lib/Target/R600/SILowerControlFlow.cpp - platform/external/llvm - Git at Google

 //===-- SILowerControlFlow.cpp - Use predicates for control flow ----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 /// \file
 /// \brief This pass lowers the pseudo control flow instructions to real
 /// machine instructions.
 ///
 /// All control flow is handled using predicated instructions and
 /// a predicate stack.  Each Scalar ALU controls the operations of 64 Vector
 /// ALUs.  The Scalar ALU can update the predicate for any of the Vector ALUs
 /// by writting to the 64-bit EXEC register (each bit corresponds to a
 /// single vector ALU).  Typically, for predicates, a vector ALU will write
 /// to its bit of the VCC register (like EXEC VCC is 64-bits, one for each
 /// Vector ALU) and then the ScalarALU will AND the VCC register with the
 /// EXEC to update the predicates.
 ///
 /// For example:
 /// %VCC = V_CMP_GT_F32 %VGPR1, %VGPR2
 /// %SGPR0 = SI_IF %VCC
 ///   %VGPR0 = V_ADD_F32 %VGPR0, %VGPR0
 /// %SGPR0 = SI_ELSE %SGPR0
 ///   %VGPR0 = V_SUB_F32 %VGPR0, %VGPR0
 /// SI_END_CF %SGPR0
 ///
 /// becomes:
 ///
 /// %SGPR0 = S_AND_SAVEEXEC_B64 %VCC  // Save and update the exec mask
 /// %SGPR0 = S_XOR_B64 %SGPR0, %EXEC  // Clear live bits from saved exec mask
 /// S_CBRANCH_EXECZ label0            // This instruction is an optional
 ///                                   // optimization which allows us to
 ///                                   // branch if all the bits of
 ///                                   // EXEC are zero.
 /// %VGPR0 = V_ADD_F32 %VGPR0, %VGPR0 // Do the IF block of the branch
 ///
 /// label0:
 /// %SGPR0 = S_OR_SAVEEXEC_B64 %EXEC   // Restore the exec mask for the Then block
 /// %EXEC = S_XOR_B64 %SGPR0, %EXEC    // Clear live bits from saved exec mask
 /// S_BRANCH_EXECZ label1              // Use our branch optimization
 ///                                    // instruction again.
 /// %VGPR0 = V_SUB_F32 %VGPR0, %VGPR   // Do the THEN block
 /// label1:
 /// %EXEC = S_OR_B64 %EXEC, %SGPR0     // Re-enable saved exec mask bits
 //===----------------------------------------------------------------------===//

 #include "AMDGPU.h"
 #include "SIInstrInfo.h"
 #include "SIMachineFunctionInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"

 using namespace llvm;

 namespace {

 class SILowerControlFlowPass : public MachineFunctionPass {

 private:
   static const unsigned SkipThreshold = 12;

   static char ID;
   const TargetRegisterInfo *TRI;
   const TargetInstrInfo *TII;

   bool shouldSkip(MachineBasicBlock *From, MachineBasicBlock *To);

   void Skip(MachineInstr &From, MachineOperand &To);
   void SkipIfDead(MachineInstr &MI);

   void If(MachineInstr &MI);
   void Else(MachineInstr &MI);
   void Break(MachineInstr &MI);
   void IfBreak(MachineInstr &MI);
   void ElseBreak(MachineInstr &MI);
   void Loop(MachineInstr &MI);
   void EndCf(MachineInstr &MI);

   void Kill(MachineInstr &MI);
   void Branch(MachineInstr &MI);

   void LoadM0(MachineInstr &MI, MachineInstr *MovRel);
   void IndirectSrc(MachineInstr &MI);
   void IndirectDst(MachineInstr &MI);

 public:
   SILowerControlFlowPass(TargetMachine &tm) :
     MachineFunctionPass(ID), TRI(tm.getRegisterInfo()),
     TII(tm.getInstrInfo()) { }

   virtual bool runOnMachineFunction(MachineFunction &MF);

   const char *getPassName() const {
     return "SI Lower control flow instructions";
   }

 };

 } // End anonymous namespace

 char SILowerControlFlowPass::ID = 0;

