[llvm] [LoopVectorizer] Add support for partial reductions (PR #92418)

[Sam Tebbs via llvm-commits]

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@@ -111,20 +138,40 @@ class VPRecipeBuilder {
   VPHistogramRecipe *tryToWidenHistogram(const HistogramInfo *HI,
                                          ArrayRef<VPValue *> Operands);
 
+  std::optional<PartialReductionChain>
+  getScaledReduction(PHINode *PHI, const RecurrenceDescriptor &Rdx,
+                     VFRange &Range);
+
 public:
   VPRecipeBuilder(VPlan &Plan, Loop *OrigLoop, const TargetLibraryInfo *TLI,
+                  const TargetTransformInfo *TTI,
                   LoopVectorizationLegality *Legal,
                   LoopVectorizationCostModel &CM,
                   PredicatedScalarEvolution &PSE, VPBuilder &Builder)
-      : Plan(Plan), OrigLoop(OrigLoop), TLI(TLI), Legal(Legal), CM(CM),
-        PSE(PSE), Builder(Builder) {}
+      : Plan(Plan), OrigLoop(OrigLoop), TLI(TLI), TTI(TTI), Legal(Legal),
+        CM(CM), PSE(PSE), Builder(Builder) {}
+
+  std::optional<PartialReductionChain>
+  getScaledReductionForInstr(const Instruction *ExitInst) {
+    auto It = ScaledReductionExitInstrs.find(ExitInst);
+    return It == ScaledReductionExitInstrs.end()
+               ? std::nullopt
+               : std::make_optional(It->second);
+  }
+
+  void collectScaledReductions(VFRange &Range);
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SamTebbs33 wrote:

Done.

https://github.com/llvm/llvm-project/pull/92418