test/Transforms/SROA/phi-and-select.ll - platform/external/llvm - Git at Google

 ; RUN: opt < %s -sroa -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n8:16:32:64"

 define i32 @test1() {
 ; CHECK: @test1
 entry:
 	%a = alloca [2 x i32]
 ; CHECK-NOT: alloca

   %a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
   %a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
 	store i32 0, i32* %a0
 	store i32 1, i32* %a1
 	%v0 = load i32* %a0
 	%v1 = load i32* %a1
 ; CHECK-NOT: store
 ; CHECK-NOT: load

 	%cond = icmp sle i32 %v0, %v1
 	br i1 %cond, label %then, label %exit

 then:
 	br label %exit

 exit:
 	%phi = phi i32* [ %a1, %then ], [ %a0, %entry ]
 ; CHECK: phi i32 [ 1, %{{.*}} ], [ 0, %{{.*}} ]

 	%result = load i32* %phi
 	ret i32 %result
 }

 define i32 @test2() {
 ; CHECK: @test2
 entry:
 	%a = alloca [2 x i32]
 ; CHECK-NOT: alloca

   %a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
   %a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
 	store i32 0, i32* %a0
 	store i32 1, i32* %a1
 	%v0 = load i32* %a0
 	%v1 = load i32* %a1
 ; CHECK-NOT: store
 ; CHECK-NOT: load

 	%cond = icmp sle i32 %v0, %v1
 	%select = select i1 %cond, i32* %a1, i32* %a0
 ; CHECK: select i1 %{{.*}}, i32 1, i32 0

 	%result = load i32* %select
 	ret i32 %result
 }

 define i32 @test3(i32 %x) {
 ; CHECK: @test3
 entry:
 	%a = alloca [2 x i32]
 ; CHECK-NOT: alloca

   ; Note that we build redundant GEPs here to ensure that having different GEPs
   ; into the same alloca partation continues to work with PHI speculation. This
   ; was the underlying cause of PR13926.
   %a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
   %a0b = getelementptr [2 x i32]* %a, i64 0, i32 0
   %a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
   %a1b = getelementptr [2 x i32]* %a, i64 0, i32 1
 	store i32 0, i32* %a0
 	store i32 1, i32* %a1
 ; CHECK-NOT: store

   switch i32 %x, label %bb0 [ i32 1, label %bb1
                               i32 2, label %bb2
                               i32 3, label %bb3
                               i32 4, label %bb4
                               i32 5, label %bb5
                               i32 6, label %bb6
                               i32 7, label %bb7 ]

 bb0:
 	br label %exit
 bb1:
 	br label %exit
 bb2:
 	br label %exit
 bb3:
 	br label %exit
 bb4:
 	br label %exit
 bb5:
 	br label %exit
 bb6:
 	br label %exit
 bb7:
 	br label %exit

 exit:
 	%phi = phi i32* [ %a1, %bb0 ], [ %a0, %bb1 ], [ %a0, %bb2 ], [ %a1, %bb3 ],
                   [ %a1b, %bb4 ], [ %a0b, %bb5 ], [ %a0b, %bb6 ], [ %a1b, %bb7 ]
 ; CHECK: phi i32 [ 1, %{{.*}} ], [ 0, %{{.*}} ], [ 0, %{{.*}} ], [ 1, %{{.*}} ], [ 1, %{{.*}} ], [ 0, %{{.*}} ], [ 0, %{{.*}} ], [ 1, %{{.*}} ]

 	%result = load i32* %phi
 	ret i32 %result
 }

 define i32 @test4() {
 ; CHECK: @test4
 entry:
 	%a = alloca [2 x i32]
 ; CHECK-NOT: alloca

   %a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
   %a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
 	store i32 0, i32* %a0
 	store i32 1, i32* %a1
 	%v0 = load i32* %a0
 	%v1 = load i32* %a1
 ; CHECK-NOT: store
 ; CHECK-NOT: load

 	%cond = icmp sle i32 %v0, %v1
 	%select = select i1 %cond, i32* %a0, i32* %a0
 ; CHECK-NOT: select

