[llvm] [VPlan] Remove no-op SCALAR-STEPS after unrolling. (PR #123655)

[Florian Hahn via llvm-commits]

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@@ -890,6 +890,17 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
     return;
   }
 
+  // VPScalarIVSteps can only be simplified after unrolling. VPScalarIVSteps for
+  // part 0 can be replaced by their start value, if only the first lane is
+  // demanded.
+  if (auto *Steps = dyn_cast<VPScalarIVStepsRecipe>(&R)) {
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fhahn wrote:

VPWidenEVL is gone now, so I removed the changes to VPlanPatternMatch from the patch again

https://github.com/llvm/llvm-project/pull/123655