[Analysis] Pass RecurrenceDescriptor as const reference. NFCI.

We were passing the RecurrenceDescriptor by value to most of the reduction analysis methods, despite it being rather bulky with TrackingVH members (that can be costly to copy). In all these cases we're only using the RecurrenceDescriptor for rather basic purposes (access to types/kinds etc.).

Differential Revision: https://reviews.llvm.org/D104029

3 files changed, 12 insertions, 11 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 95ae7db..f78ddd0 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1000,7 +1000,8 @@ Value *llvm::createSimpleTargetReduction(IRBuilderBase &Builder,
 
 Value *llvm::createTargetReduction(IRBuilderBase &B,
                                    const TargetTransformInfo *TTI,
-                                   RecurrenceDescriptor &Desc, Value *Src) {
+                                   const RecurrenceDescriptor &Desc,
+                                   Value *Src) {
   // TODO: Support in-order reductions based on the recurrence descriptor.
   // All ops in the reduction inherit fast-math-flags from the recurrence
   // descriptor.
@@ -1010,8 +1011,8 @@ Value *llvm::createTargetReduction(IRBuilderBase &B,
 }
 
 Value *llvm::createOrderedReduction(IRBuilderBase &B,
-                                    RecurrenceDescriptor &Desc, Value *Src,
-                                    Value *Start) {
+                                    const RecurrenceDescriptor &Desc,
+                                    Value *Src, Value *Start) {
   assert(Desc.getRecurrenceKind() == RecurKind::FAdd &&
          "Unexpected reduction kind");
   assert(Src->getType()->isVectorTy() && "Expected a vector type");
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 1c08e77..e97620e 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -921,7 +921,7 @@ bool LoopVectorizationLegality::canVectorizeFPMath(
   // have the isOrdered flag set, which indicates that we can move the
   // reduction operations in-loop.
   return (all_of(getReductionVars(), [&](auto &Reduction) -> bool {
-    RecurrenceDescriptor RdxDesc = Reduction.second;
+    const RecurrenceDescriptor &RdxDesc = Reduction.second;
     return !RdxDesc.hasExactFPMath() || RdxDesc.isOrdered();
   }));
 }
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index bc745c0..06b415e 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -598,7 +598,7 @@ protected:
   void fixReduction(VPWidenPHIRecipe *Phi, VPTransformState &State);
 
   /// Clear NSW/NUW flags from reduction instructions if necessary.
-  void clearReductionWrapFlags(RecurrenceDescriptor &RdxDesc,
+  void clearReductionWrapFlags(const RecurrenceDescriptor &RdxDesc,
                                VPTransformState &State);
 
   /// Fixup the LCSSA phi nodes in the unique exit block.  This simply
@@ -1310,7 +1310,7 @@ public:
   /// RdxDesc. This is true if the -enable-strict-reductions flag is passed,
   /// the IsOrdered flag of RdxDesc is set and we do not allow reordering
   /// of FP operations.
-  bool useOrderedReductions(RecurrenceDescriptor &RdxDesc) {
+  bool useOrderedReductions(const RecurrenceDescriptor &RdxDesc) {
     return EnableStrictReductions && !Hints->allowReordering() &&
            RdxDesc.isOrdered();
   }
@@ -1515,7 +1515,7 @@ public:
   /// variables found for the given VF.
   bool canVectorizeReductions(ElementCount VF) {
     return (all_of(Legal->getReductionVars(), [&](auto &Reduction) -> bool {
-      RecurrenceDescriptor RdxDesc = Reduction.second;
+      const RecurrenceDescriptor &RdxDesc = Reduction.second;
       return TTI.isLegalToVectorizeReduction(RdxDesc, VF);
     }));
   }
@@ -4331,7 +4331,7 @@ void InnerLoopVectorizer::fixReduction(VPWidenPHIRecipe *PhiR,
   // Get it's reduction variable descriptor.
   assert(Legal->isReductionVariable(OrigPhi) &&
          "Unable to find the reduction variable");
-  RecurrenceDescriptor RdxDesc = *PhiR->getRecurrenceDescriptor();
+  const RecurrenceDescriptor &RdxDesc = *PhiR->getRecurrenceDescriptor();
 
   RecurKind RK = RdxDesc.getRecurrenceKind();
   TrackingVH<Value> ReductionStartValue = RdxDesc.getRecurrenceStartValue();
@@ -4512,7 +4512,7 @@ void InnerLoopVectorizer::fixReduction(VPWidenPHIRecipe *PhiR,
   OrigPhi->setIncomingValue(IncomingEdgeBlockIdx, LoopExitInst);
 }
 
-void InnerLoopVectorizer::clearReductionWrapFlags(RecurrenceDescriptor &RdxDesc,
+void InnerLoopVectorizer::clearReductionWrapFlags(const RecurrenceDescriptor &RdxDesc,
                                                   VPTransformState &State) {
   RecurKind RK = RdxDesc.getRecurrenceKind();
   if (RK != RecurKind::Add && RK != RecurKind::Mul)
@@ -6273,7 +6273,7 @@ LoopVectorizationCostModel::getSmallestAndWidestTypes() {
       if (auto *PN = dyn_cast<PHINode>(&I)) {
         if (!Legal->isReductionVariable(PN))
           continue;
-        RecurrenceDescriptor RdxDesc = Legal->getReductionVars()[PN];
+        const RecurrenceDescriptor &RdxDesc = Legal->getReductionVars()[PN];
         if (PreferInLoopReductions || useOrderedReductions(RdxDesc) ||
             TTI.preferInLoopReduction(RdxDesc.getOpcode(),
                                       RdxDesc.getRecurrenceType(),
@@ -7173,7 +7173,7 @@ InstructionCost LoopVectorizationCostModel::getReductionPatternCost(
   while (!isa<PHINode>(ReductionPhi))
     ReductionPhi = InLoopReductionImmediateChains[ReductionPhi];
 
-  RecurrenceDescriptor RdxDesc =
+  const RecurrenceDescriptor &RdxDesc =
       Legal->getReductionVars()[cast<PHINode>(ReductionPhi)];
   InstructionCost BaseCost = TTI.getArithmeticReductionCost(
       RdxDesc.getOpcode(), VectorTy, false, CostKind);