcast involving vectors, make sure it has the same number of |
| // elements on both sides. |
| if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) { |
| VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); |
| VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); |
| |
| // Verify that either both or neither are vectors. |
| if ((SrcTy == NULL) != (DestTy == NULL)) return 0; |
| // If vectors, verify that they have the same number of elements. |
| if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) |
| return 0; |
| } |
| |
| Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this); |
| Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this); |
| |
| return SelectInst::Create(SI->getCondition(), |
| SelectTrueVal, SelectFalseVal); |
| } |
| return 0; |
| } |
| |
| |
| /// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which |
| /// has a PHI node as operand #0, see if we can fold the instruction into the |
| /// PHI (which is only possible if all operands to the PHI are constants). |
| /// |
| Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { |
| PHINode *PN = cast<PHINode>(I.getOperand(0)); |
| unsigned NumPHIValues = PN->getNumIncomingValues(); |
| if (NumPHIValues == 0) |
| return 0; |
| |
| // We normally only transform phis with a single use. However, if a PHI has |
| // multiple uses and they are all the same operation, we can fold *all* of the |
| // uses into the PHI. |
| if (!PN->hasOneUse()) { |
| // Walk the use list for the instruction, comparing them to I. |
| for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); |
| UI != E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| if (User != &I && !I.isIdenticalTo(User)) |
| return 0; |
| } |
| // Otherwise, we can replace *all* users with the new PHI we form. |
| } |
| |
| // Check to see if all of the operands of the PHI are simple constants |
| // (constantint/constantfp/undef). If there is one non-constant value, |
| // remember the BB it is in. If there is more than one or if *it* is a PHI, |
| // bail out. We don't do arbitrary constant expressions here because moving |
| // their computation can be expensive without a cost model. |
| BasicBlock *NonConstBB = 0; |
| for (unsigned i = 0; i != NumPHIValues; ++i) { |
| Value *InVal = PN->getIncomingValue(i); |
| if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal)) |
| continue; |
| |
| if (isa<PHINode>(InVal)) return 0; // Itself a phi. |
| if (NonConstBB) return 0; // More than one non-const value. |
| |
| NonConstBB = PN->getIncomingBlock(i); |
| |
| // If the InVal is an invoke at the end of the pred block, then we can't |
| // insert a computation after it without breaking the edge. |
| if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) |
| if (II->getParent() == NonConstBB) |
| return 0; |
| |
| // If the incoming non-constant value is in I's block, we will remove one |
| // instruction, but insert another equivalent one, leading to infinite |
| // instcombine. |
| if (NonConstBB == I.getParent()) |
| return 0; |
| } |
| |
| // If there is exactly one non-constant value, we can insert a copy of the |
| // operation in that block. However, if this is a critical edge, we would be |
| // inserting the computation one some other paths (e.g. inside a loop). Only |
| // do this if the pred block is unconditionally branching into the phi block. |
| if (NonConstBB != 0) { |
| BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); |
| if (!BI || !BI->isUnconditional()) return 0; |
| } |
| |
| // Okay, we can do the transformation: create the new PHI node. |
| PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues()); |
| InsertNewInstBefore(NewPN, *PN); |
| NewPN->takeName(PN); |
| |
| // If we are going to have to insert a new computation, do so right before the |
| // predecessors terminator. |
| if (NonConstBB) |
| Builder->SetInsertPoint(NonConstBB->getTerminator()); |
| |
| // Next, add all of the operands to the PHI. |
| if (SelectInst *SI = dyn_cast<SelectInst>(&I)) { |
| // We only currently try to fold the condition of a select when it is a phi, |
| // not the true/false values. |
| Value *TrueV = SI->getTrueValue(); |
| Value *FalseV = SI->getFalseValue(); |
| BasicBlock *PhiTransBB = PN->getParent(); |
| for (unsigned i = 0; i != NumPHIValues; ++i) { |
| BasicBlock *ThisBB = PN->getIncomingBlock(i); |
| Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB); |
| Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB); |
| Value *InV = 0; |
| if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) |
| InV = InC->isNullValue() ? FalseVInPred : TrueVInPred; |
| else |
| InV = Builder->CreateSelect(PN->getIncomingValue(i), |
| TrueVInPred, FalseVInPred, "phitmp"); |
| NewPN->addIncoming(InV, ThisBB); |
| } |
| } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) { |
| Constant *C = cast<Constant>(I.getOperand(1)); |
| for (unsigned i = 0; i != NumPHIValues; ++i) { |
| Value *InV = 0; |
| if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) |
| InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C); |
| else if (isa<ICmpInst>(CI)) |
| InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i), |
| C, "phitmp"); |
| else |
| InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i), |
| C, "phitmp"); |
| NewPN->addIncoming(InV, PN->getIncomingBlock(i)); |
| } |
| } else if (I.getNumOperands() == 2) { |
| Constant *C = cast<Constant>(I.getOperand(1)); |
| for (unsigned i = 0; i != NumPHIValues; ++i) { |
| Value *InV = 0; |
| if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) |
| InV = ConstantExpr::get(I.getOpcode(), InC, C); |
| else |
| InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(), |
| PN->getIncomingValue(i), C, "phitmp"); |
| NewPN->addIncoming(InV, PN->getIncomingBlock(i)); |
| } |
| } else { |
| CastInst *CI = cast<CastInst>(&I); |
| Type *RetTy = CI->getType(); |
| for (unsigned i = 0; i != NumPHIValues; ++i) { |
| Value *InV; |
| if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) |
| InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy); |
| else |
| InV = Builder->CreateCast(CI->getOpcode(), |
| PN->getIncomingValue(i), I.getType(), "phitmp"); |
| NewPN->addIncoming(InV, PN->getIncomingBlock(i)); |
| } |
| } |
| |
| for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); |
| UI != E; ) { |
| Instruction *User = cast<Instruction>(*UI++); |
| if (User == &I) continue; |
| ReplaceInstUsesWith(*User, NewPN); |
| EraseInstFromFunction(*User); |
| } |
| return ReplaceInstUsesWith(I, NewPN); |
| } |
| |
| /// FindElementAtOffset - Given a type and a constant offset, determine whether |
| /// or not there is a sequence of GEP indices into the type that will land us at |
| /// the specified offset. If so, fill them into NewIndices and return the |
| /// resultant element type, otherwise return null. |
| Type *InstCombiner::FindElementAtOffset(Type *Ty, int64_t Offset, |
| SmallVectorImpl<Value*> &NewIndices) { |
| if (!TD) return 0; |
| if (!Ty->isSized()) return 0; |
| |
| // Start with the index over the outer type. Note that the type size |
| // might be zero (even if the offset isn't zero) if the indexed type |
| // is something like [0 x {int, int}] |
| Type *IntPtrTy = TD->getIntPtrType(Ty->getContext()); |
| int64_t FirstIdx = 0; |
| if (int64_t TySize = TD->getTypeAllocSize(Ty)) { |
| FirstIdx = Offset/TySize; |
| Offset -= FirstIdx*TySize; |
| |
| // Handle hosts where % returns negative instead of values [0..TySize). |
| if (Offset < 0) { |
| --FirstIdx; |
| Offset += TySize; |
| assert(Offset >= 0); |
| } |
| assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset"); |
| } |
| |
| NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx)); |
| |
| // Index into the types. If we fail, set OrigBase to null. |
| while (Offset) { |
| // Indexing into tail padding between struct/array elements. |
| if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty)) |
| return 0; |
| |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| const StructLayout *SL = TD->getStructLayout(STy); |
| assert(Offset < (int64_t)SL->getSizeInBytes() && |
| "Offset must stay within the indexed type"); |
| |
| unsigned Elt = SL->getElementContainingOffset(Offset); |
| NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), |
| Elt)); |
| |
| Offset -= SL->getElementOffset(Elt); |
| Ty = STy->getElementType(Elt); |
| } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) { |
| uint64_t EltSize = TD->getTypeAllocSize(AT->getElementType()); |
| assert(EltSize && "Cannot index into a zero-sized array"); |
| NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize)); |
| Offset %= EltSize; |
| Ty = AT->getElementType(); |
| } else { |