 	%result = load i32* %select
 	ret i32 %result
 ; CHECK: ret i32 0
 }

 define i32 @test5(i32* %b) {
 ; CHECK: @test5
 entry:
 	%a = alloca [2 x i32]
 ; CHECK-NOT: alloca

   %a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
 	store i32 1, i32* %a1
 ; CHECK-NOT: store

 	%select = select i1 true, i32* %a1, i32* %b
 ; CHECK-NOT: select

 	%result = load i32* %select
 ; CHECK-NOT: load

 	ret i32 %result
 ; CHECK: ret i32 1
 }

 declare void @f(i32*, i32*)

 define i32 @test6(i32* %b) {
 ; CHECK: @test6
 entry:
 	%a = alloca [2 x i32]
   %c = alloca i32
 ; CHECK-NOT: alloca

   %a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
 	store i32 1, i32* %a1

 	%select = select i1 true, i32* %a1, i32* %b
 	%select2 = select i1 false, i32* %a1, i32* %b
   %select3 = select i1 false, i32* %c, i32* %b
 ; CHECK: %[[select2:.*]] = select i1 false, i32* undef, i32* %b
 ; CHECK: %[[select3:.*]] = select i1 false, i32* undef, i32* %b

   ; Note, this would potentially escape the alloca pointer except for the
   ; constant folding of the select.
   call void @f(i32* %select2, i32* %select3)
 ; CHECK: call void @f(i32* %[[select2]], i32* %[[select3]])


 	%result = load i32* %select
 ; CHECK-NOT: load

   %dead = load i32* %c

 	ret i32 %result
 ; CHECK: ret i32 1
 }

 define i32 @test7() {
 ; CHECK: @test7
 ; CHECK-NOT: alloca

 entry:
   %X = alloca i32
   br i1 undef, label %good, label %bad

 good:
   %Y1 = getelementptr i32* %X, i64 0
   store i32 0, i32* %Y1
   br label %exit

 bad:
   %Y2 = getelementptr i32* %X, i64 1
   store i32 0, i32* %Y2
   br label %exit

 exit:
 	%P = phi i32* [ %Y1, %good ], [ %Y2, %bad ]
 ; CHECK: %[[phi:.*]] = phi i32 [ 0, %good ],
   %Z2 = load i32* %P
   ret i32 %Z2
 ; CHECK: ret i32 %[[phi]]
 }

 define i32 @test8(i32 %b, i32* %ptr) {
 ; Ensure that we rewrite allocas to the used type when that use is hidden by
 ; a PHI that can be speculated.
 ; CHECK: @test8
 ; CHECK-NOT: alloca
 ; CHECK-NOT: load
 ; CHECK: %[[value:.*]] = load i32* %ptr
 ; CHECK-NOT: load
 ; CHECK: %[[result:.*]] = phi i32 [ undef, %else ], [ %[[value]], %then ]
 ; CHECK-NEXT: ret i32 %[[result]]

 entry:
   %f = alloca float
   %test = icmp ne i32 %b, 0
   br i1 %test, label %then, label %else

 then:
   br label %exit

 else:
   %bitcast = bitcast float* %f to i32*
   br label %exit

 exit:
   %phi = phi i32* [ %bitcast, %else ], [ %ptr, %then ]
   %loaded = load i32* %phi, align 4
   ret i32 %loaded
 }

 define i32 @test9(i32 %b, i32* %ptr) {
 ; Same as @test8 but for a select rather than a PHI node.
 ; CHECK: @test9
 ; CHECK-NOT: alloca
 ; CHECK-NOT: load
 ; CHECK: %[[value:.*]] = load i32* %ptr
 ; CHECK-NOT: load
 ; CHECK: %[[result:.*]] = select i1 %{{.*}}, i32 undef, i32 %[[value]]
 ; CHECK-NEXT: ret i32 %[[result]]

 entry:
   %f = alloca float
   store i32 0, i32* %ptr
   %test = icmp ne i32 %b, 0
   %bitcast = bitcast float* %f to i32*
   %select = select i1 %test, i32* %bitcast, i32* %ptr
   %loaded = load i32* %select, align 4
   ret i32 %loaded
 }

