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instcombine: alloca: Canonicalize scalar allocation array size

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As a follow-up to r232200, add an `-instcombine` to canonicalize scalar
allocations to `i32 1`.  Since r232200, `iX 1` (for X != 32) are only
created by RAUWs, so this shouldn't fire too often.  Nevertheless, it's
a cheap check and a nice cleanup.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232202 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2015-03-13 19:42:09 +00:00
parent 5c71858076
commit d747f3f3fe
2 changed files with 12 additions and 4 deletions
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12
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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@ -166,8 +166,16 @@ isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
// Check for array size of 1 (scalar allocation).
if (!AI.isArrayAllocation())
return nullptr;
if (!AI.isArrayAllocation()) {
// i32 1 is the canonical array size for scalar allocations.
if (AI.getArraySize()->getType()->isIntegerTy(32))
return nullptr;
// Canonicalize it.
Value *V = IC.Builder->getInt32(1);
AI.setOperand(0, V);
return &AI;
}
// Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {

4
test/Transforms/InstCombine/alloca.ll
View File

@ -155,8 +155,8 @@ define void @test10() {
entry:
; ALL-LABEL: @test10(
; ALL: %v32 = alloca i1, align 8
; ALL: %v64 = alloca i1, i64 1, align 8
; ALL: %v33 = alloca i1, i33 1, align 8
; ALL: %v64 = alloca i1, align 8
; ALL: %v33 = alloca i1, align 8
%v32 = alloca i1, align 8
%v64 = alloca i1, i64 1, align 8
%v33 = alloca i1, i33 1, align 8