[llvm] [InstCombine] Simplify compare abs(X) and X. (PR #76385)
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Tue Jan 2 08:19:30 PST 2024
https://github.com/Z572 updated https://github.com/llvm/llvm-project/pull/76385
>From 26debb25165b43df7a21a4802a751ae406af3e23 Mon Sep 17 00:00:00 2001
From: Zheng Junjie <zhengjunjie at iscas.ac.cn>
Date: Mon, 25 Dec 2023 23:47:31 +0800
Subject: [PATCH] [InstCombine] Simplify compare abs(X) and X.
proof: https://alive2.llvm.org/ce/z/LZzZaj
---
.../InstCombine/InstCombineCompares.cpp | 48 ++++
llvm/test/Transforms/InstCombine/icmp-abs.ll | 208 ++++++++++++++++++
2 files changed, 256 insertions(+)
create mode 100644 llvm/test/Transforms/InstCombine/icmp-abs.ll
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 3875e59c3ede3b..c0f87c7e509fb7 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -6860,6 +6860,54 @@ 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());
+ Value *MinVal = ConstantInt::get(
+ X->getType(),
+ 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.CreateICmpULE(X, MinVal));
+ }
+ case CmpInst::ICMP_ULT:
+ case CmpInst::ICMP_SGT:
+ case CmpInst::ICMP_NE: {
+ return replaceInstUsesWith(
+ CxtI, IsIntMinPosion ? Builder.CreateICmpSLT(X, NullValue)
+ : Builder.CreateICmpUGT(X, MinVal));
+ }
+ default:
+ llvm_unreachable("Invalid predicate!");
+ }
+ }
+ }
+
return nullptr;
}
diff --git a/llvm/test/Transforms/InstCombine/icmp-abs.ll b/llvm/test/Transforms/InstCombine/icmp-abs.ll
new file mode 100644
index 00000000000000..497c965a6a90fb
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/icmp-abs.ll
@@ -0,0 +1,208 @@
+; 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
+}
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