[llvm] [VectorCombine] Use InstSimplifyFolder to simplify instrs on creation. (PR #146350)

[Ramkumar Ramachandra via llvm-commits]

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@@ -1459,10 +1461,12 @@ bool VectorCombine::foldBinopOfReductions(Instruction &I) {
   LLVM_DEBUG(dbgs() << "Found two mergeable reductions: " << I
                     << "\n  OldCost: " << OldCost << " vs NewCost: " << NewCost
                     << "\n");
-  Value *VectorBO = Builder.CreateBinOp(BinOpOpc, V0, V1);
-  if (auto *PDInst = dyn_cast<PossiblyDisjointInst>(&I))
-    if (auto *PDVectorBO = dyn_cast<PossiblyDisjointInst>(VectorBO))
-      PDVectorBO->setIsDisjoint(PDInst->isDisjoint());
+  Value *VectorBO;
+  if (BinOpOpc == Instruction::Or)
+    VectorBO = Builder.CreateOr(V0, V1, "",
+                                cast<PossiblyDisjointInst>(I).isDisjoint());
+  else
+    VectorBO = Builder.CreateBinOp(BinOpOpc, V0, V1);
----------------
artagnon wrote:

```suggestion
    VectorBO = isa<PossiblyDisjointInst>(I) ?
      Builder.CreateDisjoint(BinOpOpc, V0, V1) :
      Builder.CreateBinOp(BinOpOpc, V0, V1);
```

Better not to rely on just Or being PossiblyDisjoint.

https://github.com/llvm/llvm-project/pull/146350