 define float @test10(i32 %b, float* %ptr) {
 ; Don't try to promote allocas which are not elligible for it even after
 ; rewriting due to the necessity of inserting bitcasts when speculating a PHI
 ; node.
 ; CHECK: @test10
 ; CHECK: %[[alloca:.*]] = alloca
 ; CHECK: %[[argvalue:.*]] = load float* %ptr
 ; CHECK: %[[cast:.*]] = bitcast double* %[[alloca]] to float*
 ; CHECK: %[[allocavalue:.*]] = load float* %[[cast]]
 ; CHECK: %[[result:.*]] = phi float [ %[[allocavalue]], %else ], [ %[[argvalue]], %then ]
 ; CHECK-NEXT: ret float %[[result]]

 entry:
   %f = alloca double
   store double 0.0, double* %f
   %test = icmp ne i32 %b, 0
   br i1 %test, label %then, label %else

 then:
   br label %exit

 else:
   %bitcast = bitcast double* %f to float*
   br label %exit

 exit:
   %phi = phi float* [ %bitcast, %else ], [ %ptr, %then ]
   %loaded = load float* %phi, align 4
   ret float %loaded
 }

 define float @test11(i32 %b, float* %ptr) {
 ; Same as @test10 but for a select rather than a PHI node.
 ; CHECK: @test11
 ; CHECK: %[[alloca:.*]] = alloca
 ; CHECK: %[[cast:.*]] = bitcast double* %[[alloca]] to float*
 ; CHECK: %[[allocavalue:.*]] = load float* %[[cast]]
 ; CHECK: %[[argvalue:.*]] = load float* %ptr
 ; CHECK: %[[result:.*]] = select i1 %{{.*}}, float %[[allocavalue]], float %[[argvalue]]
 ; CHECK-NEXT: ret float %[[result]]

 entry:
   %f = alloca double
   store double 0.0, double* %f
   store float 0.0, float* %ptr
   %test = icmp ne i32 %b, 0
   %bitcast = bitcast double* %f to float*
   %select = select i1 %test, float* %bitcast, float* %ptr
   %loaded = load float* %select, align 4
   ret float %loaded
 }

 define i32 @test12(i32 %x, i32* %p) {
 ; Ensure we don't crash or fail to nuke dead selects of allocas if no load is
 ; never found.
 ; CHECK: @test12
 ; CHECK-NOT: alloca
 ; CHECK-NOT: select
 ; CHECK: ret i32 %x

 entry:
   %a = alloca i32
   store i32 %x, i32* %a
   %dead = select i1 undef, i32* %a, i32* %p
   %load = load i32* %a
   ret i32 %load
 }

 define i32 @test13(i32 %x, i32* %p) {
 ; Ensure we don't crash or fail to nuke dead phis of allocas if no load is ever
 ; found.
 ; CHECK: @test13
 ; CHECK-NOT: alloca
 ; CHECK-NOT: phi
 ; CHECK: ret i32 %x

 entry:
   %a = alloca i32
   store i32 %x, i32* %a
   br label %loop

 loop:
   %phi = phi i32* [ %p, %entry ], [ %a, %loop ]
   br i1 undef, label %loop, label %exit

 exit:
   %load = load i32* %a
   ret i32 %load
 }

 define i32 @PR13905() {
 ; Check a pattern where we have a chain of dead phi nodes to ensure they are
 ; deleted and promotion can proceed.
 ; CHECK: @PR13905
 ; CHECK-NOT: alloca i32
 ; CHECK: ret i32 undef

 entry:
   %h = alloca i32
   store i32 0, i32* %h
   br i1 undef, label %loop1, label %exit

 loop1:
   %phi1 = phi i32* [ null, %entry ], [ %h, %loop1 ], [ %h, %loop2 ]
   br i1 undef, label %loop1, label %loop2

