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[InstSimplify] Odd - X ==/!= X -> false/true

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Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D132989
This commit is contained in:
LiaoChunyu
2022-09-05 23:30:52 +08:00
parent 14eea55445
commit 5e9522c311
2 changed files with 14 additions and 9 deletions
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11
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@@ -3126,6 +3126,17 @@ static Value *simplifyICmpWithBinOpOnLHS(CmpInst::Predicate Pred,
return getTrue(ITy);
}
// (sub C, X) == X, C is odd --> false
// (sub C, X) != X, C is odd --> true
if (match(LBO, m_Sub(m_APInt(C), m_Specific(RHS)))) {
if ((*C & 1) == 1) {
if (Pred == CmpInst::ICMP_EQ)
return ConstantInt::getFalse(getCompareTy(RHS));
if (Pred == CmpInst::ICMP_NE)
return ConstantInt::getTrue(getCompareTy(RHS));
}
}
return nullptr;
}

12
llvm/test/Transforms/InstSimplify/icmp.ll
View File

@@ -214,9 +214,7 @@ loop:
define i1 @sub_false(i32 %x) {
; CHECK-LABEL: @sub_false(
; CHECK-NEXT: [[SUB:%.*]] = sub i32 1, [[X:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[SUB]], [[X]]
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: ret i1 false
;
%sub = sub i32 1, %x
%cmp = icmp eq i32 %sub, %x
@@ -225,9 +223,7 @@ define i1 @sub_false(i32 %x) {
define i1 @sub_swap(i8 %x) {
; CHECK-LABEL: @sub_swap(
; CHECK-NEXT: [[SUB:%.*]] = sub i8 3, [[X:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[X]], [[SUB]]
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: ret i1 true
;
%sub = sub i8 3, %x
%cmp = icmp ne i8 %x, %sub
@@ -236,9 +232,7 @@ define i1 @sub_swap(i8 %x) {
define <2 x i1> @sub_odd(<2 x i8> %x) {
; CHECK-LABEL: @sub_odd(
; CHECK-NEXT: [[SUB:%.*]] = sub <2 x i8> <i8 3, i8 3>, [[X:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne <2 x i8> [[SUB]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[CMP]]
; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
;
%sub = sub <2 x i8> <i8 3, i8 3>, %x
%cmp = icmp ne <2 x i8> %sub, %x