| // Otherwise, we can't index into the middle of this atomic type, bail. |
| return 0; |
| } |
| } |
| |
| return Ty; |
| } |
| |
| static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) { |
| // If this GEP has only 0 indices, it is the same pointer as |
| // Src. If Src is not a trivial GEP too, don't combine |
| // the indices. |
| if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() && |
| !Src.hasOneUse()) |
| return false; |
| return true; |
| } |
| |
| /// Descale - Return a value X such that Val = X * Scale, or null if none. If |
| /// the multiplication is known not to overflow then NoSignedWrap is set. |
| Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) { |
| assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!"); |
| assert(cast<IntegerType>(Val->getType())->getBitWidth() == |
| Scale.getBitWidth() && "Scale not compatible with value!"); |
| |
| // If Val is zero or Scale is one then Val = Val * Scale. |
| if (match(Val, m_Zero()) || Scale == 1) { |
| NoSignedWrap = true; |
| return Val; |
| } |
| |
| // If Scale is zero then it does not divide Val. |
| if (Scale.isMinValue()) |
| return 0; |
| |
| // Look through chains of multiplications, searching for a constant that is |
| // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4 |
| // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by |
| // a factor of 4 will produce X*(Y*2). The principle of operation is to bore |
| // down from Val: |
| // |
| // Val = M1 * X || Analysis starts here and works down |
| // M1 = M2 * Y || Doesn't descend into terms with more |
| // M2 = Z * 4 \/ than one use |
| // |
| // Then to modify a term at the bottom: |
| // |
| // Val = M1 * X |
| // M1 = Z * Y || Replaced M2 with Z |
| // |
| // Then to work back up correcting nsw flags. |
| |
| // Op - the term we are currently analyzing. Starts at Val then drills down. |
| // Replaced with its descaled value before exiting from the drill down loop. |
| Value *Op = Val; |
| |
| // Parent - initially null, but after drilling down notes where Op came from. |
| // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the |
| // 0'th operand of Val. |
| std::pair<Instruction*, unsigned> Parent; |
| |
| // RequireNoSignedWrap - Set if the transform requires a descaling at deeper |
| // levels that doesn't overflow. |
| bool RequireNoSignedWrap = false; |
| |
| // logScale - log base 2 of the scale. Negative if not a power of 2. |
| int32_t logScale = Scale.exactLogBase2(); |
| |
| for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down |
| |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) { |
| // If Op is a constant divisible by Scale then descale to the quotient. |
| APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth. |
| APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder); |
| if (!Remainder.isMinValue()) |
| // Not divisible by Scale. |
| return 0; |
| // Replace with the quotient in the parent. |
| Op = ConstantInt::get(CI->getType(), Quotient); |
| NoSignedWrap = true; |
| break; |
| } |
| |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) { |
| |
| if (BO->getOpcode() == Instruction::Mul) { |
| // Multiplication. |
| NoSignedWrap = BO->hasNoSignedWrap(); |
| if (RequireNoSignedWrap && !NoSignedWrap) |
| return 0; |
| |
| // There are three cases for multiplication: multiplication by exactly |
| // the scale, multiplication by a constant different to the scale, and |
| // multiplication by something else. |
| Value *LHS = BO->getOperand(0); |
| Value *RHS = BO->getOperand(1); |
| |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { |
| // Multiplication by a constant. |
| if (CI->getValue() == Scale) { |
| // Multiplication by exactly the scale, replace the multiplication |
| // by its left-hand side in the parent. |
| Op = LHS; |
| break; |
| } |
| |
| // Otherwise drill down into the constant. |
| if (!Op->hasOneUse()) |
| return 0; |
| |
| Parent = std::make_pair(BO, 1); |
| continue; |
| } |
| |
| // Multiplication by something else. Drill down into the left-hand side |
| // since that's where the reassociate pass puts the good stuff. |
| if (!Op->hasOneUse()) |
| return 0; |
| |
| Parent = std::make_pair(BO, 0); |
| continue; |
| } |
| |
| if (logScale > 0 && BO->getOpcode() == Instruction::Shl && |
| isa<ConstantInt>(BO->getOperand(1))) { |
| // Multiplication by a power of 2. |
| NoSignedWrap = BO->hasNoSignedWrap(); |
| if (RequireNoSignedWrap && !NoSignedWrap) |
| return 0; |
| |
| Value *LHS = BO->getOperand(0); |
| int32_t Amt = cast<ConstantInt>(BO->getOperand(1))-> |
| getLimitedValue(Scale.getBitWidth()); |
| // Op = LHS << Amt. |
| |
| if (Amt == logScale) { |
| // Multiplication by exactly the scale, replace the multiplication |
| // by its left-hand side in the parent. |
| Op = LHS; |
| break; |
| } |
| if (Amt < logScale || !Op->hasOneUse()) |
| return 0; |
| |
| // Multiplication by more than the scale. Reduce the multiplying amount |
| // by the scale in the parent. |
| Parent = std::make_pair(BO, 1); |
| Op = ConstantInt::get(BO->getType(), Amt - logScale); |
| break; |
| } |
| } |
| |
| if (!Op->hasOneUse()) |
| return 0; |
| |
| if (CastInst *Cast = dyn_cast<CastInst>(Op)) { |
| if (Cast->getOpcode() == Instruction::SExt) { |
| // Op is sign-extended from a smaller type, descale in the smaller type. |
| unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); |
| APInt SmallScale = Scale.trunc(SmallSize); |
| // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to |
| // descale Op as (sext Y) * Scale. In order to have |
| // sext (Y * SmallScale) = (sext Y) * Scale |
| // some conditions need to hold however: SmallScale must sign-extend to |
| // Scale and the multiplication Y * SmallScale should not overflow. |
| if (SmallScale.sext(Scale.getBitWidth()) != Scale) |
| // SmallScale does not sign-extend to Scale. |
| return 0; |
| assert(SmallScale.exactLogBase2() == logScale); |
| // Require that Y * SmallScale must not overflow. |
| RequireNoSignedWrap = true; |
| |
| // Drill down through the cast. |
| Parent = std::make_pair(Cast, 0); |
| Scale = SmallScale; |
| continue; |
| } |
| |
| if (Cast->getOpcode() == Instruction::Trunc) { |
| // Op is truncated from a larger type, descale in the larger type. |
| // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then |
| // trunc (Y * sext Scale) = (trunc Y) * Scale |
| // always holds. However (trunc Y) * Scale may overflow even if |
| // trunc (Y * sext Scale) does not, so nsw flags need to be cleared |
| // from this point up in the expression (see later). |
| if (RequireNoSignedWrap) |
| return 0; |
| |
| // Drill down through the cast. |
| unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); |
| Parent = std::make_pair(Cast, 0); |
| Scale = Scale.sext(LargeSize); |
| if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits()) |
| logScale = -1; |
| assert(Scale.exactLogBase2() == logScale); |
| continue; |
| } |
| } |
| |
| // Unsupported expression, bail out. |
| return 0; |
| } |
| |
| // We know that we can successfully descale, so from here on we can safely |
| // modify the IR. Op holds the descaled version of the deepest term in the |
| // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known |
| // not to overflow. |
| |
| if (!Parent.first) |
| // The expression only had one term. |
| return Op; |
| |
| // Rewrite the parent using the descaled version of its operand. |
| assert(Parent.first->hasOneUse() && "Drilled down when more than one use!"); |
| assert(Op != Parent.first->getOperand(Parent.second) && |
| "Descaling was a no-op?"); |
| Parent.first->setOperand(Parent.second, Op); |
| Worklist.Add(Parent.first); |
| |
| // Now work back up the expression correcting nsw flags. The logic is based |
| // on the following observation: if X * Y is known not to overflow as a signed |
| // multiplication, and Y is replaced by a value Z with smaller absolute value, |
| // then X * Z will not overflow as a signed multiplication either. As we work |
| // our way up, having NoSignedWrap 'true' means that the descaled value at the |
| // current level has strictly smaller absolute value than the original. |
| Instruction *Ancestor = Parent.first; |
| do { |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) { |
| // If the multiplication wasn't nsw then we can't say anything about the |
| // value of the descaled multiplication, and we have to clear nsw flags |
| // from this point on up. |
| bool OpNoSignedWrap = BO->hasNoSignedWrap(); |
| NoSignedWrap &= OpNoSignedWrap; |
| if (NoSignedWrap != OpNoSignedWrap) { |
| BO->setHasNoSignedWrap(NoSignedWrap); |
| Worklist.Add(Ancestor); |
| } |
| } else if (Ancestor->getOpcode() == Instruction::Trunc) { |
