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Try turning icmp(bitcast(x), bitcast(y)) into icmp(bitcast(bitcast(x)), y) in

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the hopes that the two bitcasts will merge.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82371 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2009-09-20 05:48:50 +00:00
parent 043b8b5bb2
commit 55a722bf6a
2 changed files with 15 additions and 0 deletions
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10
lib/VMCore/ConstantFold.cpp
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@ -1627,6 +1627,16 @@ Constant *llvm::ConstantFoldCompareInstruction(LLVMContext &Context,
if (Result != -1)
return ConstantInt::get(Type::getInt1Ty(Context), Result);
// If the right hand side is a bitcast, try using its inverse to simplify
// it by moving it to the left hand side.
if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
if (CE2->getOpcode() == Instruction::BitCast) {
Constant *CE2Op0 = CE2->getOperand(0);
Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
}
}
if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
// If C2 is a constant expr and C1 isn't, flip them around and fold the
// other way if possible.

5
test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
View File

@ -23,3 +23,8 @@ global i1 srem (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
global i1 urem (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
; CHECK-NOT: icmp
; CHECK: i1 false
global i1 icmp ule (i32* bitcast (i8* @X to i32*), i32* bitcast (i8* @Y to i32*))
; CHECK-NOT: bitcast
; CHECK: icmp