[llvm] [VPlan] Directly unroll VectorPointerRecipe (PR #168886)

[Ramkumar Ramachandra via llvm-commits]

================
@@ -528,7 +528,8 @@ define void @multiple_exit_conditions(ptr %src, ptr noalias %dst) #1 {
 ; DEFAULT-NEXT:    br i1 [[MIN_ITERS_CHECK1]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
 ; DEFAULT:       [[VECTOR_PH]]:
 ; DEFAULT-NEXT:    [[TMP4:%.*]] = call i64 @llvm.vscale.i64()
-; DEFAULT-NEXT:    [[TMP5:%.*]] = mul nuw i64 [[TMP4]], 16
+; DEFAULT-NEXT:    [[TMP11:%.*]] = mul nuw i64 [[TMP4]], 4
+; DEFAULT-NEXT:    [[TMP5:%.*]] = mul i64 [[TMP11]], 4
----------------
artagnon wrote:

I noticed this one too, and the following planned follow-up will fix it. However, it needs to be a follow-up due to the test-updates.

```diff
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index 6d70180ccf20..dc72ace13048 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -4563,7 +4563,8 @@ void VPlanTransforms::materializeVFAndVFxUF(VPlan &Plan, VPBasicBlock *VectorPH,
   VF.replaceAllUsesWith(RuntimeVF);

   VPValue *UF = Plan.getConstantInt(TCTy, Plan.getUF());
-  VPValue *MulByUF = Builder.createNaryOp(Instruction::Mul, {RuntimeVF, UF});
+  VPValue *MulByUF = Builder.createOverflowingOp(Instruction::Mul,
+                                                 {RuntimeVF, UF}, {true, true});
   VFxUF.replaceAllUsesWith(MulByUF);
 }

@@ -4851,7 +4852,8 @@ void VPlanTransforms::narrowInterleaveGroups(VPlan &Plan, ElementCount VF,
   if (VF.isScalable()) {
     VPValue *VScale = PHBuilder.createElementCount(
         VectorLoop->getCanonicalIVType(), ElementCount::getScalable(1));
-    VPValue *VScaleUF = PHBuilder.createNaryOp(Instruction::Mul, {VScale, UF});
+    VPValue *VScaleUF = PHBuilder.createOverflowingOp(
+        Instruction::Mul, {VScale, UF}, {true, true});
     Inc->setOperand(1, VScaleUF);
     Plan.getVF().replaceAllUsesWith(VScale);
   } else {
```

https://github.com/llvm/llvm-project/pull/168886