| // The fact that the descaled input to the trunc has smaller absolute |
| // value than the original input doesn't tell us anything useful about |
| // the absolute values of the truncations. |
| NoSignedWrap = false; |
| } |
| assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) && |
| "Failed to keep proper track of nsw flags while drilling down?"); |
| |
| if (Ancestor == Val) |
| // Got to the top, all done! |
| return Val; |
| |
| // Move up one level in the expression. |
| assert(Ancestor->hasOneUse() && "Drilled down when more than one use!"); |
| Ancestor = Ancestor->use_back(); |
| } while (1); |
| } |
| |
| Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { |
| SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); |
| |
| if (Value *V = SimplifyGEPInst(Ops, TD)) |
| return ReplaceInstUsesWith(GEP, V); |
| |
| Value *PtrOp = GEP.getOperand(0); |
| |
| // Eliminate unneeded casts for indices, and replace indices which displace |
| // by multiples of a zero size type with zero. |
| if (TD) { |
| bool MadeChange = false; |
| Type *IntPtrTy = TD->getIntPtrType(GEP.getPointerOperandType()); |
| |
| gep_type_iterator GTI = gep_type_begin(GEP); |
| for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); |
| I != E; ++I, ++GTI) { |
| // Skip indices into struct types. |
| SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI); |
| if (!SeqTy) continue; |
| |
| // If the element type has zero size then any index over it is equivalent |
| // to an index of zero, so replace it with zero if it is not zero already. |
| if (SeqTy->getElementType()->isSized() && |
| TD->getTypeAllocSize(SeqTy->getElementType()) == 0) |
| if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { |
| *I = Constant::getNullValue(IntPtrTy); |
| MadeChange = true; |
| } |
| |
| Type *IndexTy = (*I)->getType(); |
| if (IndexTy != IntPtrTy) { |
| // If we are using a wider index than needed for this platform, shrink |
| // it to what we need. If narrower, sign-extend it to what we need. |
| // This explicit cast can make subsequent optimizations more obvious. |
| *I = Builder->CreateIntCast(*I, IntPtrTy, true); |
| MadeChange = true; |
| } |
| } |
| if (MadeChange) return &GEP; |
| } |
| |
| // Combine Indices - If the source pointer to this getelementptr instruction |
| // is a getelementptr instruction, combine the indices of the two |
| // getelementptr instructions into a single instruction. |
| // |
| if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) { |
| if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src)) |
| return 0; |
| |
| // Note that if our source is a gep chain itself then we wait for that |
| // chain to be resolved before we perform this transformation. This |
| // avoids us creating a TON of code in some cases. |
| if (GEPOperator *SrcGEP = |
| dyn_cast<GEPOperator>(Src->getOperand(0))) |
| if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP)) |
| return 0; // Wait until our source is folded to completion. |
| |
| SmallVector<Value*, 8> Indices; |
| |
| // Find out whether the last index in the source GEP is a sequential idx. |
| bool EndsWithSequential = false; |
| for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src); |
| I != E; ++I) |
| EndsWithSequential = !(*I)->isStructTy(); |
| |
| // Can we combine the two pointer arithmetics offsets? |
| if (EndsWithSequential) { |
| // Replace: gep (gep %P, long B), long A, ... |
| // With: T = long A+B; gep %P, T, ... |
| // |
| Value *Sum; |
| Value *SO1 = Src->getOperand(Src->getNumOperands()-1); |
| Value *GO1 = GEP.getOperand(1); |
| if (SO1 == Constant::getNullValue(SO1->getType())) { |
| Sum = GO1; |
| } else if (GO1 == Constant::getNullValue(GO1->getType())) { |
| Sum = SO1; |
| } else { |
| // If they aren't the same type, then the input hasn't been processed |
| // by the loop above yet (which canonicalizes sequential index types to |
| // intptr_t). Just avoid transforming this until the input has been |
| // normalized. |
| if (SO1->getType() != GO1->getType()) |
| return 0; |
| Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum"); |
| } |
| |
| // Update the GEP in place if possible. |
| if (Src->getNumOperands() == 2) { |
| GEP.setOperand(0, Src->getOperand(0)); |
| GEP.setOperand(1, Sum); |
| return &GEP; |
| } |
| Indices.append(Src->op_begin()+1, Src->op_end()-1); |
| Indices.push_back(Sum); |
| Indices.append(GEP.op_begin()+2, GEP.op_end()); |
| } else if (isa<Constant>(*GEP.idx_begin()) && |
| cast<Constant>(*GEP.idx_begin())->isNullValue() && |
| Src->getNumOperands() != 1) { |
| // Otherwise we can do the fold if the first index of the GEP is a zero |
| Indices.append(Src->op_begin()+1, Src->op_end()); |
| Indices.append(GEP.idx_begin()+1, GEP.idx_end()); |
| } |
| |
| if (!Indices.empty()) |
| return (GEP.isInBounds() && Src->isInBounds()) ? |
| GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices, |
| GEP.getName()) : |
| GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName()); |
| } |
| |
| // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). |
| Value *StrippedPtr = PtrOp->stripPointerCasts(); |
| PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType()); |
| |
| // We do not handle pointer-vector geps here. |
| if (!StrippedPtrTy) |
| return 0; |
| |
| if (StrippedPtr != PtrOp && |
| StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) { |
| |
| bool HasZeroPointerIndex = false; |
| if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1))) |
| HasZeroPointerIndex = C->isZero(); |
| |
| // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... |
| // into : GEP [10 x i8]* X, i32 0, ... |
| // |
| // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ... |
| // into : GEP i8* X, ... |
| // |
| // This occurs when the program declares an array extern like "int X[];" |
| if (HasZeroPointerIndex) { |
| PointerType *CPTy = cast<PointerType>(PtrOp->getType()); |
| if (ArrayType *CATy = |
| dyn_cast<ArrayType>(CPTy->getElementType())) { |
| // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ? |
| if (CATy->getElementType() == StrippedPtrTy->getElementType()) { |
| // -> GEP i8* X, ... |
| SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end()); |
| GetElementPtrInst *Res = |
| GetElementPtrInst::Create(StrippedPtr, Idx, GEP.getName()); |
| Res->setIsInBounds(GEP.isInBounds()); |
| return Res; |
| } |
| |
| if (ArrayType *XATy = |
| dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){ |
| // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ? |
| if (CATy->getElementType() == XATy->getElementType()) { |
| // -> GEP [10 x i8]* X, i32 0, ... |
| // At this point, we know that the cast source type is a pointer |
| // to an array of the same type as the destination pointer |
| // array. Because the array type is never stepped over (there |
| // is a leading zero) we can fold the cast into this GEP. |
| GEP.setOperand(0, StrippedPtr); |
| return &GEP; |
| } |
| } |
| } |
| } else if (GEP.getNumOperands() == 2) { |
| // Transform things like: |
| // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V |
| // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast |
| Type *SrcElTy = StrippedPtrTy->getElementType(); |
| Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType(); |
| if (TD && SrcElTy->isArrayTy() && |
| TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) == |
| TD->getTypeAllocSize(ResElTy)) { |
| Value *Idx[2]; |
| Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); |
| Idx[1] = GEP.getOperand(1); |
| Value *NewGEP = GEP.isInBounds() ? |
| Builder->CreateInBoundsGEP(StrippedPtr, Idx, GEP.getName()) : |
| Builder->CreateGEP(StrippedPtr, Idx, GEP.getName()); |
| // V and GEP are both pointer types --> BitCast |
| return new BitCastInst(NewGEP, GEP.getType()); |
| } |
| |
| // Transform things like: |
| // %V = mul i64 %N, 4 |
| // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V |
| // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast |
| if (TD && ResElTy->isSized() && SrcElTy->isSized()) { |
| // Check that changing the type amounts to dividing the index by a scale |
| // factor. |
| uint64_t ResSize = TD->getTypeAllocSize(ResElTy); |
| uint64_t SrcSize = TD->getTypeAllocSize(SrcElTy); |
| if (ResSize && SrcSize % ResSize == 0) { |
| Value *Idx = GEP.getOperand(1); |
| unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); |
| uint64_t Scale = SrcSize / ResSize; |
| |
| // Earlier transforms ensure that the index has type IntPtrType, which |
| // considerably simplifies the logic by eliminating implicit casts. |
| assert(Idx->getType() == TD->getIntPtrType(GEP.getContext()) && |
| "Index not cast to pointer width?"); |
| |
| bool NSW; |