 FunctionPass *llvm::createSILowerControlFlowPass(TargetMachine &tm) {
   return new SILowerControlFlowPass(tm);
 }

 bool SILowerControlFlowPass::shouldSkip(MachineBasicBlock *From,
                                         MachineBasicBlock *To) {

   unsigned NumInstr = 0;

   for (MachineBasicBlock *MBB = From; MBB != To && !MBB->succ_empty();
        MBB = *MBB->succ_begin()) {

     for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
          NumInstr < SkipThreshold && I != E; ++I) {

       if (I->isBundle() || !I->isBundled())
         if (++NumInstr >= SkipThreshold)
           return true;
     }
   }

   return false;
 }

 void SILowerControlFlowPass::Skip(MachineInstr &From, MachineOperand &To) {

   if (!shouldSkip(*From.getParent()->succ_begin(), To.getMBB()))
     return;

   DebugLoc DL = From.getDebugLoc();
   BuildMI(*From.getParent(), &From, DL, TII->get(AMDGPU::S_CBRANCH_EXECZ))
           .addOperand(To)
           .addReg(AMDGPU::EXEC);
 }

 void SILowerControlFlowPass::SkipIfDead(MachineInstr &MI) {

   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   if (!shouldSkip(&MBB, &MBB.getParent()->back()))
     return;

   MachineBasicBlock::iterator Insert = &MI;
   ++Insert;

   // If the exec mask is non-zero, skip the next two instructions
   BuildMI(MBB, Insert, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
           .addImm(3)
           .addReg(AMDGPU::EXEC);

   // Exec mask is zero: Export to NULL target...
   BuildMI(MBB, Insert, DL, TII->get(AMDGPU::EXP))
           .addImm(0)
           .addImm(0x09) // V_008DFC_SQ_EXP_NULL
           .addImm(0)
           .addImm(1)
           .addImm(1)
           .addReg(AMDGPU::VGPR0)
           .addReg(AMDGPU::VGPR0)
           .addReg(AMDGPU::VGPR0)
           .addReg(AMDGPU::VGPR0);

   // ... and terminate wavefront
   BuildMI(MBB, Insert, DL, TII->get(AMDGPU::S_ENDPGM));
 }

 void SILowerControlFlowPass::If(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();
   unsigned Reg = MI.getOperand(0).getReg();
   unsigned Vcc = MI.getOperand(1).getReg();

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_AND_SAVEEXEC_B64), Reg)
           .addReg(Vcc);

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), Reg)
           .addReg(AMDGPU::EXEC)
           .addReg(Reg);

   Skip(MI, MI.getOperand(2));

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::Else(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();
   unsigned Dst = MI.getOperand(0).getReg();
   unsigned Src = MI.getOperand(1).getReg();

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_SAVEEXEC_B64), Dst)
           .addReg(Src); // Saved EXEC

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), AMDGPU::EXEC)
           .addReg(AMDGPU::EXEC)
           .addReg(Dst);

   Skip(MI, MI.getOperand(2));

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::Break(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   unsigned Dst = MI.getOperand(0).getReg();
   unsigned Src = MI.getOperand(1).getReg();

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
           .addReg(AMDGPU::EXEC)
           .addReg(Src);

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::IfBreak(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   unsigned Dst = MI.getOperand(0).getReg();
   unsigned Vcc = MI.getOperand(1).getReg();
   unsigned Src = MI.getOperand(2).getReg();

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
           .addReg(Vcc)
           .addReg(Src);

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::ElseBreak(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   unsigned Dst = MI.getOperand(0).getReg();
   unsigned Saved = MI.getOperand(1).getReg();
   unsigned Src = MI.getOperand(2).getReg();

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
           .addReg(Saved)
           .addReg(Src);

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::Loop(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();
   unsigned Src = MI.getOperand(0).getReg();

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_ANDN2_B64), AMDGPU::EXEC)
           .addReg(AMDGPU::EXEC)
           .addReg(Src);

   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
           .addOperand(MI.getOperand(1))
           .addReg(AMDGPU::EXEC);

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::EndCf(MachineInstr &MI) {
   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();
   unsigned Reg = MI.getOperand(0).getReg();

