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

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 <[email protected]>

Author: fengfeng09

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)) {

llvm/test/CodeGen/AArch64/apply-disjoint-flag-in-dagcombine.ll

@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=aarch64-none-eabi %s -o - | FileCheck %s
+
+define i32 @test(i32 %a) {
+; CHECK-LABEL: test:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    add w0, w0, #193
+; CHECK-NEXT:    ret
+entry:
+  %add = add i32 %a, 1
+  %or1 = or disjoint i32 %add, 64
+  %or = or disjoint i32 %or1, 128
+  ret i32 %or
+}