[llvm-branch-commits] [llvm] [LV] Only create partial reductions when profitable. (PR #181706)

[Florian Hahn via llvm-branch-commits]

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@@ -4405,37 +4401,24 @@ tryToMatchAndCreateMulAccumulateReduction(VPReductionRecipe *Red,
               Ext0 ? Ctx.Types.inferScalarType(Ext0->getOperand(0)) : RedTy;
           InstructionCost MulAccCost;
 
-          if (Red->isPartialReduction()) {
-            Type *SrcTy2 =
-                Ext1 ? Ctx.Types.inferScalarType(Ext1->getOperand(0)) : nullptr;
-            // FIXME: Move partial reduction creation, costing and clamping
-            // here from LoopVectorize.cpp.
-            MulAccCost = Ctx.TTI.getPartialReductionCost(
-                Opcode, SrcTy, SrcTy2, RedTy, VF,
-                Ext0 ? TargetTransformInfo::getPartialReductionExtendKind(
-                           Ext0->getOpcode())
-                     : TargetTransformInfo::PR_None,
-                Ext1 ? TargetTransformInfo::getPartialReductionExtendKind(
-                           Ext1->getOpcode())
-                     : TargetTransformInfo::PR_None,
-                Mul->getOpcode(), CostKind,
-                RedTy->isFloatingPointTy()
-                    ? std::optional{Red->getFastMathFlags()}
-                    : std::nullopt);
-          } else {
-            // Only partial reductions support mixed or floating-point extends
-            // at the moment.
-            if (Ext0 && Ext1 &&
-                (Ext0->getOpcode() != Ext1->getOpcode() ||
-                 Ext0->getOpcode() == Instruction::CastOps::FPExt))
-              return false;
+          // For partial reductions, the decision has already been
+          // made at the point of transforming reductions -> partial
+          // reductions for a given plan, based on the cost-model.
+          if (Red->isPartialReduction())
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fhahn wrote:

should also be able to move up

https://github.com/llvm/llvm-project/pull/181706