   BuildMI(MBB, MBB.getFirstNonPHI(), DL,
           TII->get(AMDGPU::S_OR_B64), AMDGPU::EXEC)
           .addReg(AMDGPU::EXEC)
           .addReg(Reg);

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::Branch(MachineInstr &MI) {
   MachineBasicBlock *Next = MI.getParent()->getNextNode();
   MachineBasicBlock *Target = MI.getOperand(0).getMBB();
   if (Target == Next)
     MI.eraseFromParent();
   else
     assert(0);
 }

 void SILowerControlFlowPass::Kill(MachineInstr &MI) {

   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   // Kill is only allowed in pixel shaders
   assert(MBB.getParent()->getInfo<SIMachineFunctionInfo>()->ShaderType ==
          ShaderType::PIXEL);

   // Clear this pixel from the exec mask if the operand is negative
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMPX_LE_F32_e32), AMDGPU::VCC)
           .addImm(0)
           .addOperand(MI.getOperand(0));

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::LoadM0(MachineInstr &MI, MachineInstr *MovRel) {

   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();
   MachineBasicBlock::iterator I = MI;

   unsigned Save = MI.getOperand(1).getReg();
   unsigned Idx = MI.getOperand(3).getReg();

   if (AMDGPU::SReg_32RegClass.contains(Idx)) {
     BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::M0)
             .addReg(Idx);
     MBB.insert(I, MovRel);
     MI.eraseFromParent();
     return;
   }

   assert(AMDGPU::SReg_64RegClass.contains(Save));
   assert(AMDGPU::VReg_32RegClass.contains(Idx));

   // Save the EXEC mask
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), Save)
           .addReg(AMDGPU::EXEC);

   // Read the next variant into VCC (lower 32 bits) <- also loop target
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32_e32), AMDGPU::VCC)
           .addReg(Idx);

   // Move index from VCC into M0
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::M0)
           .addReg(AMDGPU::VCC);

   // Compare the just read M0 value to all possible Idx values
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMP_EQ_U32_e32), AMDGPU::VCC)
           .addReg(AMDGPU::M0)
           .addReg(Idx);

   // Update EXEC, save the original EXEC value to VCC
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_AND_SAVEEXEC_B64), AMDGPU::VCC)
           .addReg(AMDGPU::VCC);

   // Do the actual move
   MBB.insert(I, MovRel);

   // Update EXEC, switch all done bits to 0 and all todo bits to 1
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), AMDGPU::EXEC)
           .addReg(AMDGPU::EXEC)
           .addReg(AMDGPU::VCC);

   // Loop back to V_READFIRSTLANE_B32 if there are still variants to cover
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
           .addImm(-7)
           .addReg(AMDGPU::EXEC);

   // Restore EXEC
   BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), AMDGPU::EXEC)
           .addReg(Save);

   MI.eraseFromParent();
 }

 void SILowerControlFlowPass::IndirectSrc(MachineInstr &MI) {

   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   unsigned Dst = MI.getOperand(0).getReg();
   unsigned Vec = MI.getOperand(2).getReg();
   unsigned Off = MI.getOperand(4).getImm();

   MachineInstr *MovRel =
     BuildMI(*MBB.getParent(), DL, TII->get(AMDGPU::V_MOVRELS_B32_e32), Dst)
             .addReg(TRI->getSubReg(Vec, AMDGPU::sub0) + Off)
             .addReg(AMDGPU::M0, RegState::Implicit)
             .addReg(Vec, RegState::Implicit);

   LoadM0(MI, MovRel);
 }

 void SILowerControlFlowPass::IndirectDst(MachineInstr &MI) {

   MachineBasicBlock &MBB = *MI.getParent();
   DebugLoc DL = MI.getDebugLoc();

   unsigned Dst = MI.getOperand(0).getReg();
   unsigned Off = MI.getOperand(4).getImm();
   unsigned Val = MI.getOperand(5).getReg();

   MachineInstr *MovRel =
     BuildMI(*MBB.getParent(), DL, TII->get(AMDGPU::V_MOVRELD_B32_e32))
             .addReg(TRI->getSubReg(Dst, AMDGPU::sub0) + Off, RegState::Define)
             .addReg(Val)
             .addReg(AMDGPU::M0, RegState::Implicit)
             .addReg(Dst, RegState::Implicit);

