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Fold vector selects with undef elements in the condition. Fixes PR18319.

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Patch by Ilia Filippov!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198267 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2013-12-31 19:30:47 +00:00
parent 5cbbd7e1a5
commit 99cebadb5c
3 changed files with 24 additions and 7 deletions
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21
lib/IR/ConstantFold.cpp
View File

@ -705,12 +705,21 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
SmallVector<Constant*, 16> Result;
Type *Ty = IntegerType::get(CondV->getContext(), 32);
for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
ConstantInt *Cond = dyn_cast<ConstantInt>(CondV->getOperand(i));
if (Cond == 0) break;
Constant *V = Cond->isNullValue() ? V2 : V1;
Constant *Res = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
Result.push_back(Res);
Constant *V;
Constant *V1Element = ConstantExpr::getExtractElement(V1,
ConstantInt::get(Ty, i));
Constant *V2Element = ConstantExpr::getExtractElement(V2,
ConstantInt::get(Ty, i));
Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i));
if (V1Element == V2Element) {
V = V1Element;
} else if (isa<UndefValue>(Cond)) {
V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
} else {
if (!isa<ConstantInt>(Cond)) break;
V = Cond->isNullValue() ? V2Element : V1Element;
}
Result.push_back(V);
}
// If we were able to build the vector, return it.

8
test/Assembler/ConstantExprFoldSelect.ll Normal file
View File

@ -0,0 +1,8 @@
; RUN: llvm-as < %s | llvm-dis | FileCheck %s
; PR18319
define void @function() {
%c = trunc <4 x i16> select (<4 x i1> <i1 undef, i1 undef, i1 false, i1 true>, <4 x i16> <i16 undef, i16 2, i16 3, i16 4>, <4 x i16> <i16 -1, i16 -2, i16 -3, i16 -4>) to <4 x i8>
; CHECK: <i16 undef, i16 -2, i16 -3, i16 4>
ret void
}

2
test/Bitcode/select.ll
View File

@ -5,5 +5,5 @@ define <2 x i32> @main() {
}
; CHECK: define <2 x i32> @main() {
; CHECK: ret <2 x i32> select (<2 x i1> <i1 false, i1 undef>, <2 x i32> zeroinitializer, <2 x i32> <i32 0, i32 undef>)
; CHECK: ret <2 x i32> <i32 0, i32 undef>
; CHECK: }