[PATCH] D119640: [Transforms] InstCombineAddSub: Fix missing nsw/nuw flags

[Dmitry Vassiliev via Phabricator via llvm-commits]

slydiman created this revision.
slydiman added reviewers: kovdan01, asavonic, krisb.
slydiman added a project: LLVM.
Herald added a subscriber: hiraditya.
slydiman requested review of this revision.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119640

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/test/Transforms/InstCombine/add5.ll


Index: llvm/test/Transforms/InstCombine/add5.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/add5.ll
@@ -0,0 +1,21 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+;; -A + -B --> -(A + B)
+define dso_local i32 @test_neg_add_nsw(i32 %A, i32 %B) #0 {
+; CHECK-LABEL: @test_neg_add_nsw(
+; CHECK-NEXT:entry:
+; CHECK-NEXT:  %0 = add nsw i32 %A, %B
+; CHECK-NEXT:  %add = sub i32 0, %0
+; CHECK-NEXT:  ret i32 %add
+entry:
+  %B.addr = alloca i32, align 4
+  %A.addr = alloca i32, align 4
+  store i32 %B, i32* %B.addr, align 4
+  store i32 %A, i32* %A.addr, align 4
+  %0 = load i32, i32* %A.addr, align 4
+  %sub = sub nsw i32 0, %0
+  %1 = load i32, i32* %B.addr, align 4
+  %sub1 = sub nsw i32 0, %1
+  %add = add nsw i32 %sub, %sub1
+  ret i32 %add
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1321,7 +1321,8 @@
   if (match(LHS, m_Neg(m_Value(A)))) {
     // -A + -B --> -(A + B)
     if (match(RHS, m_Neg(m_Value(B))))
-      return BinaryOperator::CreateNeg(Builder.CreateAdd(A, B));
+      return BinaryOperator::CreateNeg(Builder.CreateAdd(
+          A, B, "", I.hasNoUnsignedWrap(), I.hasNoSignedWrap()));
 
     // -A + B --> B - A
     return BinaryOperator::CreateSub(RHS, A);


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