   LoadM0(MI, MovRel);
 }

 bool SILowerControlFlowPass::runOnMachineFunction(MachineFunction &MF) {

   bool HaveKill = false;
   unsigned Depth = 0;

   for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
        BI != BE; ++BI) {

     MachineBasicBlock &MBB = *BI;
     for (MachineBasicBlock::iterator I = MBB.begin(), Next = llvm::next(I);
          I != MBB.end(); I = Next) {

       Next = llvm::next(I);
       MachineInstr &MI = *I;
       switch (MI.getOpcode()) {
         default: break;
         case AMDGPU::SI_IF:
           ++Depth;
           If(MI);
           break;

         case AMDGPU::SI_ELSE:
           Else(MI);
           break;

         case AMDGPU::SI_BREAK:
           Break(MI);
           break;

         case AMDGPU::SI_IF_BREAK:
           IfBreak(MI);
           break;

         case AMDGPU::SI_ELSE_BREAK:
           ElseBreak(MI);
           break;

         case AMDGPU::SI_LOOP:
           ++Depth;
           Loop(MI);
           break;

         case AMDGPU::SI_END_CF:
           if (--Depth == 0 && HaveKill) {
             SkipIfDead(MI);
             HaveKill = false;
           }
           EndCf(MI);
           break;

         case AMDGPU::SI_KILL:
           if (Depth == 0)
             SkipIfDead(MI);
           else
             HaveKill = true;
           Kill(MI);
           break;

         case AMDGPU::S_BRANCH:
           Branch(MI);
           break;

         case AMDGPU::SI_INDIRECT_SRC:
           IndirectSrc(MI);
           break;

         case AMDGPU::SI_INDIRECT_DST_V2:
         case AMDGPU::SI_INDIRECT_DST_V4:
         case AMDGPU::SI_INDIRECT_DST_V8:
         case AMDGPU::SI_INDIRECT_DST_V16:
           IndirectDst(MI);
           break;
       }
     }
   }

   return true;
 }
	//===-- SILowerControlFlow.cpp - Use predicates for control flow ----------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	/// \file
	/// \brief This pass lowers the pseudo control flow instructions to real
	/// machine instructions.
	///
	/// All control flow is handled using predicated instructions and
	/// a predicate stack. Each Scalar ALU controls the operations of 64 Vector
	/// ALUs. The Scalar ALU can update the predicate for any of the Vector ALUs
	/// by writting to the 64-bit EXEC register (each bit corresponds to a
	/// single vector ALU). Typically, for predicates, a vector ALU will write
	/// to its bit of the VCC register (like EXEC VCC is 64-bits, one for each
	/// Vector ALU) and then the ScalarALU will AND the VCC register with the
	/// EXEC to update the predicates.
	///
	/// For example:
	/// %VCC = V_CMP_GT_F32 %VGPR1, %VGPR2
	/// %SGPR0 = SI_IF %VCC
	/// %VGPR0 = V_ADD_F32 %VGPR0, %VGPR0
	/// %SGPR0 = SI_ELSE %SGPR0
	/// %VGPR0 = V_SUB_F32 %VGPR0, %VGPR0
	/// SI_END_CF %SGPR0
	///
	/// becomes:
	///
	/// %SGPR0 = S_AND_SAVEEXEC_B64 %VCC // Save and update the exec mask
	/// %SGPR0 = S_XOR_B64 %SGPR0, %EXEC // Clear live bits from saved exec mask
	/// S_CBRANCH_EXECZ label0 // This instruction is an optional
	/// // optimization which allows us to
	/// // branch if all the bits of
	/// // EXEC are zero.
	/// %VGPR0 = V_ADD_F32 %VGPR0, %VGPR0 // Do the IF block of the branch
	///
	/// label0:
	/// %SGPR0 = S_OR_SAVEEXEC_B64 %EXEC // Restore the exec mask for the Then block
	/// %EXEC = S_XOR_B64 %SGPR0, %EXEC // Clear live bits from saved exec mask
	/// S_BRANCH_EXECZ label1 // Use our branch optimization
	/// // instruction again.
	/// %VGPR0 = V_SUB_F32 %VGPR0, %VGPR // Do the THEN block
	/// label1:
	/// %EXEC = S_OR_B64 %EXEC, %SGPR0 // Re-enable saved exec mask bits
	//===----------------------------------------------------------------------===//