| if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { |
| // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. |
| // If the multiplication NewIdx * Scale may overflow then the new |
| // GEP may not be "inbounds". |
| Value *NewGEP = GEP.isInBounds() && NSW ? |
| Builder->CreateInBoundsGEP(StrippedPtr, NewIdx, GEP.getName()) : |
| Builder->CreateGEP(StrippedPtr, NewIdx, GEP.getName()); |
| // The NewGEP must be pointer typed, so must the old one -> BitCast |
| return new BitCastInst(NewGEP, GEP.getType()); |
| } |
| } |
| } |
| |
| // Similarly, transform things like: |
| // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp |
| // (where tmp = 8*tmp2) into: |
| // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast |
| if (TD && ResElTy->isSized() && SrcElTy->isSized() && |
| SrcElTy->isArrayTy()) { |
| // Check that changing to the array element type amounts to dividing the |
| // index by a scale factor. |
| uint64_t ResSize = TD->getTypeAllocSize(ResElTy); |
| uint64_t ArrayEltSize = |
| TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()); |
| if (ResSize && ArrayEltSize % ResSize == 0) { |
| Value *Idx = GEP.getOperand(1); |
| unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); |
| uint64_t Scale = ArrayEltSize / ResSize; |
| |
| // Earlier transforms ensure that the index has type IntPtrType, which |
| // considerably simplifies the logic by eliminating implicit casts. |
| assert(Idx->getType() == TD->getIntPtrType(GEP.getContext()) && |
| "Index not cast to pointer width?"); |
| |
| bool NSW; |
| if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { |
| // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. |
| // If the multiplication NewIdx * Scale may overflow then the new |
| // GEP may not be "inbounds". |
| Value *Off[2]; |
| Off[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); |
| Off[1] = NewIdx; |
| Value *NewGEP = GEP.isInBounds() && NSW ? |
| Builder->CreateInBoundsGEP(StrippedPtr, Off, GEP.getName()) : |
| Builder->CreateGEP(StrippedPtr, Off, GEP.getName()); |
| // The NewGEP must be pointer typed, so must the old one -> BitCast |
| return new BitCastInst(NewGEP, GEP.getType()); |
| } |
| } |
| } |
| } |
| } |
| |
| /// See if we can simplify: |
| /// X = bitcast A* to B* |
| /// Y = gep X, <...constant indices...> |
| /// into a gep of the original struct. This is important for SROA and alias |
| /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged. |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) { |
| if (TD && |
| !isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices() && |
| StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) { |
| |
| // Determine how much the GEP moves the pointer. |
| SmallVector<Value*, 8> Ops(GEP.idx_begin(), GEP.idx_end()); |
| int64_t Offset = TD->getIndexedOffset(GEP.getPointerOperandType(), Ops); |
| |
| // If this GEP instruction doesn't move the pointer, just replace the GEP |
| // with a bitcast of the real input to the dest type. |
| if (Offset == 0) { |
| // If the bitcast is of an allocation, and the allocation will be |
| // converted to match the type of the cast, don't touch this. |
| if (isa<AllocaInst>(BCI->getOperand(0)) || |
| isAllocationFn(BCI->getOperand(0), TLI)) { |
| // See if the bitcast simplifies, if so, don't nuke this GEP yet. |
| if (Instruction *I = visitBitCast(*BCI)) { |
| if (I != BCI) { |
| I->takeName(BCI); |
| BCI->getParent()->getInstList().insert(BCI, I); |
| ReplaceInstUsesWith(*BCI, I); |
| } |
| return &GEP; |
| } |
| } |
| return new BitCastInst(BCI->getOperand(0), GEP.getType()); |
| } |
| |
| // Otherwise, if the offset is non-zero, we need to find out if there is a |
| // field at Offset in 'A's type. If so, we can pull the cast through the |
| // GEP. |
| SmallVector<Value*, 8> NewIndices; |
| Type *InTy = |
| cast<PointerType>(BCI->getOperand(0)->getType())->getElementType(); |
| if (FindElementAtOffset(InTy, Offset, NewIndices)) { |
| Value *NGEP = GEP.isInBounds() ? |
| Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices) : |
| Builder->CreateGEP(BCI->getOperand(0), NewIndices); |
| |
| if (NGEP->getType() == GEP.getType()) |
| return ReplaceInstUsesWith(GEP, NGEP); |
| NGEP->takeName(&GEP); |
| return new BitCastInst(NGEP, GEP.getType()); |
| } |
| } |
| } |
| |
| return 0; |
| } |
| |
| |
| |
| static bool |
| isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users, |
| const TargetLibraryInfo *TLI) { |
| SmallVector<Instruction*, 4> Worklist; |
| Worklist.push_back(AI); |
| |
| do { |
| Instruction *PI = Worklist.pop_back_val(); |
| for (Value::use_iterator UI = PI->use_begin(), UE = PI->use_end(); UI != UE; |
| ++UI) { |
| Instruction *I = cast<Instruction>(*UI); |
| switch (I->getOpcode()) { |
| default: |
| // Give up the moment we see something we can't handle. |
| return false; |
| |
| case Instruction::BitCast: |
| case Instruction::GetElementPtr: |
| Users.push_back(I); |
| Worklist.push_back(I); |
| continue; |
| |
| case Instruction::ICmp: { |
| ICmpInst *ICI = cast<ICmpInst>(I); |
| // We can fold eq/ne comparisons with null to false/true, respectively. |
| if (!ICI->isEquality() || !isa<ConstantPointerNull>(ICI->getOperand(1))) |
| return false; |
| Users.push_back(I); |
| continue; |
| } |
| |
| case Instruction::Call: |
| // Ignore no-op and store intrinsics. |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { |
| switch (II->getIntrinsicID()) { |
| default: |
| return false; |
| |
| case Intrinsic::memmove: |
| case Intrinsic::memcpy: |
| case Intrinsic::memset: { |
| MemIntrinsic *MI = cast<MemIntrinsic>(II); |
| if (MI->isVolatile() || MI->getRawDest() != PI) |
| return false; |
| } |
| // fall through |
| case Intrinsic::dbg_declare: |
| case Intrinsic::dbg_value: |
| case Intrinsic::invariant_start: |
| case Intrinsic::invariant_end: |
| case Intrinsic::lifetime_start: |
| case Intrinsic::lifetime_end: |
| case Intrinsic::objectsize: |
| Users.push_back(I); |
| continue; |
| } |
| } |
| |
| if (isFreeCall(I, TLI)) { |
| Users.push_back(I); |
| continue; |
| } |
| return false; |
| |
| case Instruction::Store: { |
| StoreInst *SI = cast<StoreInst>(I); |
| if (SI->isVolatile() || SI->getPointerOperand() != PI) |
| return false; |
| Users.push_back(I); |
| continue; |
| } |
| } |
| llvm_unreachable("missing a return?"); |
| } |
| } while (!Worklist.empty()); |
| return true; |
| } |
| |
| Instruction *InstCombiner::visitAllocSite(Instruction &MI) { |
| // If we have a malloc call which is only used in any amount of comparisons |
| // to null and free calls, delete the calls and replace the comparisons with |
| // true or false as appropriate. |
| SmallVector<WeakVH, 64> Users; |
| if (isAllocSiteRemovable(&MI, Users, TLI)) { |
| for (unsigned i = 0, e = Users.size(); i != e; ++i) { |
| Instruction *I = cast_or_null<Instruction>(&*Users[i]); |
| if (!I) continue; |
| |
| if (ICmpInst *C = dyn_cast<ICmpInst>(I)) { |
| ReplaceInstUsesWith(*C, |
| ConstantInt::get(Type::getInt1Ty(C->getContext()), |
| C->isFalseWhenEqual())); |
| } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) { |
| ReplaceInstUsesWith(*I, UndefValue::get(I->getType())); |
| } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { |
| if (II->getIntrinsicID() == Intrinsic::objectsize) { |
| ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1)); |
| uint64_t DontKnow = CI->isZero() ? -1ULL : 0; |
| ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow)); |
| } |
| } |
| EraseInstFromFunction(*I); |
| } |
| |
| if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) { |
| // Replace invoke with a NOP intrinsic to maintain the original CFG |
| Module *M = II->getParent()->getParent()->getParent(); |
| Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing); |
| InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(), |
| ArrayRef<Value *>(), "", II->getParent()); |
| } |
| return EraseInstFromFunction(MI); |
| } |
| return 0; |
| } |
| |
| |
| |
| Instruction *InstCombiner::visitFree(CallInst &FI) { |
| Value *Op = FI.getArgOperand(0); |
| |
| // free undef -> unreachable. |
| if (isa<UndefValue>(Op)) { |
| // Insert a new store to null because we cannot modify the CFG here. |
| Builder->CreateStore(ConstantInt::getTrue(FI.getContext()), |
| UndefValue::get(Type::getInt1PtrTy(FI.getContext()))); |
| return EraseInstFromFunction(FI); |
| } |
| |
| // If we have 'free null' delete the instruction. This can happen in stl code |
| // when lots of inlining happens. |
| if (isa<ConstantPointerNull>(Op)) |
| return EraseInstFromFunction(FI); |
| |
| return 0; |
| } |
| |
| |
| |
| Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { |
| // Change br (not X), label True, label False to: br X, label False, True |