 loop2:
   br i1 undef, label %loop1, label %exit

 exit:
   %phi2 = phi i32* [ %phi1, %loop2 ], [ null, %entry ]
   ret i32 undef
 }

 define i32 @PR13906() {
 ; Another pattern which can lead to crashes due to failing to clear out dead
 ; PHI nodes or select nodes. This triggers subtly differently from the above
 ; cases because the PHI node is (recursively) alive, but the select is dead.
 ; CHECK: @PR13906
 ; CHECK-NOT: alloca

 entry:
   %c = alloca i32
   store i32 0, i32* %c
   br label %for.cond

 for.cond:
   %d.0 = phi i32* [ undef, %entry ], [ %c, %if.then ], [ %d.0, %for.cond ]
   br i1 undef, label %if.then, label %for.cond

 if.then:
   %tmpcast.d.0 = select i1 undef, i32* %c, i32* %d.0
   br label %for.cond
 }

 define i64 @PR14132(i1 %flag) {
 ; CHECK: @PR14132
 ; Here we form a PHI-node by promoting the pointer alloca first, and then in
 ; order to promote the other two allocas, we speculate the load of the
 ; now-phi-node-pointer. In doing so we end up loading a 64-bit value from an i8
 ; alloca. While this is a bit dubious, we were asserting on trying to
 ; rewrite it. The trick is that the code using the value may carefully take
 ; steps to only use the not-undef bits, and so we need to at least loosely
 ; support this..
 entry:
   %a = alloca i64
   %b = alloca i8
   %ptr = alloca i64*
 ; CHECK-NOT: alloca

   %ptr.cast = bitcast i64** %ptr to i8**
   store i64 0, i64* %a
   store i8 1, i8* %b
   store i64* %a, i64** %ptr
   br i1 %flag, label %if.then, label %if.end

 if.then:
   store i8* %b, i8** %ptr.cast
   br label %if.end
 ; CHECK-NOT: store
 ; CHECK: %[[ext:.*]] = zext i8 1 to i64

 if.end:
   %tmp = load i64** %ptr
   %result = load i64* %tmp
 ; CHECK-NOT: load
 ; CHECK: %[[result:.*]] = phi i64 [ %[[ext]], %if.then ], [ 0, %entry ]

   ret i64 %result
 ; CHECK-NEXT: ret i64 %[[result]]
 }
	; RUN: opt < %s -sroa -S \| FileCheck %s
	target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n8:16:32:64"

	define i32 @test1() {
	; CHECK: @test1
	entry:
	%a = alloca [2 x i32]
	; CHECK-NOT: alloca

	%a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
	%a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
	store i32 0, i32* %a0
	store i32 1, i32* %a1
	%v0 = load i32* %a0
	%v1 = load i32* %a1
	; CHECK-NOT: store
	; CHECK-NOT: load

	%cond = icmp sle i32 %v0, %v1
	br i1 %cond, label %then, label %exit

	then:
	br label %exit

	exit:
	%phi = phi i32* [ %a1, %then ], [ %a0, %entry ]
	; CHECK: phi i32 [ 1, %{{.}} ], [ 0, %{{.}} ]

	%result = load i32* %phi
	ret i32 %result
	}

	define i32 @test2() {
	; CHECK: @test2
	entry:
	%a = alloca [2 x i32]
	; CHECK-NOT: alloca

	%a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
	%a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
	store i32 0, i32* %a0
	store i32 1, i32* %a1
	%v0 = load i32* %a0
	%v1 = load i32* %a1
	; CHECK-NOT: store
	; CHECK-NOT: load

	%cond = icmp sle i32 %v0, %v1
	%select = select i1 %cond, i32* %a1, i32* %a0
	; CHECK: select i1 %{{.*}}, i32 1, i32 0

	%result = load i32* %select
	ret i32 %result
	}

	define i32 @test3(i32 %x) {
	; CHECK: @test3
	entry:
	%a = alloca [2 x i32]
	; CHECK-NOT: alloca