	#include "AMDGPU.h"
	#include "SIInstrInfo.h"
	#include "SIMachineFunctionInfo.h"
	#include "llvm/CodeGen/MachineFunction.h"
	#include "llvm/CodeGen/MachineFunctionPass.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	#include "llvm/CodeGen/MachineRegisterInfo.h"

	using namespace llvm;

	namespace {

	class SILowerControlFlowPass : public MachineFunctionPass {

	private:
	static const unsigned SkipThreshold = 12;

	static char ID;
	const TargetRegisterInfo *TRI;
	const TargetInstrInfo *TII;

	bool shouldSkip(MachineBasicBlock From, MachineBasicBlock To);

	void Skip(MachineInstr &From, MachineOperand &To);
	void SkipIfDead(MachineInstr &MI);

	void If(MachineInstr &MI);
	void Else(MachineInstr &MI);
	void Break(MachineInstr &MI);
	void IfBreak(MachineInstr &MI);
	void ElseBreak(MachineInstr &MI);
	void Loop(MachineInstr &MI);
	void EndCf(MachineInstr &MI);

	void Kill(MachineInstr &MI);
	void Branch(MachineInstr &MI);

	void LoadM0(MachineInstr &MI, MachineInstr *MovRel);
	void IndirectSrc(MachineInstr &MI);
	void IndirectDst(MachineInstr &MI);

	public:
	SILowerControlFlowPass(TargetMachine &tm) :
	MachineFunctionPass(ID), TRI(tm.getRegisterInfo()),
	TII(tm.getInstrInfo()) { }

	virtual bool runOnMachineFunction(MachineFunction &MF);

	const char *getPassName() const {
	return "SI Lower control flow instructions";
	}

	};

	} // End anonymous namespace

	char SILowerControlFlowPass::ID = 0;

	FunctionPass *llvm::createSILowerControlFlowPass(TargetMachine &tm) {
	return new SILowerControlFlowPass(tm);
	}

	bool SILowerControlFlowPass::shouldSkip(MachineBasicBlock *From,
	MachineBasicBlock *To) {

	unsigned NumInstr = 0;

	for (MachineBasicBlock *MBB = From; MBB != To && !MBB->succ_empty();
	MBB = *MBB->succ_begin()) {

	for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
	NumInstr < SkipThreshold && I != E; ++I) {

	if (I->isBundle() \|\| !I->isBundled())
	if (++NumInstr >= SkipThreshold)
	return true;
	}
	}

	return false;
	}

	void SILowerControlFlowPass::Skip(MachineInstr &From, MachineOperand &To) {

	if (!shouldSkip(*From.getParent()->succ_begin(), To.getMBB()))
	return;

	DebugLoc DL = From.getDebugLoc();
	BuildMI(*From.getParent(), &From, DL, TII->get(AMDGPU::S_CBRANCH_EXECZ))
	.addOperand(To)
	.addReg(AMDGPU::EXEC);
	}

	void SILowerControlFlowPass::SkipIfDead(MachineInstr &MI) {

	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	if (!shouldSkip(&MBB, &MBB.getParent()->back()))
	return;

	MachineBasicBlock::iterator Insert = &MI;
	++Insert;

	// If the exec mask is non-zero, skip the next two instructions
	BuildMI(MBB, Insert, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
	.addImm(3)
	.addReg(AMDGPU::EXEC);

	// Exec mask is zero: Export to NULL target...
	BuildMI(MBB, Insert, DL, TII->get(AMDGPU::EXP))
	.addImm(0)
	.addImm(0x09) // V_008DFC_SQ_EXP_NULL
	.addImm(0)
	.addImm(1)
	.addImm(1)
	.addReg(AMDGPU::VGPR0)
	.addReg(AMDGPU::VGPR0)
	.addReg(AMDGPU::VGPR0)
	.addReg(AMDGPU::VGPR0);

