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[InstCombine] handle icmp i1 X, C early to avoid creating an unknown pattern 

The missing optimization for xor-of-icmps still needs to be added, but by
being more efficient (not generating unnecessary logic ops with constants)
we avoid the bug.

See discussion in post-commit comments:
https://reviews.llvm.org/D32143

llvm-svn: 303312
This commit is contained in:
Sanjay Patel 2017-05-17 22:29:40 +00:00
parent cde4b3f4e6
commit ba212c241a
2 changed files with 25 additions and 4 deletions
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23
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -4266,6 +4266,29 @@ static Instruction *canonicalizeICmpBool(ICmpInst &I,
Value *A = I.getOperand(0), *B = I.getOperand(1);
assert(A->getType()->getScalarType()->isIntegerTy(1) && "Bools only");
// A boolean compared to true/false can be simplified to Op0/true/false in
// 14 out of the 20 (10 predicates * 2 constants) possible combinations.
// Cases not handled by InstSimplify are always 'not' of Op0.
if (match(B, m_Zero())) {
switch (I.getPredicate()) {
case CmpInst::ICMP_EQ: // A == 0 -> !A
case CmpInst::ICMP_ULE: // A <=u 0 -> !A
case CmpInst::ICMP_SGE: // A >=s 0 -> !A
return BinaryOperator::CreateNot(A);
default:
llvm_unreachable("ICmp i1 X, C not simplified as expected.");
}
} else if (match(B, m_One())) {
switch (I.getPredicate()) {
case CmpInst::ICMP_NE: // A != 1 -> !A
case CmpInst::ICMP_ULT: // A <u 1 -> !A
case CmpInst::ICMP_SGT: // A >s -1 -> !A
return BinaryOperator::CreateNot(A);
default:
llvm_unreachable("ICmp i1 X, C not simplified as expected.");
}
}
switch (I.getPredicate()) {
default:
llvm_unreachable("Invalid icmp instruction!");

6
llvm/test/Transforms/InstCombine/set.ll
View File

@ -152,10 +152,8 @@ define <3 x i1> @test14vec(<3 x i1> %A, <3 x i1> %B) {
define i1 @bool_eq0(i64 %a) {
; CHECK-LABEL: @bool_eq0(
; CHECK-NEXT: [[B:%.*]] = icmp sgt i64 %a, 0
; CHECK-NEXT: [[C:%.*]] = icmp eq i64 %a, 1
; CHECK-NEXT: [[AND:%.*]] = xor i1 [[C]], [[B]]
; CHECK-NEXT: ret i1 [[AND]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i64 %a, 1
; CHECK-NEXT: ret i1 [[TMP1]]
;
%b = icmp sgt i64 %a, 0
%c = icmp eq i64 %a, 1