	; Note that we build redundant GEPs here to ensure that having different GEPs
	; into the same alloca partation continues to work with PHI speculation. This
	; was the underlying cause of PR13926.
	%a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
	%a0b = getelementptr [2 x i32]* %a, i64 0, i32 0
	%a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
	%a1b = getelementptr [2 x i32]* %a, i64 0, i32 1
	store i32 0, i32* %a0
	store i32 1, i32* %a1
	; CHECK-NOT: store

	switch i32 %x, label %bb0 [ i32 1, label %bb1
	i32 2, label %bb2
	i32 3, label %bb3
	i32 4, label %bb4
	i32 5, label %bb5
	i32 6, label %bb6
	i32 7, label %bb7 ]

	bb0:
	br label %exit
	bb1:
	br label %exit
	bb2:
	br label %exit
	bb3:
	br label %exit
	bb4:
	br label %exit
	bb5:
	br label %exit
	bb6:
	br label %exit
	bb7:
	br label %exit

	exit:
	%phi = phi i32* [ %a1, %bb0 ], [ %a0, %bb1 ], [ %a0, %bb2 ], [ %a1, %bb3 ],
	[ %a1b, %bb4 ], [ %a0b, %bb5 ], [ %a0b, %bb6 ], [ %a1b, %bb7 ]
	; CHECK: phi i32 [ 1, %{{.}} ], [ 0, %{{.}} ], [ 0, %{{.}} ], [ 1, %{{.}} ], [ 1, %{{.}} ], [ 0, %{{.}} ], [ 0, %{{.}} ], [ 1, %{{.}} ]

	%result = load i32* %phi
	ret i32 %result
	}

	define i32 @test4() {
	; CHECK: @test4
	entry:
	%a = alloca [2 x i32]
	; CHECK-NOT: alloca

	%a0 = getelementptr [2 x i32]* %a, i64 0, i32 0
	%a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
	store i32 0, i32* %a0
	store i32 1, i32* %a1
	%v0 = load i32* %a0
	%v1 = load i32* %a1
	; CHECK-NOT: store
	; CHECK-NOT: load

	%cond = icmp sle i32 %v0, %v1
	%select = select i1 %cond, i32* %a0, i32* %a0
	; CHECK-NOT: select

	%result = load i32* %select
	ret i32 %result
	; CHECK: ret i32 0
	}

	define i32 @test5(i32* %b) {
	; CHECK: @test5
	entry:
	%a = alloca [2 x i32]
	; CHECK-NOT: alloca

	%a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
	store i32 1, i32* %a1
	; CHECK-NOT: store

	%select = select i1 true, i32* %a1, i32* %b
	; CHECK-NOT: select

	%result = load i32* %select
	; CHECK-NOT: load

	ret i32 %result
	; CHECK: ret i32 1
	}

	declare void @f(i32, i32)

	define i32 @test6(i32* %b) {
	; CHECK: @test6
	entry:
	%a = alloca [2 x i32]
	%c = alloca i32
	; CHECK-NOT: alloca

	%a1 = getelementptr [2 x i32]* %a, i64 0, i32 1
	store i32 1, i32* %a1

	%select = select i1 true, i32* %a1, i32* %b
	%select2 = select i1 false, i32* %a1, i32* %b
	%select3 = select i1 false, i32* %c, i32* %b
	; CHECK: %[[select2:.]] = select i1 false, i32 undef, i32* %b
	; CHECK: %[[select3:.]] = select i1 false, i32 undef, i32* %b

	; Note, this would potentially escape the alloca pointer except for the
	; constant folding of the select.
	call void @f(i32* %select2, i32* %select3)
	; CHECK: call void @f(i32* %[[select2]], i32* %[[select3]])