	// ... and terminate wavefront
	BuildMI(MBB, Insert, DL, TII->get(AMDGPU::S_ENDPGM));
	}

	void SILowerControlFlowPass::If(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();
	unsigned Reg = MI.getOperand(0).getReg();
	unsigned Vcc = MI.getOperand(1).getReg();

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_AND_SAVEEXEC_B64), Reg)
	.addReg(Vcc);

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), Reg)
	.addReg(AMDGPU::EXEC)
	.addReg(Reg);

	Skip(MI, MI.getOperand(2));

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::Else(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();
	unsigned Dst = MI.getOperand(0).getReg();
	unsigned Src = MI.getOperand(1).getReg();

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_SAVEEXEC_B64), Dst)
	.addReg(Src); // Saved EXEC

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), AMDGPU::EXEC)
	.addReg(AMDGPU::EXEC)
	.addReg(Dst);

	Skip(MI, MI.getOperand(2));

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::Break(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	unsigned Dst = MI.getOperand(0).getReg();
	unsigned Src = MI.getOperand(1).getReg();

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
	.addReg(AMDGPU::EXEC)
	.addReg(Src);

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::IfBreak(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	unsigned Dst = MI.getOperand(0).getReg();
	unsigned Vcc = MI.getOperand(1).getReg();
	unsigned Src = MI.getOperand(2).getReg();

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
	.addReg(Vcc)
	.addReg(Src);

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::ElseBreak(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	unsigned Dst = MI.getOperand(0).getReg();
	unsigned Saved = MI.getOperand(1).getReg();
	unsigned Src = MI.getOperand(2).getReg();

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_OR_B64), Dst)
	.addReg(Saved)
	.addReg(Src);

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::Loop(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();
	unsigned Src = MI.getOperand(0).getReg();

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_ANDN2_B64), AMDGPU::EXEC)
	.addReg(AMDGPU::EXEC)
	.addReg(Src);

	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
	.addOperand(MI.getOperand(1))
	.addReg(AMDGPU::EXEC);

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::EndCf(MachineInstr &MI) {
	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();
	unsigned Reg = MI.getOperand(0).getReg();

	BuildMI(MBB, MBB.getFirstNonPHI(), DL,
	TII->get(AMDGPU::S_OR_B64), AMDGPU::EXEC)
	.addReg(AMDGPU::EXEC)
	.addReg(Reg);

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::Branch(MachineInstr &MI) {
	MachineBasicBlock *Next = MI.getParent()->getNextNode();
	MachineBasicBlock *Target = MI.getOperand(0).getMBB();
	if (Target == Next)
	MI.eraseFromParent();
	else
	assert(0);
	}

	void SILowerControlFlowPass::Kill(MachineInstr &MI) {

	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	// Kill is only allowed in pixel shaders
	assert(MBB.getParent()->getInfo<SIMachineFunctionInfo>()->ShaderType ==
	ShaderType::PIXEL);

	// Clear this pixel from the exec mask if the operand is negative
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMPX_LE_F32_e32), AMDGPU::VCC)
	.addImm(0)
	.addOperand(MI.getOperand(0));

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::LoadM0(MachineInstr &MI, MachineInstr *MovRel) {

	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();
	MachineBasicBlock::iterator I = MI;

	unsigned Save = MI.getOperand(1).getReg();
	unsigned Idx = MI.getOperand(3).getReg();

	if (AMDGPU::SReg_32RegClass.contains(Idx)) {
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::M0)
	.addReg(Idx);
	MBB.insert(I, MovRel);
	MI.eraseFromParent();
	return;
	}

	assert(AMDGPU::SReg_64RegClass.contains(Save));
	assert(AMDGPU::VReg_32RegClass.contains(Idx));

	// Save the EXEC mask
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), Save)
	.addReg(AMDGPU::EXEC);

	// Read the next variant into VCC (lower 32 bits) <- also loop target
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32_e32), AMDGPU::VCC)
	.addReg(Idx);

	// Move index from VCC into M0
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B32), AMDGPU::M0)
	.addReg(AMDGPU::VCC);

	// Compare the just read M0 value to all possible Idx values
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMP_EQ_U32_e32), AMDGPU::VCC)
	.addReg(AMDGPU::M0)
	.addReg(Idx);