| Value *X = 0; |
| BasicBlock *TrueDest; |
| BasicBlock *FalseDest; |
| if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) && |
| !isa<Constant>(X)) { |
| // Swap Destinations and condition... |
| BI.setCondition(X); |
| BI.swapSuccessors(); |
| return &BI; |
| } |
| |
| // Cannonicalize fcmp_one -> fcmp_oeq |
| FCmpInst::Predicate FPred; Value *Y; |
| if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)), |
| TrueDest, FalseDest)) && |
| BI.getCondition()->hasOneUse()) |
| if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE || |
| FPred == FCmpInst::FCMP_OGE) { |
| FCmpInst *Cond = cast<FCmpInst>(BI.getCondition()); |
| Cond->setPredicate(FCmpInst::getInversePredicate(FPred)); |
| |
| // Swap Destinations and condition. |
| BI.swapSuccessors(); |
| Worklist.Add(Cond); |
| return &BI; |
| } |
| |
| // Cannonicalize icmp_ne -> icmp_eq |
| ICmpInst::Predicate IPred; |
| if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)), |
| TrueDest, FalseDest)) && |
| BI.getCondition()->hasOneUse()) |
| if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE || |
| IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE || |
| IPred == ICmpInst::ICMP_SGE) { |
| ICmpInst *Cond = cast<ICmpInst>(BI.getCondition()); |
| Cond->setPredicate(ICmpInst::getInversePredicate(IPred)); |
| // Swap Destinations and condition. |
| BI.swapSuccessors(); |
| Worklist.Add(Cond); |
| return &BI; |
| } |
| |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { |
| Value *Cond = SI.getCondition(); |
| if (Instruction *I = dyn_cast<Instruction>(Cond)) { |
| if (I->getOpcode() == Instruction::Add) |
| if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) { |
| // change 'switch (X+4) case 1:' into 'switch (X) case -3' |
| // Skip the first item since that's the default case. |
| for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end(); |
| i != e; ++i) { |
| ConstantInt* CaseVal = i.getCaseValue(); |
| Constant* NewCaseVal = ConstantExpr::getSub(cast<Constant>(CaseVal), |
| AddRHS); |
| assert(isa<ConstantInt>(NewCaseVal) && |
| "Result of expression should be constant"); |
| i.setValue(cast<ConstantInt>(NewCaseVal)); |
| } |
| SI.setCondition(I->getOperand(0)); |
| Worklist.Add(I); |
| return &SI; |
| } |
| } |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { |
| Value *Agg = EV.getAggregateOperand(); |
| |
| if (!EV.hasIndices()) |
| return ReplaceInstUsesWith(EV, Agg); |
| |
| if (Constant *C = dyn_cast<Constant>(Agg)) { |
| if (Constant *C2 = C->getAggregateElement(*EV.idx_begin())) { |
| if (EV.getNumIndices() == 0) |
| return ReplaceInstUsesWith(EV, C2); |
| // Extract the remaining indices out of the constant indexed by the |
| // first index |
| return ExtractValueInst::Create(C2, EV.getIndices().slice(1)); |
| } |
| return 0; // Can't handle other constants |
| } |
| |
| if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) { |
| // We're extracting from an insertvalue instruction, compare the indices |
| const unsigned *exti, *exte, *insi, *inse; |
| for (exti = EV.idx_begin(), insi = IV->idx_begin(), |
| exte = EV.idx_end(), inse = IV->idx_end(); |
| exti != exte && insi != inse; |
| ++exti, ++insi) { |
| if (*insi != *exti) |
| // The insert and extract both reference distinctly different elements. |
| // This means the extract is not influenced by the insert, and we can |
| // replace the aggregate operand of the extract with the aggregate |
| // operand of the insert. i.e., replace |
| // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 |
| // %E = extractvalue { i32, { i32 } } %I, 0 |
| // with |
| // %E = extractvalue { i32, { i32 } } %A, 0 |
| return ExtractValueInst::Create(IV->getAggregateOperand(), |
| EV.getIndices()); |
| } |
| if (exti == exte && insi == inse) |
| // Both iterators are at the end: Index lists are identical. Replace |
| // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 |
| // %C = extractvalue { i32, { i32 } } %B, 1, 0 |
| // with "i32 42" |
| return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand()); |
| if (exti == exte) { |
| // The extract list is a prefix of the insert list. i.e. replace |
| // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 |
| // %E = extractvalue { i32, { i32 } } %I, 1 |
| // with |
| // %X = extractvalue { i32, { i32 } } %A, 1 |
| // %E = insertvalue { i32 } %X, i32 42, 0 |
| // by switching the order of the insert and extract (though the |
| // insertvalue should be left in, since it may have other uses). |
| Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(), |
| EV.getIndices()); |
| return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), |
| makeArrayRef(insi, inse)); |
| } |
| if (insi == inse) |
| // The insert list is a prefix of the extract list |
| // We can simply remove the common indices from the extract and make it |
| // operate on the inserted value instead of the insertvalue result. |
| // i.e., replace |
| // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 |
| // %E = extractvalue { i32, { i32 } } %I, 1, 0 |
| // with |
| // %E extractvalue { i32 } { i32 42 }, 0 |
| return ExtractValueInst::Create(IV->getInsertedValueOperand(), |
| makeArrayRef(exti, exte)); |
| } |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) { |
| // We're extracting from an intrinsic, see if we're the only user, which |
| // allows us to simplify multiple result intrinsics to simpler things that |
| // just get one value. |
| if (II->hasOneUse()) { |
| // Check if we're grabbing the overflow bit or the result of a 'with |
| // overflow' intrinsic. If it's the latter we can remove the intrinsic |
| // and replace it with a traditional binary instruction. |
| switch (II->getIntrinsicID()) { |
| case Intrinsic::uadd_with_overflow: |
| case Intrinsic::sadd_with_overflow: |
| if (*EV.idx_begin() == 0) { // Normal result. |
| Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); |
| ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); |
| EraseInstFromFunction(*II); |
| return BinaryOperator::CreateAdd(LHS, RHS); |
| } |
| |
| // If the normal result of the add is dead, and the RHS is a constant, |
| // we can transform this into a range comparison. |
| // overflow = uadd a, -4 --> overflow = icmp ugt a, 3 |
| if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1))) |
| return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0), |
| ConstantExpr::getNot(CI)); |
| break; |
| case Intrinsic::usub_with_overflow: |
| case Intrinsic::ssub_with_overflow: |
| if (*EV.idx_begin() == 0) { // Normal result. |
| Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); |
| ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); |
| EraseInstFromFunction(*II); |
| return BinaryOperator::CreateSub(LHS, RHS); |
| } |
| break; |
| case Intrinsic::umul_with_overflow: |
| case Intrinsic::smul_with_overflow: |
| if (*EV.idx_begin() == 0) { // Normal result. |
| Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); |
| ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); |
| EraseInstFromFunction(*II); |
| return BinaryOperator::CreateMul(LHS, RHS); |
| } |
| break; |
| default: |
| break; |
| } |
| } |
| } |
| if (LoadInst *L = dyn_cast<LoadInst>(Agg)) |
| // If the (non-volatile) load only has one use, we can rewrite this to a |
| // load from a GEP. This reduces the size of the load. |
| // FIXME: If a load is used only by extractvalue instructions then this |
| // could be done regardless of having multiple uses. |
| if (L->isSimple() && L->hasOneUse()) { |
| // extractvalue has integer indices, getelementptr has Value*s. Convert. |
| SmallVector<Value*, 4> Indices; |
| // Prefix an i32 0 since we need the first element. |
| Indices.push_back(Builder->getInt32(0)); |
| for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end(); |
| I != E; ++I) |
| Indices.push_back(Builder->getInt32(*I)); |
| |
| // We need to insert these at the location of the old load, not at that of |
| // the extractvalue. |
| Builder->SetInsertPoint(L->getParent(), L); |
| Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), Indices); |
| // Returning the load directly will cause the main loop to insert it in |
| // the wrong spot, so use ReplaceInstUsesWith(). |
| return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP)); |
| } |
| // We could simplify extracts from other values. Note that nested extracts may |
| // already be simplified implicitly by the above: extract (extract (insert) ) |
| // will be translated into extract ( insert ( extract ) ) first and then just |
| // the value inserted, if appropriate. Similarly for extracts from single-use |
| // loads: extract (extract (load)) will be translated to extract (load (gep)) |
