[llvm] [LV] Bundle partial reductions inside VPExpressionRecipe (PR #147302)

[Sam Tebbs via llvm-commits]

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@@ -3520,16 +3532,29 @@ tryToMatchAndCreateMulAccumulateReduction(VPReductionRecipe *Red,
 
   // Clamp the range if using multiply-accumulate-reduction is profitable.
   auto IsMulAccValidAndClampRange =
-      [&](bool isZExt, VPWidenRecipe *Mul, VPWidenCastRecipe *Ext0,
-          VPWidenCastRecipe *Ext1, VPWidenCastRecipe *OuterExt) -> bool {
+      [&](VPWidenRecipe *Mul, VPWidenCastRecipe *Ext0, VPWidenCastRecipe *Ext1,
+          VPWidenCastRecipe *OuterExt) -> bool {
     return LoopVectorizationPlanner::getDecisionAndClampRange(
         [&](ElementCount VF) {
+          if (IsPartialReduction) {
+            // The VF ranges have already been clamped for a partial reduction
+            // and its existence confirms that it's valid, so we don't need to
+            // perform any cost checks or more clamping.
----------------
SamTebbs33 wrote:

Good idea, done.

https://github.com/llvm/llvm-project/pull/147302