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[InstCombine] Simplify compare abs(X) and X. #76385

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Jan 5, 2024
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[InstCombine] Simplify compare abs(X) and X. #76385

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26debb2
[InstCombine] Simplify compare abs(X) and X.
Z572 Dec 25, 2023
229ed58
fixup! [InstCombine] Simplify compare abs(X) and X.
Z572 Jan 5, 2024
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51 changes: 51 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6860,6 +6860,57 @@ Instruction *InstCombinerImpl::foldICmpCommutative(ICmpInst::Predicate Pred,
return foldICmpAddOpConst(X, *C, Pred);
}

// abs(X) >= X --> true
// abs(X) u<= X --> true
// abs(X) < X --> false
// abs(X) u> X --> false
// abs(X) u>= X --> IsIntMinPosion ? `X > -1`: `X u<= INTMIN`
// abs(X) <= X --> IsIntMinPosion ? `X > -1`: `X u<= INTMIN`
// abs(X) == X --> IsIntMinPosion ? `X > -1`: `X u<= INTMIN`
// abs(X) u< X --> IsIntMinPosion ? `X < 0` : `X > INTMIN`
// abs(X) > X --> IsIntMinPosion ? `X < 0` : `X > INTMIN`
// abs(X) != X --> IsIntMinPosion ? `X < 0` : `X > INTMIN`
{
Value *X;
Constant *C;
if (match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X), m_Constant(C))) &&
match(Op1, m_Specific(X))) {
Value *NullValue = Constant::getNullValue(X->getType());
Value *AllOnesValue = Constant::getAllOnesValue(X->getType());
const APInt SMin =
APInt::getSignedMinValue(X->getType()->getScalarSizeInBits());
bool IsIntMinPosion = C->isAllOnesValue();
switch (Pred) {
case CmpInst::ICMP_ULE:
case CmpInst::ICMP_SGE:
return replaceInstUsesWith(CxtI, ConstantInt::getTrue(CxtI.getType()));
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_SLT:
return replaceInstUsesWith(CxtI, ConstantInt::getFalse(CxtI.getType()));
case CmpInst::ICMP_UGE:
case CmpInst::ICMP_SLE:
case CmpInst::ICMP_EQ: {
return replaceInstUsesWith(
CxtI, IsIntMinPosion
? Builder.CreateICmpSGT(X, AllOnesValue)
: Builder.CreateICmpULT(
X, ConstantInt::get(X->getType(), SMin + 1)));
}
case CmpInst::ICMP_ULT:
case CmpInst::ICMP_SGT:
case CmpInst::ICMP_NE: {
return replaceInstUsesWith(
CxtI, IsIntMinPosion
? Builder.CreateICmpSLT(X, NullValue)
: Builder.CreateICmpUGT(
X, ConstantInt::get(X->getType(), SMin)));
}
default:
llvm_unreachable("Invalid predicate!");
}
}
}

return nullptr;
}

Expand Down
219 changes: 219 additions & 0 deletions llvm/test/Transforms/InstCombine/icmp-abs.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,219 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

declare i4 @llvm.abs.i4(i4, i1)

define i1 @icmp_sge_abs(i4 %arg) {
; CHECK-LABEL: @icmp_sge_abs(
; CHECK-NEXT: ret i1 true
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp sge i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_sge_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_sge_abs_false(
; CHECK-NEXT: ret i1 true
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp sge i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_eq_abs(i4 %arg) {
; CHECK-LABEL: @icmp_eq_abs(
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i4 [[ARG:%.*]], -1
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp eq i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_eq_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_eq_abs_false(
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i4 [[ARG:%.*]], -7
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp eq i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ne_abs(i4 %arg) {
; CHECK-LABEL: @icmp_ne_abs(
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i4 [[ARG:%.*]], 0
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp ne i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ne_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_ne_abs_false(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i4 [[ARG:%.*]], -8
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp ne i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_sle_abs(i4 %arg) {
; CHECK-LABEL: @icmp_sle_abs(
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i4 [[ARG:%.*]], -1
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp sle i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_sle_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_sle_abs_false(
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i4 [[ARG:%.*]], -7
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp sle i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_slt_abs(i4 %arg) {
; CHECK-LABEL: @icmp_slt_abs(
; CHECK-NEXT: ret i1 false
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp slt i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_slt_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_slt_abs_false(
; CHECK-NEXT: ret i1 false
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp slt i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_sgt_abs(i4 %arg) {
; CHECK-LABEL: @icmp_sgt_abs(
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i4 [[ARG:%.*]], 0
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp sgt i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_sgt_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_sgt_abs_false(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i4 [[ARG:%.*]], -8
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp sgt i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ugt_abs(i4 %arg) {
; CHECK-LABEL: @icmp_ugt_abs(
; CHECK-NEXT: ret i1 false
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp ugt i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ugt_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_ugt_abs_false(
; CHECK-NEXT: ret i1 false
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp ugt i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_uge_abs(i4 %arg) {
; CHECK-LABEL: @icmp_uge_abs(
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i4 [[ARG:%.*]], -1
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp uge i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_uge_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_uge_abs_false(
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i4 [[ARG:%.*]], -7
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp uge i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ule_abs(i4 %arg) {
; CHECK-LABEL: @icmp_ule_abs(
; CHECK-NEXT: ret i1 true
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp ule i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ule_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_ule_abs_false(
; CHECK-NEXT: ret i1 true
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp ule i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ult_abs(i4 %arg) {
; CHECK-LABEL: @icmp_ult_abs(
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i4 [[ARG:%.*]], 0
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp ult i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_ult_abs_false(i4 %arg) {
; CHECK-LABEL: @icmp_ult_abs_false(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i4 [[ARG:%.*]], -8
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 false)
%cmp = icmp ult i4 %abs, %arg
ret i1 %cmp
}

define i1 @icmp_sge_abs2(i4 %arg) {
; CHECK-LABEL: @icmp_sge_abs2(
; CHECK-NEXT: [[X:%.*]] = mul i4 [[ARG:%.*]], [[ARG]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i4 [[X]], -1
; CHECK-NEXT: ret i1 [[CMP]]
;
%x = mul i4 %arg, %arg ; thwart complexity-based canonicalization
%abs = call i4 @llvm.abs.i4(i4 %x, i1 true)
%cmp = icmp sge i4 %x, %abs
ret i1 %cmp
}

define i1 @icmp_sge_abs_mismatched_op(i4 %arg, i4 %arg2) {
; CHECK-LABEL: @icmp_sge_abs_mismatched_op(
; CHECK-NEXT: [[ABS:%.*]] = call i4 @llvm.abs.i4(i4 [[ARG:%.*]], i1 true)
; CHECK-NEXT: [[CMP:%.*]] = icmp sge i4 [[ABS]], [[ARG2:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%abs = call i4 @llvm.abs.i4(i4 %arg, i1 true)
%cmp = icmp sge i4 %abs, %arg2
ret i1 %cmp
}