	// Update EXEC, save the original EXEC value to VCC
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_AND_SAVEEXEC_B64), AMDGPU::VCC)
	.addReg(AMDGPU::VCC);

	// Do the actual move
	MBB.insert(I, MovRel);

	// Update EXEC, switch all done bits to 0 and all todo bits to 1
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_XOR_B64), AMDGPU::EXEC)
	.addReg(AMDGPU::EXEC)
	.addReg(AMDGPU::VCC);

	// Loop back to V_READFIRSTLANE_B32 if there are still variants to cover
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_CBRANCH_EXECNZ))
	.addImm(-7)
	.addReg(AMDGPU::EXEC);

	// Restore EXEC
	BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), AMDGPU::EXEC)
	.addReg(Save);

	MI.eraseFromParent();
	}

	void SILowerControlFlowPass::IndirectSrc(MachineInstr &MI) {

	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	unsigned Dst = MI.getOperand(0).getReg();
	unsigned Vec = MI.getOperand(2).getReg();
	unsigned Off = MI.getOperand(4).getImm();

	MachineInstr *MovRel =
	BuildMI(*MBB.getParent(), DL, TII->get(AMDGPU::V_MOVRELS_B32_e32), Dst)
	.addReg(TRI->getSubReg(Vec, AMDGPU::sub0) + Off)
	.addReg(AMDGPU::M0, RegState::Implicit)
	.addReg(Vec, RegState::Implicit);

	LoadM0(MI, MovRel);
	}

	void SILowerControlFlowPass::IndirectDst(MachineInstr &MI) {

	MachineBasicBlock &MBB = *MI.getParent();
	DebugLoc DL = MI.getDebugLoc();

	unsigned Dst = MI.getOperand(0).getReg();
	unsigned Off = MI.getOperand(4).getImm();
	unsigned Val = MI.getOperand(5).getReg();

	MachineInstr *MovRel =
	BuildMI(*MBB.getParent(), DL, TII->get(AMDGPU::V_MOVRELD_B32_e32))
	.addReg(TRI->getSubReg(Dst, AMDGPU::sub0) + Off, RegState::Define)
	.addReg(Val)
	.addReg(AMDGPU::M0, RegState::Implicit)
	.addReg(Dst, RegState::Implicit);

	LoadM0(MI, MovRel);
	}

	bool SILowerControlFlowPass::runOnMachineFunction(MachineFunction &MF) {

	bool HaveKill = false;
	unsigned Depth = 0;

	for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
	BI != BE; ++BI) {

	MachineBasicBlock &MBB = *BI;
	for (MachineBasicBlock::iterator I = MBB.begin(), Next = llvm::next(I);
	I != MBB.end(); I = Next) {

	Next = llvm::next(I);
	MachineInstr &MI = *I;
	switch (MI.getOpcode()) {
	default: break;
	case AMDGPU::SI_IF:
	++Depth;
	If(MI);
	break;

	case AMDGPU::SI_ELSE:
	Else(MI);
	break;

	case AMDGPU::SI_BREAK:
	Break(MI);
	break;

	case AMDGPU::SI_IF_BREAK:
	IfBreak(MI);
	break;

	case AMDGPU::SI_ELSE_BREAK:
	ElseBreak(MI);
	break;

	case AMDGPU::SI_LOOP:
	++Depth;
	Loop(MI);
	break;

	case AMDGPU::SI_END_CF:
	if (--Depth == 0 && HaveKill) {
	SkipIfDead(MI);
	HaveKill = false;
	}
	EndCf(MI);
	break;

	case AMDGPU::SI_KILL:
	if (Depth == 0)
	SkipIfDead(MI);
	else
	HaveKill = true;
	Kill(MI);
	break;

	case AMDGPU::S_BRANCH:
	Branch(MI);
	break;

	case AMDGPU::SI_INDIRECT_SRC:
	IndirectSrc(MI);
	break;

	case AMDGPU::SI_INDIRECT_DST_V2:
	case AMDGPU::SI_INDIRECT_DST_V4:
	case AMDGPU::SI_INDIRECT_DST_V8:
	case AMDGPU::SI_INDIRECT_DST_V16:
	IndirectDst(MI);
	break;
	}
	}
	}

	return true;
	}