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Bitcasts are transitive. Bitcast-Bitcast-X becomes Bitcast-X.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138722 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem 2011-08-28 11:51:08 +00:00
parent b1b051ec97
commit be6ceb6ebc
3 changed files with 25 additions and 0 deletions
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6
lib/Analysis/ConstantFolding.cpp
View File

@ -51,6 +51,12 @@ static Constant *FoldBitCast(Constant *C, Type *DestTy,
if (C->isAllOnesValue() && !DestTy->isX86_MMXTy())
return Constant::getAllOnesValue(DestTy);
// Bitcast of Bitcast can be done using a single cast.
ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
if (CE && CE->getOpcode() == Instruction::BitCast) {
return ConstantExpr::getBitCast(CE->getOperand(0), DestTy);
}
// The code below only handles casts to vectors currently.
VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
if (DestVTy == 0)

5
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -1659,6 +1659,11 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
if (DestTy == Src->getType())
return ReplaceInstUsesWith(CI, Src);
// Bitcasts are transitive.
if (BitCastInst* BSrc = dyn_cast<BitCastInst>(Src)) {
return CastInst::Create(Instruction::BitCast, BSrc->getOperand(0), DestTy);
}
if (PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
PointerType *SrcPTy = cast<PointerType>(SrcTy);
Type *DstElTy = DstPTy->getElementType();

14
test/Transforms/InstCombine/cast.ll
View File

@ -630,3 +630,17 @@ entry:
; CHECK: uitofp
}
define <4 x float> @test64(<4 x float> %c) nounwind {
%t0 = bitcast <4 x float> %c to <4 x i32>
%t1 = bitcast <4 x i32> %t0 to <2 x double>
%t2 = bitcast <2 x double> %t1 to <4 x float>
ret <4 x float> %t2
; CHECK: @test64
; CHECK-NEXT: ret <4 x float> %c
}
define float @test2c() {
ret float extractelement (<2 x float> bitcast (double bitcast (<2 x float> <float -1.000000e+00, float -1.000000e+00> to double) to <2 x float>), i32 0)
; CHECK: @test2c
; CHECK-NOT: extractelement
}