[llvm] [LV] Optimize VPWidenIntOrFpInductionRecipe for known TC (PR #118828)

[David Sherwood via llvm-commits]

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@@ -661,14 +661,16 @@ static void recursivelyDeleteDeadRecipes(VPValue *V) {
   }
 }
 
-void VPlanTransforms::optimizeForTCAndVF(VPlan &Plan, unsigned TC,
-                                         ElementCount BestVF) {
+void VPlanTransforms::optimizeForTCAndVFAndUF(VPlan &Plan, unsigned TC,
+                                              ElementCount BestVF,
+                                              unsigned BestUF) {
   assert(Plan.hasVF(BestVF) && "BestVF is not available in Plan");
+  assert(Plan.hasUF(BestUF) && "BestUF is not available in Plan");
   if (!TC || !BestVF.isFixed())
     return;
 
-  // Calculate the widest type required for known TC and VF.
-  uint64_t Width = BestVF.getKnownMinValue();
+  // Calculate the widest type required for known TC, VF and UF.
+  uint64_t Width = BestVF.getKnownMinValue() * BestUF;
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david-arm wrote:

After making this change I didn't see any corresponding change in the tests, which looks we have a missing test case. Is it possible to create a very simple test that is affected by this change? For example, if you have a known trip count of 50 and use `-force-vector-width=64 -force-vector-interleave=8` then the max value will be 511 and will require an i16 type. That's still better than an i64 type though!

https://github.com/llvm/llvm-project/pull/118828