[llvm] [DAG] Apply Disjoint flag. (PR #118045)

[via llvm-commits]

https://github.com/fengfeng09 created https://github.com/llvm/llvm-project/pull/118045

or disjoint (or disjoint (x, c0), c1)
-->
or disjont x, or (c0, c1)
Alive2: https://alive2.llvm.org/ce/z/3wPth5

>From 9a21e3832952877c1a7220ae0df2c6a1e562dedc Mon Sep 17 00:00:00 2001
From: "feng.feng" <feng.feng at iluvatar.com>
Date: Fri, 29 Nov 2024 11:17:54 +0800
Subject: [PATCH] [DAG] Apply Disjoint flag.

or disjoint (or disjoint (x, c0), c1)
-->
or disjont x, or (c0, c1)
Alive2: https://alive2.llvm.org/ce/z/3wPth5

Signed-off-by: feng.feng <feng.feng at iluvatar.com>
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 521829675ae7c3..f56930f08f68ef 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1220,8 +1220,11 @@ SDValue DAGCombiner::reassociateOpsCommutative(unsigned Opc, const SDLoc &DL,
 
     if (DAG.isConstantIntBuildVectorOrConstantInt(N1)) {
       // Reassociate: (op (op x, c1), c2) -> (op x, (op c1, c2))
-      if (SDValue OpNode = DAG.FoldConstantArithmetic(Opc, DL, VT, {N01, N1}))
+      if (SDValue OpNode = DAG.FoldConstantArithmetic(Opc, DL, VT, {N01, N1})) {
+        NewFlags.setDisjoint(Flags.hasDisjoint() &&
+                             N0->getFlags().hasDisjoint());
         return DAG.getNode(Opc, DL, VT, N00, OpNode, NewFlags);
+      }
       return SDValue();
     }
     if (TLI.isReassocProfitable(DAG, N0, N1)) {