[llvm] [VPlan] Add VPValue for VF, use it for VPWidenIntOrFpInductionRecipe. (PR #95305)

[Florian Hahn via llvm-commits]

================
@@ -934,8 +934,19 @@ void VPlan::prepareToExecute(Value *TripCountV, Value *VectorTripCountV,
 
   IRBuilder<> Builder(State.CFG.PrevBB->getTerminator());
   // FIXME: Model VF * UF computation completely in VPlan.
-  VFxUF.setUnderlyingValue(
-      createStepForVF(Builder, TripCountV->getType(), State.VF, State.UF));
+  if (VF.getNumUsers()) {
+    Value *RuntimeVF =
+        createStepForVF(Builder, TripCountV->getType(), State.VF, 1);
+    VF.setUnderlyingValue(RuntimeVF);
+    VFxUF.setUnderlyingValue(
+        State.UF > 1
+            ? Builder.CreateMul(
+                  RuntimeVF, ConstantInt::get(TripCountV->getType(), State.UF))
----------------
fhahn wrote:

It works for both scalable and fixed vectors, in the later case the multiplies of constants will be folded, in the former we have a multiply instruction of RuntimeVF (which in turn is (vscale * VF)

https://github.com/llvm/llvm-project/pull/95305