	%result = load i32* %select
	; CHECK-NOT: load

	%dead = load i32* %c

	ret i32 %result
	; CHECK: ret i32 1
	}

	define i32 @test7() {
	; CHECK: @test7
	; CHECK-NOT: alloca

	entry:
	%X = alloca i32
	br i1 undef, label %good, label %bad

	good:
	%Y1 = getelementptr i32* %X, i64 0
	store i32 0, i32* %Y1
	br label %exit

	bad:
	%Y2 = getelementptr i32* %X, i64 1
	store i32 0, i32* %Y2
	br label %exit

	exit:
	%P = phi i32* [ %Y1, %good ], [ %Y2, %bad ]
	; CHECK: %[[phi:.*]] = phi i32 [ 0, %good ],
	%Z2 = load i32* %P
	ret i32 %Z2
	; CHECK: ret i32 %[[phi]]
	}

	define i32 @test8(i32 %b, i32* %ptr) {
	; Ensure that we rewrite allocas to the used type when that use is hidden by
	; a PHI that can be speculated.
	; CHECK: @test8
	; CHECK-NOT: alloca
	; CHECK-NOT: load
	; CHECK: %[[value:.]] = load i32 %ptr
	; CHECK-NOT: load
	; CHECK: %[[result:.*]] = phi i32 [ undef, %else ], [ %[[value]], %then ]
	; CHECK-NEXT: ret i32 %[[result]]

	entry:
	%f = alloca float
	%test = icmp ne i32 %b, 0
	br i1 %test, label %then, label %else

	then:
	br label %exit

	else:
	%bitcast = bitcast float* %f to i32*
	br label %exit

	exit:
	%phi = phi i32* [ %bitcast, %else ], [ %ptr, %then ]
	%loaded = load i32* %phi, align 4
	ret i32 %loaded
	}

	define i32 @test9(i32 %b, i32* %ptr) {
	; Same as @test8 but for a select rather than a PHI node.
	; CHECK: @test9
	; CHECK-NOT: alloca
	; CHECK-NOT: load
	; CHECK: %[[value:.]] = load i32 %ptr
	; CHECK-NOT: load
	; CHECK: %[[result:.]] = select i1 %{{.}}, i32 undef, i32 %[[value]]
	; CHECK-NEXT: ret i32 %[[result]]

	entry:
	%f = alloca float
	store i32 0, i32* %ptr
	%test = icmp ne i32 %b, 0
	%bitcast = bitcast float* %f to i32*
	%select = select i1 %test, i32* %bitcast, i32* %ptr
	%loaded = load i32* %select, align 4
	ret i32 %loaded
	}

	define float @test10(i32 %b, float* %ptr) {
	; Don't try to promote allocas which are not elligible for it even after
	; rewriting due to the necessity of inserting bitcasts when speculating a PHI
	; node.
	; CHECK: @test10
	; CHECK: %[[alloca:.*]] = alloca
	; CHECK: %[[argvalue:.]] = load float %ptr
	; CHECK: %[[cast:.]] = bitcast double %[[alloca]] to float*
	; CHECK: %[[allocavalue:.]] = load float %[[cast]]
	; CHECK: %[[result:.*]] = phi float [ %[[allocavalue]], %else ], [ %[[argvalue]], %then ]
	; CHECK-NEXT: ret float %[[result]]

	entry:
	%f = alloca double
	store double 0.0, double* %f
	%test = icmp ne i32 %b, 0
	br i1 %test, label %then, label %else

	then:
	br label %exit

	else:
	%bitcast = bitcast double* %f to float*
	br label %exit

	exit:
	%phi = phi float* [ %bitcast, %else ], [ %ptr, %then ]
	%loaded = load float* %phi, align 4
	ret float %loaded
	}

	define float @test11(i32 %b, float* %ptr) {
	; Same as @test10 but for a select rather than a PHI node.
	; CHECK: @test11
	; CHECK: %[[alloca:.*]] = alloca
	; CHECK: %[[cast:.]] = bitcast double %[[alloca]] to float*
	; CHECK: %[[allocavalue:.]] = load float %[[cast]]
	; CHECK: %[[argvalue:.]] = load float %ptr
	; CHECK: %[[result:.]] = select i1 %{{.}}, float %[[allocavalue]], float %[[argvalue]]
	; CHECK-NEXT: ret float %[[result]]

	entry:
	%f = alloca double
	store double 0.0, double* %f
	store float 0.0, float* %ptr
	%test = icmp ne i32 %b, 0
	%bitcast = bitcast double* %f to float*
	%select = select i1 %test, float* %bitcast, float* %ptr
	%loaded = load float* %select, align 4
	ret float %loaded
	}