| // and if again single-use then via load (gep (gep)) to load (gep). |
| // However, double extracts from e.g. function arguments or return values |
| // aren't handled yet. |
| return 0; |
| } |
| |
| enum Personality_Type { |
| Unknown_Personality, |
| GNU_Ada_Personality, |
| GNU_CXX_Personality, |
| GNU_ObjC_Personality |
| }; |
| |
| /// RecognizePersonality - See if the given exception handling personality |
| /// function is one that we understand. If so, return a description of it; |
| /// otherwise return Unknown_Personality. |
| static Personality_Type RecognizePersonality(Value *Pers) { |
| Function *F = dyn_cast<Function>(Pers->stripPointerCasts()); |
| if (!F) |
| return Unknown_Personality; |
| return StringSwitch<Personality_Type>(F->getName()) |
| .Case("__gnat_eh_personality", GNU_Ada_Personality) |
| .Case("__gxx_personality_v0", GNU_CXX_Personality) |
| .Case("__objc_personality_v0", GNU_ObjC_Personality) |
| .Default(Unknown_Personality); |
| } |
| |
| /// isCatchAll - Return 'true' if the given typeinfo will match anything. |
| static bool isCatchAll(Personality_Type Personality, Constant *TypeInfo) { |
| switch (Personality) { |
| case Unknown_Personality: |
| return false; |
| case GNU_Ada_Personality: |
| // While __gnat_all_others_value will match any Ada exception, it doesn't |
| // match foreign exceptions (or didn't, before gcc-4.7). |
| return false; |
| case GNU_CXX_Personality: |
| case GNU_ObjC_Personality: |
| return TypeInfo->isNullValue(); |
| } |
| llvm_unreachable("Unknown personality!"); |
| } |
| |
| static bool shorter_filter(const Value *LHS, const Value *RHS) { |
| return |
| cast<ArrayType>(LHS->getType())->getNumElements() |
| < |
| cast<ArrayType>(RHS->getType())->getNumElements(); |
| } |
| |
| Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) { |
| // The logic here should be correct for any real-world personality function. |
| // However if that turns out not to be true, the offending logic can always |
| // be conditioned on the personality function, like the catch-all logic is. |
| Personality_Type Personality = RecognizePersonality(LI.getPersonalityFn()); |
| |
| // Simplify the list of clauses, eg by removing repeated catch clauses |
| // (these are often created by inlining). |
| bool MakeNewInstruction = false; // If true, recreate using the following: |
| SmallVector<Value *, 16> NewClauses; // - Clauses for the new instruction; |
| bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup. |
| |
| SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already. |
| for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) { |
| bool isLastClause = i + 1 == e; |
| if (LI.isCatch(i)) { |
| // A catch clause. |
| Value *CatchClause = LI.getClause(i); |
| Constant *TypeInfo = cast<Constant>(CatchClause->stripPointerCasts()); |
| |
| // If we already saw this clause, there is no point in having a second |
| // copy of it. |
| if (AlreadyCaught.insert(TypeInfo)) { |
| // This catch clause was not already seen. |
| NewClauses.push_back(CatchClause); |
| } else { |
| // Repeated catch clause - drop the redundant copy. |
| MakeNewInstruction = true; |
| } |
| |
| // If this is a catch-all then there is no point in keeping any following |
| // clauses or marking the landingpad as having a cleanup. |
| if (isCatchAll(Personality, TypeInfo)) { |
| if (!isLastClause) |
| MakeNewInstruction = true; |
| CleanupFlag = false; |
| break; |
| } |
| } else { |
| // A filter clause. If any of the filter elements were already caught |
| // then they can be dropped from the filter. It is tempting to try to |
| // exploit the filter further by saying that any typeinfo that does not |
| // occur in the filter can't be caught later (and thus can be dropped). |
| // However this would be wrong, since typeinfos can match without being |
| // equal (for example if one represents a C++ class, and the other some |
| // class derived from it). |
| assert(LI.isFilter(i) && "Unsupported landingpad clause!"); |
| Value *FilterClause = LI.getClause(i); |
| ArrayType *FilterType = cast<ArrayType>(FilterClause->getType()); |
| unsigned NumTypeInfos = FilterType->getNumElements(); |
| |
| // An empty filter catches everything, so there is no point in keeping any |
| // following clauses or marking the landingpad as having a cleanup. By |
| // dealing with this case here the following code is made a bit simpler. |
| if (!NumTypeInfos) { |
| NewClauses.push_back(FilterClause); |
| if (!isLastClause) |
| MakeNewInstruction = true; |
| CleanupFlag = false; |
| break; |
| } |
| |
| bool MakeNewFilter = false; // If true, make a new filter. |
| SmallVector<Constant *, 16> NewFilterElts; // New elements. |
| if (isa<ConstantAggregateZero>(FilterClause)) { |
| // Not an empty filter - it contains at least one null typeinfo. |
| assert(NumTypeInfos > 0 && "Should have handled empty filter already!"); |
| Constant *TypeInfo = |
| Constant::getNullValue(FilterType->getElementType()); |
| // If this typeinfo is a catch-all then the filter can never match. |
| if (isCatchAll(Personality, TypeInfo)) { |
| // Throw the filter away. |
| MakeNewInstruction = true; |
| continue; |
| } |
| |
| // There is no point in having multiple copies of this typeinfo, so |
| // discard all but the first copy if there is more than one. |
| NewFilterElts.push_back(TypeInfo); |
| if (NumTypeInfos > 1) |
| MakeNewFilter = true; |
| } else { |
| ConstantArray *Filter = cast<ConstantArray>(FilterClause); |
| SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements. |
| NewFilterElts.reserve(NumTypeInfos); |
| |
| // Remove any filter elements that were already caught or that already |
| // occurred in the filter. While there, see if any of the elements are |
| // catch-alls. If so, the filter can be discarded. |
| bool SawCatchAll = false; |
| for (unsigned j = 0; j != NumTypeInfos; ++j) { |
| Value *Elt = Filter->getOperand(j); |
| Constant *TypeInfo = cast<Constant>(Elt->stripPointerCasts()); |
| if (isCatchAll(Personality, TypeInfo)) { |
| // This element is a catch-all. Bail out, noting this fact. |
| SawCatchAll = true; |
| break; |
| } |
| if (AlreadyCaught.count(TypeInfo)) |
| // Already caught by an earlier clause, so having it in the filter |
| // is pointless. |
| continue; |
| // There is no point in having multiple copies of the same typeinfo in |
| // a filter, so only add it if we didn't already. |
| if (SeenInFilter.insert(TypeInfo)) |
| NewFilterElts.push_back(cast<Constant>(Elt)); |
| } |
| // A filter containing a catch-all cannot match anything by definition. |
| if (SawCatchAll) { |
| // Throw the filter away. |
| MakeNewInstruction = true; |
| continue; |
| } |
| |
| // If we dropped something from the filter, make a new one. |
| if (NewFilterElts.size() < NumTypeInfos) |
| MakeNewFilter = true; |
| } |
| if (MakeNewFilter) { |
| FilterType = ArrayType::get(FilterType->getElementType(), |
| NewFilterElts.size()); |
| FilterClause = ConstantArray::get(FilterType, NewFilterElts); |
| MakeNewInstruction = true; |
| } |
| |
| NewClauses.push_back(FilterClause); |
| |
| // If the new filter is empty then it will catch everything so there is |
| // no point in keeping any following clauses or marking the landingpad |
| // as having a cleanup. The case of the original filter being empty was |
| // already handled above. |
| if (MakeNewFilter && !NewFilterElts.size()) { |
| assert(MakeNewInstruction && "New filter but not a new instruction!"); |
| CleanupFlag = false; |
| break; |
| } |
| } |
| } |
| |
| // If several filters occur in a row then reorder them so that the shortest |
| // filters come first (those with the smallest number of elements). This is |
| // advantageous because shorter filters are more likely to match, speeding up |
| // unwinding, but mostly because it increases the effectiveness of the other |
| // filter optimizations below. |
| for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) { |
| unsigned j; |
| // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters. |
| for (j = i; j != e; ++j) |
| if (!isa<ArrayType>(NewClauses[j]->getType())) |
| break; |
| |
| // Check whether the filters are already sorted by length. We need to know |
| // if sorting them is actually going to do anything so that we only make a |
| // new landingpad instruction if it does. |
| for (unsigned k = i; k + 1 < j; ++k) |
| if (shorter_filter(NewClauses[k+1], NewClauses[k])) { |
| // Not sorted, so sort the filters now. Doing an unstable sort would be |
| // correct too but reordering filters pointlessly might confuse users. |
| std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j, |
| shorter_filter); |
| MakeNewInstruction = true; |
