[llvm] [InstCombine] Drop nsw in negation of select (PR #112893)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 18 05:20:54 PDT 2024
https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/112893
Closes https://github.com/llvm/llvm-project/issues/112666.
>From 41aefe5a093de5699fa6483bdd31a737e938fb0b Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Fri, 18 Oct 2024 20:10:49 +0800
Subject: [PATCH 1/2] [InstCombine] Add pre-commit tests. NFC.
---
.../InstCombine/sub-of-negatible.ll | 42 +++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/sub-of-negatible.ll b/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
index b19eae4d8f9a41..83c70d62b3aed5 100644
--- a/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
+++ b/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
@@ -1374,6 +1374,48 @@ define i8 @negate_select_of_op_vs_negated_op(i8 %x, i8 %y, i1 %c) {
%t2 = sub i8 %y, %t1
ret i8 %t2
}
+
+define i8 @negate_select_of_op_vs_negated_op_nsw(i8 %x, i8 %y, i1 %c) {
+; CHECK-LABEL: @negate_select_of_op_vs_negated_op_nsw(
+; CHECK-NEXT: [[T0:%.*]] = sub nsw i8 0, [[X:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C:%.*]], i8 [[X]], i8 [[T0]]
+; CHECK-NEXT: [[T2:%.*]] = add i8 [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT: ret i8 [[T2]]
+;
+ %t0 = sub nsw i8 0, %x
+ %t1 = select i1 %c, i8 %t0, i8 %x
+ %t2 = sub i8 %y, %t1
+ ret i8 %t2
+}
+
+define i8 @negate_select_of_op_vs_negated_op_nsw_commuted(i8 %x, i8 %y, i1 %c) {
+; CHECK-LABEL: @negate_select_of_op_vs_negated_op_nsw_commuted(
+; CHECK-NEXT: [[T0:%.*]] = sub nsw i8 0, [[X:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C:%.*]], i8 [[T0]], i8 [[X]]
+; CHECK-NEXT: [[T2:%.*]] = add i8 [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT: ret i8 [[T2]]
+;
+ %t0 = sub nsw i8 0, %x
+ %t1 = select i1 %c, i8 %x, i8 %t0
+ %t2 = sub i8 %y, %t1
+ ret i8 %t2
+}
+
+define i8 @negate_select_of_op_vs_negated_op_nsw_xyyx(i8 %x, i8 %y, i8 %z, i1 %c) {
+; CHECK-LABEL: @negate_select_of_op_vs_negated_op_nsw_xyyx(
+; CHECK-NEXT: [[SUB1:%.*]] = sub nsw i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[SUB2:%.*]] = sub nsw i8 [[Y]], [[X]]
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C:%.*]], i8 [[SUB2]], i8 [[SUB1]]
+; CHECK-NEXT: [[T2:%.*]] = add i8 [[TMP1]], [[Z:%.*]]
+; CHECK-NEXT: ret i8 [[T2]]
+;
+ %sub1 = sub nsw i8 %x, %y
+ %sub2 = sub nsw i8 %y, %x
+ %t1 = select i1 %c, i8 %sub1, i8 %sub2
+ %t2 = sub i8 %z, %t1
+ ret i8 %t2
+}
+
define i8 @dont_negate_ordinary_select(i8 %x, i8 %y, i8 %z, i1 %c) {
; CHECK-LABEL: @dont_negate_ordinary_select(
; CHECK-NEXT: [[T0:%.*]] = select i1 [[C:%.*]], i8 [[X:%.*]], i8 [[Y:%.*]]
>From 8d86a537ad756e31832eab67371179e881452fb5 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Fri, 18 Oct 2024 20:19:53 +0800
Subject: [PATCH 2/2] [InstCombine] Drop nsw in negation of select
---
.../lib/Transforms/InstCombine/InstCombineNegator.cpp | 11 +++++++++++
llvm/test/Transforms/InstCombine/sub-of-negatible.ll | 8 ++++----
2 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp b/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
index 92293ef401465b..1d7ab84f19bd55 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
@@ -334,6 +334,17 @@ std::array<Value *, 2> Negator::getSortedOperandsOfBinOp(Instruction *I) {
NewSelect->swapValues();
// Don't swap prof metadata, we didn't change the branch behavior.
NewSelect->setName(I->getName() + ".neg");
+ // Poison-generating flags should be dropped
+ Value *TV = NewSelect->getTrueValue();
+ Value *FV = NewSelect->getFalseValue();
+ if (match(TV, m_Neg(m_Specific(FV))))
+ cast<Instruction>(TV)->dropPoisonGeneratingFlags();
+ else if (match(FV, m_Neg(m_Specific(TV))))
+ cast<Instruction>(FV)->dropPoisonGeneratingFlags();
+ else {
+ cast<Instruction>(TV)->dropPoisonGeneratingFlags();
+ cast<Instruction>(FV)->dropPoisonGeneratingFlags();
+ }
Builder.Insert(NewSelect);
return NewSelect;
}
diff --git a/llvm/test/Transforms/InstCombine/sub-of-negatible.ll b/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
index 83c70d62b3aed5..533db3144630ea 100644
--- a/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
+++ b/llvm/test/Transforms/InstCombine/sub-of-negatible.ll
@@ -1377,7 +1377,7 @@ define i8 @negate_select_of_op_vs_negated_op(i8 %x, i8 %y, i1 %c) {
define i8 @negate_select_of_op_vs_negated_op_nsw(i8 %x, i8 %y, i1 %c) {
; CHECK-LABEL: @negate_select_of_op_vs_negated_op_nsw(
-; CHECK-NEXT: [[T0:%.*]] = sub nsw i8 0, [[X:%.*]]
+; CHECK-NEXT: [[T0:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C:%.*]], i8 [[X]], i8 [[T0]]
; CHECK-NEXT: [[T2:%.*]] = add i8 [[TMP1]], [[Y:%.*]]
; CHECK-NEXT: ret i8 [[T2]]
@@ -1390,7 +1390,7 @@ define i8 @negate_select_of_op_vs_negated_op_nsw(i8 %x, i8 %y, i1 %c) {
define i8 @negate_select_of_op_vs_negated_op_nsw_commuted(i8 %x, i8 %y, i1 %c) {
; CHECK-LABEL: @negate_select_of_op_vs_negated_op_nsw_commuted(
-; CHECK-NEXT: [[T0:%.*]] = sub nsw i8 0, [[X:%.*]]
+; CHECK-NEXT: [[T0:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C:%.*]], i8 [[T0]], i8 [[X]]
; CHECK-NEXT: [[T2:%.*]] = add i8 [[TMP1]], [[Y:%.*]]
; CHECK-NEXT: ret i8 [[T2]]
@@ -1403,8 +1403,8 @@ define i8 @negate_select_of_op_vs_negated_op_nsw_commuted(i8 %x, i8 %y, i1 %c) {
define i8 @negate_select_of_op_vs_negated_op_nsw_xyyx(i8 %x, i8 %y, i8 %z, i1 %c) {
; CHECK-LABEL: @negate_select_of_op_vs_negated_op_nsw_xyyx(
-; CHECK-NEXT: [[SUB1:%.*]] = sub nsw i8 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[SUB2:%.*]] = sub nsw i8 [[Y]], [[X]]
+; CHECK-NEXT: [[SUB1:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[SUB2:%.*]] = sub i8 [[Y]], [[X]]
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C:%.*]], i8 [[SUB2]], i8 [[SUB1]]
; CHECK-NEXT: [[T2:%.*]] = add i8 [[TMP1]], [[Z:%.*]]
; CHECK-NEXT: ret i8 [[T2]]
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