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Sink: Don't sink static allocas from the entry block

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CodeGen treats allocas outside the entry block as dynamically sized
stack objects.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204473 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tom Stellard 2014-03-21 15:51:51 +00:00
parent 20115c69f5
commit 1b05bb2900
2 changed files with 86 additions and 0 deletions
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7
lib/Transforms/Scalar/Sink.cpp
View File

@ -216,6 +216,13 @@ bool Sinking::IsAcceptableTarget(Instruction *Inst,
/// instruction out of its current block into a successor.
bool Sinking::SinkInstruction(Instruction *Inst,
SmallPtrSet<Instruction *, 8> &Stores) {
// Don't sink static alloca instructions. CodeGen assumes allocas outside the
// entry block are dynamically sized stack objects.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
if (AI->isStaticAlloca())
return false;
// Check if it's safe to move the instruction.
if (!isSafeToMove(Inst, AA, Stores))
return false;

79
test/Transforms/Sink/basic.ll
View File

@ -62,3 +62,82 @@ X: ; preds = %5, %3
ret i32 %R
}
; We shouldn't sink constant sized allocas from the entry block, since CodeGen
; interprets allocas outside the entry block as dynamically sized stack objects.
; CHECK-LABEL: @alloca_nosink
; CHECK: entry:
; CHECK-NEXT: alloca
define i32 @alloca_nosink(i32 %a, i32 %b) {
entry:
%0 = alloca i32
%1 = icmp ne i32 %a, 0
br i1 %1, label %if, label %endif
if:
%2 = getelementptr i32* %0, i32 1
store i32 0, i32* %0
store i32 1, i32* %2
%3 = getelementptr i32* %0, i32 %b
%4 = load i32* %3
ret i32 %4
endif:
ret i32 0
}
; Make sure we sink dynamic sized allocas
; CHECK-LABEL: @alloca_sink_dynamic
; CHECK: entry:
; CHECK-NOT: alloca
; CHECK: if:
; CHECK-NEXT: alloca
define i32 @alloca_sink_dynamic(i32 %a, i32 %b, i32 %size) {
entry:
%0 = alloca i32, i32 %size
%1 = icmp ne i32 %a, 0
br i1 %1, label %if, label %endif
if:
%2 = getelementptr i32* %0, i32 1
store i32 0, i32* %0
store i32 1, i32* %2
%3 = getelementptr i32* %0, i32 %b
%4 = load i32* %3
ret i32 %4
endif:
ret i32 0
}
; We also want to sink allocas that are not in the entry block. These
; will already be considered as dynamically sized stack objects, so sinking
; them does no further damage.
; CHECK-LABEL: @alloca_sink_nonentry
; CHECK: if0:
; CHECK-NOT: alloca
; CHECK: if:
; CHECK-NEXT: alloca
define i32 @alloca_sink_nonentry(i32 %a, i32 %b, i32 %c) {
entry:
%cmp = icmp ne i32 %c, 0
br i1 %cmp, label %endif, label %if0
if0:
%0 = alloca i32
%1 = icmp ne i32 %a, 0
br i1 %1, label %if, label %endif
if:
%2 = getelementptr i32* %0, i32 1
store i32 0, i32* %0
store i32 1, i32* %2
%3 = getelementptr i32* %0, i32 %b
%4 = load i32* %3
ret i32 %4
endif:
ret i32 0
}