| break; |
| } |
| |
| // Look for the next batch of filters. |
| i = j + 1; |
| } |
| |
| // If typeinfos matched if and only if equal, then the elements of a filter L |
| // that occurs later than a filter F could be replaced by the intersection of |
| // the elements of F and L. In reality two typeinfos can match without being |
| // equal (for example if one represents a C++ class, and the other some class |
| // derived from it) so it would be wrong to perform this transform in general. |
| // However the transform is correct and useful if F is a subset of L. In that |
| // case L can be replaced by F, and thus removed altogether since repeating a |
| // filter is pointless. So here we look at all pairs of filters F and L where |
| // L follows F in the list of clauses, and remove L if every element of F is |
| // an element of L. This can occur when inlining C++ functions with exception |
| // specifications. |
| for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) { |
| // Examine each filter in turn. |
| Value *Filter = NewClauses[i]; |
| ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType()); |
| if (!FTy) |
| // Not a filter - skip it. |
| continue; |
| unsigned FElts = FTy->getNumElements(); |
| // Examine each filter following this one. Doing this backwards means that |
| // we don't have to worry about filters disappearing under us when removed. |
| for (unsigned j = NewClauses.size() - 1; j != i; --j) { |
| Value *LFilter = NewClauses[j]; |
| ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType()); |
| if (!LTy) |
| // Not a filter - skip it. |
| continue; |
| // If Filter is a subset of LFilter, i.e. every element of Filter is also |
| // an element of LFilter, then discard LFilter. |
| SmallVector<Value *, 16>::iterator J = NewClauses.begin() + j; |
| // If Filter is empty then it is a subset of LFilter. |
| if (!FElts) { |
| // Discard LFilter. |
| NewClauses.erase(J); |
| MakeNewInstruction = true; |
| // Move on to the next filter. |
| continue; |
| } |
| unsigned LElts = LTy->getNumElements(); |
| // If Filter is longer than LFilter then it cannot be a subset of it. |
| if (FElts > LElts) |
| // Move on to the next filter. |
| continue; |
| // At this point we know that LFilter has at least one element. |
| if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros. |
| // Filter is a subset of LFilter iff Filter contains only zeros (as we |
| // already know that Filter is not longer than LFilter). |
| if (isa<ConstantAggregateZero>(Filter)) { |
| assert(FElts <= LElts && "Should have handled this case earlier!"); |
| // Discard LFilter. |
| NewClauses.erase(J); |
| MakeNewInstruction = true; |
| } |
| // Move on to the next filter. |
| continue; |
| } |
| ConstantArray *LArray = cast<ConstantArray>(LFilter); |
| if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros. |
| // Since Filter is non-empty and contains only zeros, it is a subset of |
| // LFilter iff LFilter contains a zero. |
| assert(FElts > 0 && "Should have eliminated the empty filter earlier!"); |
| for (unsigned l = 0; l != LElts; ++l) |
| if (LArray->getOperand(l)->isNullValue()) { |
| // LFilter contains a zero - discard it. |
| NewClauses.erase(J); |
| MakeNewInstruction = true; |
| break; |
| } |
| // Move on to the next filter. |
| continue; |
| } |
| // At this point we know that both filters are ConstantArrays. Loop over |
| // operands to see whether every element of Filter is also an element of |
| // LFilter. Since filters tend to be short this is probably faster than |
| // using a method that scales nicely. |
| ConstantArray *FArray = cast<ConstantArray>(Filter); |
| bool AllFound = true; |
| for (unsigned f = 0; f != FElts; ++f) { |
| Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts(); |
| AllFound = false; |
| for (unsigned l = 0; l != LElts; ++l) { |
| Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts(); |
| if (LTypeInfo == FTypeInfo) { |
| AllFound = true; |
| break; |
| } |
| } |
| if (!AllFound) |
| break; |
| } |
| if (AllFound) { |
| // Discard LFilter. |
| NewClauses.erase(J); |
| MakeNewInstruction = true; |
| } |
| // Move on to the next filter. |
| } |
| } |
| |
| // If we changed any of the clauses, replace the old landingpad instruction |
| // with a new one. |
| if (MakeNewInstruction) { |
| LandingPadInst *NLI = LandingPadInst::Create(LI.getType(), |
| LI.getPersonalityFn(), |
| NewClauses.size()); |
| for (unsigned i = 0, e = NewClauses.size(); i != e; ++i) |
| NLI->addClause(NewClauses[i]); |
| // A landing pad with no clauses must have the cleanup flag set. It is |
| // theoretically possible, though highly unlikely, that we eliminated all |
| // clauses. If so, force the cleanup flag to true. |
| if (NewClauses.empty()) |
| CleanupFlag = true; |
| NLI->setCleanup(CleanupFlag); |
| return NLI; |
| } |
| |
| // Even if none of the clauses changed, we may nonetheless have understood |
| // that the cleanup flag is pointless. Clear it if so. |
| if (LI.isCleanup() != CleanupFlag) { |
| assert(!CleanupFlag && "Adding a cleanup, not removing one?!"); |
| LI.setCleanup(CleanupFlag); |
| return &LI; |
| } |
| |
| return 0; |
| } |
| |
| |
| |
| |
| /// TryToSinkInstruction - Try to move the specified instruction from its |
| /// current block into the beginning of DestBlock, which can only happen if it's |
| /// safe to move the instruction past all of the instructions between it and the |
| /// end of its block. |
| static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { |
| assert(I->hasOneUse() && "Invariants didn't hold!"); |
| |
| // Cannot move control-flow-involving, volatile loads, vaarg, etc. |
| if (isa<PHINode>(I) || isa<LandingPadInst>(I) || I->mayHaveSideEffects() || |
| isa<TerminatorInst>(I)) |
| return false; |
| |
| // Do not sink alloca instructions out of the entry block. |
| if (isa<AllocaInst>(I) && I->getParent() == |
| &DestBlock->getParent()->getEntryBlock()) |
| return false; |
| |
| // We can only sink load instructions if there is nothing between the load and |
| // the end of block that could change the value. |
| if (I->mayReadFromMemory()) { |
| for (BasicBlock::iterator Scan = I, E = I->getParent()->end(); |
| Scan != E; ++Scan) |
| if (Scan->mayWriteToMemory()) |
| return false; |
| } |
| |
| BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt(); |
| I->moveBefore(InsertPos); |
| ++NumSunkInst; |
| return true; |
| } |
| |
| |
| /// AddReachableCodeToWorklist - Walk the function in depth-first order, adding |
| /// all reachable code to the worklist. |
| /// |
| /// This has a couple of tricks to make the code faster and more powerful. In |
| /// particular, we constant fold and DCE instructions as we go, to avoid adding |
| /// them to the worklist (this significantly speeds up instcombine on code where |
| /// many instructions are dead or constant). Additionally, if we find a branch |
| /// whose condition is a known constant, we only visit the reachable successors. |
| /// |
| static bool AddReachableCodeToWorklist(BasicBlock *BB, |
| SmallPtrSet<BasicBlock*, 64> &Visited, |
| InstCombiner &IC, |
| const DataLayout *TD, |
| const TargetLibraryInfo *TLI) { |
| bool MadeIRChange = false; |
| SmallVector<BasicBlock*, 256> Worklist; |
| Worklist.push_back(BB); |
| |
| SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; |
| DenseMap<ConstantExpr*, Constant*> FoldedConstants; |
| |
| do { |
| BB = Worklist.pop_back_val(); |
| |
| // We have now visited this block! If we've already been here, ignore it. |
| if (!Visited.insert(BB)) continue; |
| |
| for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { |
| Instruction *Inst = BBI++; |
| |
| // DCE instruction if trivially dead. |
| if (isInstructionTriviallyDead(Inst, TLI)) { |
| ++NumDeadInst; |
| DEBUG(errs() << "IC: DCE: " << *Inst << '\n'); |
| Inst->eraseFromParent(); |
| continue; |
| } |
| |
| // ConstantProp instruction if trivially constant. |
| if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0))) |
| if (Constant *C = ConstantFoldInstruction(Inst, TD, TLI)) { |
| DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " |
| << *Inst << '\n'); |
| Inst->replaceAllUsesWith(C); |
| ++NumConstProp; |
| Inst->eraseFromParent(); |
| continue; |
| } |
| |
| if (TD) { |
| // See if we can constant fold its operands. |
| for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end(); |
| i != e; ++i) { |
| ConstantExpr *CE = dyn_cast<ConstantExpr>(i); |
| if (CE == 0) continue; |
| |
| Constant*& FoldRes = FoldedConstants[CE]; |
| if (!FoldRes) |
| FoldRes = ConstantFoldConstantExpression(CE, TD, TLI); |
| if (!FoldRes) |
| FoldRes = CE; |
| |
| if (FoldRes != CE) { |
