[llvm] [LV] Use shl for (VFxUF * vscale) when creating minimum iter check. (PR #153495)

[Florian Hahn via llvm-commits]

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@@ -824,7 +824,13 @@ namespace llvm {
 Value *createStepForVF(IRBuilderBase &B, Type *Ty, ElementCount VF,
                        int64_t Step) {
   assert(Ty->isIntegerTy() && "Expected an integer step");
-  return B.CreateElementCount(Ty, VF.multiplyCoefficientBy(Step));
+  if (!VF.isScalable() || !isPowerOf2_64(VF.getKnownMinValue()) ||
+      !isPowerOf2_64(Step))
+    return B.CreateElementCount(Ty, VF.multiplyCoefficientBy(Step));
+
+  return B.CreateShl(
+      B.CreateVScale(Ty),
+      ConstantInt::get(Ty, Log2_64((VF * Step).getKnownMinValue())), "", true);
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fhahn wrote:

Updated thanks

https://github.com/llvm/llvm-project/pull/153495