[llvm] [Reassociate] Move Disjoint flag handling to OverflowTracking. (PR #140406)

[Florian Hahn via llvm-commits]

https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/140406

>From fc13f3342ffbf1198ab1efd11a73bb61be88ae3f Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Sat, 17 May 2025 20:51:44 +0100
Subject: [PATCH] [Reassociate] Move Disjoint flag handling to
 OverflowTracking.

Move disjoint flag tracking to OverflowTracking. This enables preserving
disjoint flags in Reassociate.

Depends on https://github.com/llvm/llvm-project/pull/140404
---
 llvm/include/llvm/Transforms/Utils/Local.h      | 1 +
 llvm/lib/Transforms/Scalar/LICM.cpp             | 7 -------
 llvm/lib/Transforms/Utils/Local.cpp             | 4 ++++
 llvm/test/Transforms/Reassociate/or-disjoint.ll | 4 ++--
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index fa26446f9492a..9214aad4e6aec 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -563,6 +563,7 @@ bool inferAttributesFromOthers(Function &F);
 struct OverflowTracking {
   bool HasNUW = true;
   bool HasNSW = true;
+  bool IsDisjoint = true;
 
   // Note: At the moment, users are responsible to manage AllKnownNonNegative
   // and AllKnownNonZero manually. AllKnownNonNegative can be true in a case
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 7c7e0dcff0886..006a09b38bc71 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2870,13 +2870,6 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
     if (auto *I = dyn_cast<Instruction>(Inv))
       I->setFastMathFlags(Intersect);
     NewBO->setFastMathFlags(Intersect);
-  } else if (Opcode == Instruction::Or) {
-    bool Disjoint = cast<PossiblyDisjointInst>(BO)->isDisjoint() &&
-                    cast<PossiblyDisjointInst>(BO0)->isDisjoint();
-    // If `Inv` was not constant-folded, a new Instruction has been created.
-    if (auto *I = dyn_cast<PossiblyDisjointInst>(Inv))
-      I->setIsDisjoint(Disjoint);
-    cast<PossiblyDisjointInst>(NewBO)->setIsDisjoint(Disjoint);
   } else {
     OverflowTracking Flags;
     Flags.AllKnownNonNegative = false;
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 4d168ce7cf591..69dcd30d1af99 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -4368,6 +4368,8 @@ void OverflowTracking::mergeFlags(Instruction &I) {
     HasNUW &= I.hasNoUnsignedWrap();
     HasNSW &= I.hasNoSignedWrap();
   }
+  if (auto *DisjointOp = dyn_cast<PossiblyDisjointInst>(&I))
+    IsDisjoint &= DisjointOp->isDisjoint();
 }
 
 void OverflowTracking::applyFlags(Instruction &I) {
@@ -4379,4 +4381,6 @@ void OverflowTracking::applyFlags(Instruction &I) {
     if (HasNSW && (AllKnownNonNegative || HasNUW))
       I.setHasNoSignedWrap();
   }
+  if (auto *DisjointOp = dyn_cast<PossiblyDisjointInst>(&I))
+    DisjointOp->setIsDisjoint(IsDisjoint);
 }
diff --git a/llvm/test/Transforms/Reassociate/or-disjoint.ll b/llvm/test/Transforms/Reassociate/or-disjoint.ll
index 777836ed98152..b060b94e01d69 100644
--- a/llvm/test/Transforms/Reassociate/or-disjoint.ll
+++ b/llvm/test/Transforms/Reassociate/or-disjoint.ll
@@ -4,8 +4,8 @@
 
 define i16 @or_disjoint_both(i16 %a, i16 %b) {
 ; CHECK-LABEL: @or_disjoint_both(
-; CHECK-NEXT:    [[OR_1:%.*]] = or i16 [[A:%.*]], 1
-; CHECK-NEXT:    [[OR_2:%.*]] = or i16 [[OR_1]], [[B:%.*]]
+; CHECK-NEXT:    [[OR_1:%.*]] = or disjoint i16 [[A:%.*]], 1
+; CHECK-NEXT:    [[OR_2:%.*]] = or disjoint i16 [[OR_1]], [[B:%.*]]
 ; CHECK-NEXT:    ret i16 [[OR_2]]
 ;
   %or.1 = or disjoint i16 %b, %a