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Peer through sext/zext when looking for not(cmp).

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llvm-svn: 51819
This commit is contained in:
Nick Lewycky 2008-05-31 19:01:33 +00:00
parent 566baa2c72
commit 1bcd80adf7
3 changed files with 20 additions and 27 deletions
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26
lib/Target/README.txt
View File

@ -775,32 +775,6 @@ be done safely if "b" isn't modified between the strlen and memcpy of course.
//===---------------------------------------------------------------------===//
define i32 @test2(float %X, float %Y) {
entry:
%tmp3 = fcmp uno float %X, %Y ; <i1> [#uses=1]
%tmp34 = zext i1 %tmp3 to i8 ; <i8> [#uses=1]
%tmp = xor i8 %tmp34, 1 ; <i8> [#uses=1]
%toBoolnot5 = zext i8 %tmp to i32 ; <i32> [#uses=1]
ret i32 %toBoolnot5
}
could be optimized further. Instcombine should use its bitwise analysis to
collapse the zext/xor/zext structure to an xor/zext and then remove the
xor by reversing the fcmp.
Desired output:
define i32 @test2(float %X, float %Y) {
entry:
%tmp3 = fcmp ord float %X, %Y ; <i1> [#uses=1]
%tmp34 = zext i1 %tmp3 to i32 ; <i32> [#uses=1]
ret i32 %tmp34
}
To fix this, we need to make CanEvaluateInDifferentType smarter.
//===---------------------------------------------------------------------===//
We should be able to evaluate this loop:
int test(int x_offs) {

20
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -5013,6 +5013,25 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
FCI->getOperand(0), FCI->getOperand(1));
}
// fold (xor(zext(cmp)), 1) and (xor(sext(cmp)), -1) to ext(!cmp).
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
if (CmpInst *CI = dyn_cast<CmpInst>(Op0C->getOperand(0))) {
if (CI->hasOneUse() && Op0C->hasOneUse()) {
Instruction::CastOps Opcode = Op0C->getOpcode();
if (Opcode == Instruction::ZExt || Opcode == Instruction::SExt) {
if (RHS == ConstantExpr::getCast(Opcode, ConstantInt::getTrue(),
Op0C->getDestTy())) {
Instruction *NewCI = InsertNewInstBefore(CmpInst::Create(
CI->getOpcode(), CI->getInversePredicate(),
CI->getOperand(0), CI->getOperand(1)), I);
NewCI->takeName(CI);
return CastInst::Create(Opcode, NewCI, Op0C->getType());
}
}
}
}
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
// ~(c-X) == X-c-1 == X+(-c-1)
if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
@ -5206,6 +5225,7 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
}
}
}
return Changed ? &I : 0;
}

1
test/Transforms/InstCombine/zext-fold.ll
View File

@ -1,6 +1,5 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {zext } | count 1
; PR1570
; XFAIL: *
define i32 @test2(float %X, float %Y) {
entry: