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Fold 'icmp eq (icmp), true' into an xor(icmp).

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82386 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2009-09-20 07:21:39 +00:00
parent e895c61515
commit 85958b059d
2 changed files with 23 additions and 0 deletions
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14
lib/VMCore/ConstantFold.cpp
View File

@ -1428,6 +1428,20 @@ Constant *llvm::ConstantFoldCompareInstruction(LLVMContext &Context,
}
}
// If the comparison is a comparison between two i1's, simplify it.
if (C1->getType() == Type::getInt1Ty(Context)) {
switch(pred) {
case ICmpInst::ICMP_EQ:
if (isa<ConstantInt>(C2))
return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
case ICmpInst::ICMP_NE:
return ConstantExpr::getXor(C1, C2);
default:
break;
}
}
if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
APInt V1 = cast<ConstantInt>(C1)->getValue();
APInt V2 = cast<ConstantInt>(C2)->getValue();

9
test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
View File

@ -27,3 +27,12 @@
; CHECK: @I = global i1 icmp ult (i8* @X, i8* @Y) ; <i1*> [#uses=0]
@J = global i1 xor (i1 icmp ult (i8* @X, i8* @Y), i1 true)
; CHECK: @J = global i1 icmp uge (i8* @X, i8* @Y) ; <i1*> [#uses=0]
@K = global i1 icmp eq (i1 icmp ult (i8* @X, i8* @Y), i1 false)
; CHECK: @K = global i1 icmp uge (i8* @X, i8* @Y) ; <i1*> [#uses=0]
@L = global i1 icmp eq (i1 icmp ult (i8* @X, i8* @Y), i1 true)
; CHECK: @L = global i1 icmp ult (i8* @X, i8* @Y) ; <i1*> [#uses=0]
@M = global i1 icmp ne (i1 icmp ult (i8* @X, i8* @Y), i1 true)
; CHECK: @M = global i1 icmp uge (i8* @X, i8* @Y) ; <i1*> [#uses=0]
@N = global i1 icmp ne (i1 icmp ult (i8* @X, i8* @Y), i1 false)
; CHECK: @N = global i1 icmp ult (i8* @X, i8* @Y) ; <i1*> [#uses=0]