| *i = FoldRes; |
| MadeIRChange = true; |
| } |
| } |
| } |
| |
| InstrsForInstCombineWorklist.push_back(Inst); |
| } |
| |
| // Recursively visit successors. If this is a branch or switch on a |
| // constant, only visit the reachable successor. |
| TerminatorInst *TI = BB->getTerminator(); |
| if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { |
| if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) { |
| bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue(); |
| BasicBlock *ReachableBB = BI->getSuccessor(!CondVal); |
| Worklist.push_back(ReachableBB); |
| continue; |
| } |
| } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { |
| if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) { |
| // See if this is an explicit destination. |
| for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); |
| i != e; ++i) |
| if (i.getCaseValue() == Cond) { |
| BasicBlock *ReachableBB = i.getCaseSuccessor(); |
| Worklist.push_back(ReachableBB); |
| continue; |
| } |
| |
| // Otherwise it is the default destination. |
| Worklist.push_back(SI->getDefaultDest()); |
| continue; |
| } |
| } |
| |
| for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) |
| Worklist.push_back(TI->getSuccessor(i)); |
| } while (!Worklist.empty()); |
| |
| // Once we've found all of the instructions to add to instcombine's worklist, |
| // add them in reverse order. This way instcombine will visit from the top |
| // of the function down. This jives well with the way that it adds all uses |
| // of instructions to the worklist after doing a transformation, thus avoiding |
| // some N^2 behavior in pathological cases. |
| IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0], |
| InstrsForInstCombineWorklist.size()); |
| |
| return MadeIRChange; |
| } |
| |
| bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) { |
| MadeIRChange = false; |
| |
| DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " |
| << F.getName() << "\n"); |
| |
| { |
| // Do a depth-first traversal of the function, populate the worklist with |
| // the reachable instructions. Ignore blocks that are not reachable. Keep |
| // track of which blocks we visit. |
| SmallPtrSet<BasicBlock*, 64> Visited; |
| MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, TD, |
| TLI); |
| |
| // Do a quick scan over the function. If we find any blocks that are |
| // unreachable, remove any instructions inside of them. This prevents |
| // the instcombine code from having to deal with some bad special cases. |
| for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { |
| if (Visited.count(BB)) continue; |
| |
| // Delete the instructions backwards, as it has a reduced likelihood of |
| // having to update as many def-use and use-def chains. |
| Instruction *EndInst = BB->getTerminator(); // Last not to be deleted. |
| while (EndInst != BB->begin()) { |
| // Delete the next to last instruction. |
| BasicBlock::iterator I = EndInst; |
| Instruction *Inst = --I; |
| if (!Inst->use_empty()) |
| Inst->replaceAllUsesWith(UndefValue::get(Inst->getType())); |
| if (isa<LandingPadInst>(Inst)) { |
| EndInst = Inst; |
| continue; |
| } |
| if (!isa<DbgInfoIntrinsic>(Inst)) { |
| ++NumDeadInst; |
| MadeIRChange = true; |
| } |
| Inst->eraseFromParent(); |
| } |
| } |
| } |
| |
| while (!Worklist.isEmpty()) { |
| Instruction *I = Worklist.RemoveOne(); |
| if (I == 0) continue; // skip null values. |
| |
| // Check to see if we can DCE the instruction. |
| if (isInstructionTriviallyDead(I, TLI)) { |
| DEBUG(errs() << "IC: DCE: " << *I << '\n'); |
| EraseInstFromFunction(*I); |
| ++NumDeadInst; |
| MadeIRChange = true; |
| continue; |
| } |
| |
| // Instruction isn't dead, see if we can constant propagate it. |
| if (!I->use_empty() && isa<Constant>(I->getOperand(0))) |
| if (Constant *C = ConstantFoldInstruction(I, TD, TLI)) { |
| DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n'); |
| |
| // Add operands to the worklist. |
| ReplaceInstUsesWith(*I, C); |
| ++NumConstProp; |
| EraseInstFromFunction(*I); |
| MadeIRChange = true; |
| continue; |
| } |
| |
| // See if we can trivially sink this instruction to a successor basic block. |
| if (I->hasOneUse()) { |
| BasicBlock *BB = I->getParent(); |
| Instruction *UserInst = cast<Instruction>(I->use_back()); |
| BasicBlock *UserParent; |
| |
| // Get the block the use occurs in. |
| if (PHINode *PN = dyn_cast<PHINode>(UserInst)) |
| UserParent = PN->getIncomingBlock(I->use_begin().getUse()); |
| else |
| UserParent = UserInst->getParent(); |
| |
| if (UserParent != BB) { |
| bool UserIsSuccessor = false; |
| // See if the user is one of our successors. |
| for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) |
| if (*SI == UserParent) { |
| UserIsSuccessor = true; |
| break; |
| } |
| |
| // If the user is one of our immediate successors, and if that successor |
| // only has us as a predecessors (we'd have to split the critical edge |
| // otherwise), we can keep going. |
| if (UserIsSuccessor && UserParent->getSinglePredecessor()) |
| // Okay, the CFG is simple enough, try to sink this instruction. |
| MadeIRChange |= TryToSinkInstruction(I, UserParent); |
| } |
| } |
| |
| // Now that we have an instruction, try combining it to simplify it. |
| Builder->SetInsertPoint(I->getParent(), I); |
| Builder->SetCurrentDebugLocation(I->getDebugLoc()); |
| |
| #ifndef NDEBUG |
| std::string OrigI; |
| #endif |
| DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); |
| DEBUG(errs() << "IC: Visiting: " << OrigI << '\n'); |
| |
| if (Instruction *Result = visit(*I)) { |
| ++NumCombined; |
| // Should we replace the old instruction with a new one? |
| if (Result != I) { |
| DEBUG(errs() << "IC: Old = " << *I << '\n' |
| << " New = " << *Result << '\n'); |
| |
| if (!I->getDebugLoc().isUnknown()) |
| Result->setDebugLoc(I->getDebugLoc()); |
| // Everything uses the new instruction now. |
| I->replaceAllUsesWith(Result); |
| |
| // Move the name to the new instruction first. |
| Result->takeName(I); |
| |
| // Push the new instruction and any users onto the worklist. |
| Worklist.Add(Result); |
| Worklist.AddUsersToWorkList(*Result); |
| |
| // Insert the new instruction into the basic block... |
| BasicBlock *InstParent = I->getParent(); |
| BasicBlock::iterator InsertPos = I; |
| |
| // If we replace a PHI with something that isn't a PHI, fix up the |
| // insertion point. |
| if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos)) |
| InsertPos = InstParent->getFirstInsertionPt(); |
| |
| InstParent->getInstList().insert(InsertPos, Result); |
| |
| EraseInstFromFunction(*I); |
| } else { |
| #ifndef NDEBUG |
| DEBUG(errs() << "IC: Mod = " << OrigI << '\n' |
| << " New = " << *I << '\n'); |
| #endif |
| |
| // If the instruction was modified, it's possible that it is now dead. |
| // if so, remove it. |
| if (isInstructionTriviallyDead(I, TLI)) { |
| EraseInstFromFunction(*I); |
| } else { |
| Worklist.Add(I); |
| Worklist.AddUsersToWorkList(*I); |
| } |
| } |
| MadeIRChange = true; |
| } |
| } |
| |
| Worklist.Zap(); |
| return MadeIRChange; |
| } |
| |
| namespace { |
| class InstCombinerLibCallSimplifier : public LibCallSimplifier { |
| InstCombiner *IC; |
| public: |
| InstCombinerLibCallSimplifier(const DataLayout *TD, |
| const TargetLibraryInfo *TLI, |
| InstCombiner *IC) |
| : LibCallSimplifier(TD, TLI, UnsafeFPShrink) { |
| this->IC = IC; |
| } |
| |
| /// replaceAllUsesWith - override so that instruction replacement |
| /// can be defined in terms of the instruction combiner framework. |
| virtual void replaceAllUsesWith(Instruction *I, Value *With) const { |
| IC->ReplaceInstUsesWith(*I, With); |
| } |
| }; |
| } |
| |
| bool InstCombiner::runOnFunction(Function &F) { |
| TD = getAnalysisIfAvailable<DataLayout>(); |
| TLI = &getAnalysis<TargetLibraryInfo>(); |
| |
| /// Builder - This is an IRBuilder that automatically inserts new |
| /// instructions into the worklist when they are created. |
| IRBuilder<true, TargetFolder, InstCombineIRInserter> |
| TheBuilder(F.getContext(), TargetFolder(TD), |
| InstCombineIRInserter(Worklist)); |
| Builder = &TheBuilder; |
| |
| InstCombinerLibCallSimplifier TheSimplifier(TD, TLI, this); |
| Simplifier = &TheSimplifier; |
| |
| bool EverMadeChange = false; |
| |
| // Lower dbg.declare intrinsics otherwise their value may be clobbered |
| // by instcombiner. |
| EverMadeChange = LowerDbgDeclare(F); |
| |
| // Iterate while there is work to do. |
| unsigned Iteration = 0; |
| while (DoOneIteration(F, Iteration++)) |
| EverMadeChange = true; |
| |
| Builder = 0; |
| return EverMadeChange; |
| } |
| |
| FunctionPass *llvm::createInstructionCombiningPass() { |
| return new InstCombiner(); |
| } |