	define i32 @test12(i32 %x, i32* %p) {
	; Ensure we don't crash or fail to nuke dead selects of allocas if no load is
	; never found.
	; CHECK: @test12
	; CHECK-NOT: alloca
	; CHECK-NOT: select
	; CHECK: ret i32 %x

	entry:
	%a = alloca i32
	store i32 %x, i32* %a
	%dead = select i1 undef, i32* %a, i32* %p
	%load = load i32* %a
	ret i32 %load
	}

	define i32 @test13(i32 %x, i32* %p) {
	; Ensure we don't crash or fail to nuke dead phis of allocas if no load is ever
	; found.
	; CHECK: @test13
	; CHECK-NOT: alloca
	; CHECK-NOT: phi
	; CHECK: ret i32 %x

	entry:
	%a = alloca i32
	store i32 %x, i32* %a
	br label %loop

	loop:
	%phi = phi i32* [ %p, %entry ], [ %a, %loop ]
	br i1 undef, label %loop, label %exit

	exit:
	%load = load i32* %a
	ret i32 %load
	}

	define i32 @PR13905() {
	; Check a pattern where we have a chain of dead phi nodes to ensure they are
	; deleted and promotion can proceed.
	; CHECK: @PR13905
	; CHECK-NOT: alloca i32
	; CHECK: ret i32 undef

	entry:
	%h = alloca i32
	store i32 0, i32* %h
	br i1 undef, label %loop1, label %exit

	loop1:
	%phi1 = phi i32* [ null, %entry ], [ %h, %loop1 ], [ %h, %loop2 ]
	br i1 undef, label %loop1, label %loop2

	loop2:
	br i1 undef, label %loop1, label %exit

	exit:
	%phi2 = phi i32* [ %phi1, %loop2 ], [ null, %entry ]
	ret i32 undef
	}

	define i32 @PR13906() {
	; Another pattern which can lead to crashes due to failing to clear out dead
	; PHI nodes or select nodes. This triggers subtly differently from the above
	; cases because the PHI node is (recursively) alive, but the select is dead.
	; CHECK: @PR13906
	; CHECK-NOT: alloca

	entry:
	%c = alloca i32
	store i32 0, i32* %c
	br label %for.cond

	for.cond:
	%d.0 = phi i32* [ undef, %entry ], [ %c, %if.then ], [ %d.0, %for.cond ]
	br i1 undef, label %if.then, label %for.cond

	if.then:
	%tmpcast.d.0 = select i1 undef, i32* %c, i32* %d.0
	br label %for.cond
	}

	define i64 @PR14132(i1 %flag) {
	; CHECK: @PR14132
	; Here we form a PHI-node by promoting the pointer alloca first, and then in
	; order to promote the other two allocas, we speculate the load of the
	; now-phi-node-pointer. In doing so we end up loading a 64-bit value from an i8
	; alloca. While this is a bit dubious, we were asserting on trying to
	; rewrite it. The trick is that the code using the value may carefully take
	; steps to only use the not-undef bits, and so we need to at least loosely
	; support this..
	entry:
	%a = alloca i64
	%b = alloca i8
	%ptr = alloca i64*
	; CHECK-NOT: alloca

	%ptr.cast = bitcast i64 %ptr to i8
	store i64 0, i64* %a
	store i8 1, i8* %b
	store i64* %a, i64** %ptr
	br i1 %flag, label %if.then, label %if.end

	if.then:
	store i8* %b, i8** %ptr.cast
	br label %if.end
	; CHECK-NOT: store
	; CHECK: %[[ext:.*]] = zext i8 1 to i64

	if.end:
	%tmp = load i64** %ptr
	%result = load i64* %tmp
	; CHECK-NOT: load
	; CHECK: %[[result:.*]] = phi i64 [ %[[ext]], %if.then ], [ 0, %entry ]

	ret i64 %result
	; CHECK-NEXT: ret i64 %[[result]]
	}