[llvm] [LV] Add support for partial reductions without a binary op (PR #133922)

[Graham Hunter via llvm-commits]

================
@@ -296,34 +296,21 @@ bool VPRecipeBase::isScalarCast() const {
 InstructionCost
 VPPartialReductionRecipe::computeCost(ElementCount VF,
                                       VPCostContext &Ctx) const {
-  std::optional<unsigned> Opcode = std::nullopt;
-  VPValue *BinOp = getOperand(1);
+  std::optional<unsigned> Opcode;
+  VPValue *Op = getOperand(0);
+  VPRecipeBase *OpR = Op->getDefiningRecipe();
 
-  // If the partial reduction is predicated, a select will be operand 0 rather
-  // than the binary op
+  // If the partial reduction is predicated, a select will be operand 0
   using namespace llvm::VPlanPatternMatch;
-  if (match(getOperand(1), m_Select(m_VPValue(), m_VPValue(), m_VPValue())))
-    BinOp = BinOp->getDefiningRecipe()->getOperand(1);
-
-  // If BinOp is a negation, use the side effect of match to assign the actual
-  // binary operation to BinOp
-  match(BinOp, m_Binary<Instruction::Sub>(m_SpecificInt(0), m_VPValue(BinOp)));
-  VPRecipeBase *BinOpR = BinOp->getDefiningRecipe();
-
-  if (auto *WidenR = dyn_cast<VPWidenRecipe>(BinOpR))
-    Opcode = std::make_optional(WidenR->getOpcode());
-
-  VPRecipeBase *ExtAR = BinOpR->getOperand(0)->getDefiningRecipe();
-  VPRecipeBase *ExtBR = BinOpR->getOperand(1)->getDefiningRecipe();
+  if (match(getOperand(1), m_Select(m_VPValue(), m_VPValue(Op), m_VPValue()))) {
+    OpR = Op->getDefiningRecipe();
+  }
 
-  auto *PhiType = Ctx.Types.inferScalarType(getOperand(1));
-  auto *InputTypeA = Ctx.Types.inferScalarType(ExtAR ? ExtAR->getOperand(0)
-                                                     : BinOpR->getOperand(0));
-  auto *InputTypeB = Ctx.Types.inferScalarType(ExtBR ? ExtBR->getOperand(0)
-                                                     : BinOpR->getOperand(1));
+  Type *InputTypeA = nullptr, *InputTypeB = nullptr;
+  TTI::PartialReductionExtendKind ExtAType = TargetTransformInfo::PR_None,
----------------
huntergr-arm wrote:

```suggestion
  TTI::PartialReductionExtendKind ExtAType = TTI::PR_None,
```

https://github.com/llvm/llvm-project/pull/133922