Refactor Code inside LoopVectorizer's function isInductionVariable

[karthikthecool]

Summary

Hi Adam, Renato,
I would like to reuse code inside isInductionVariable in one of my Pass.
This patch refactors the code and exposes function isInductionPHI. No functionality change.

Please let me know if this is good to commit.

Thanks and Regards
Karthik Bhat

[• deepa.saini]

test comment fr inline commenting

[karthikthecool]

Thanks Arnold. Committed as r233352.

include/llvm/Transforms/Utils/LoopUtils.h

bool promoteLoopAccessesToScalars(AliasSet &, SmallVectorImpl<BasicBlock*> &,
                                   LICMSafetyInfo *);
 
 /// \brief Computes safety information for a loop
 /// checks loop body & header for the possiblity of may throw
 /// exception, it takes LICMSafetyInfo and loop as argument.
 /// Updates safety information in LICMSafetyInfo argument.
 void computeLICMSafetyInfo(LICMSafetyInfo *, Loop *);
 
+/// \brief Checks if the give PHINode in a loop header is a induction variable.
+/// Returns true if this is an induction PHI along with the step value.
+bool isInductionPHI(PHINode *, ScalarEvolution *, ConstantInt *&);
 }
 
 #endif

lib/Transforms/Vectorize/LoopVectorize.cpp

 #include "llvm/Support/BranchProbability.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/VectorUtils.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
 #include <algorithm>
 #include <map>
 #include <tuple>
 
 using namespace llvm;
 using namespace llvm::PatternMatch;
 
 #define LV_NAME "loop-vectorize"
LoopVectorizationLegality::isReductionInstr(Instruction *I,
   case Instruction::Select:
     if (Kind != RK_IntegerMinMax &&
         (!HasFunNoNaNAttr || Kind != RK_FloatMinMax))
       return ReductionInstDesc(false, I);
     return isMinMaxSelectCmpPattern(I, Prev);
   }
 }
 
-LoopVectorizationLegality::InductionKind
-LoopVectorizationLegality::isInductionVariable(PHINode *Phi,
-                                               ConstantInt *&StepValue) {
+bool llvm::isInductionPHI(PHINode *Phi, ScalarEvolution *SE,
   Type *PhiTy = Phi->getType();
   // We only handle integer and pointer inductions variables.
   if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
-    return IK_NoInduction;
+    return false;
 
   // Check that the PHI is consecutive.
   const SCEV *PhiScev = SE->getSCEV(Phi);
   const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
   if (!AR) {
     DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
-    return IK_NoInduction;
+    return false;
   }
 
   const SCEV *Step = AR->getStepRecurrence(*SE);
   // Calculate the pointer stride and check if it is consecutive.
   const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
   if (!C)
-    return IK_NoInduction;
+    return false;
 
   ConstantInt *CV = C->getValue();
   if (PhiTy->isIntegerTy()) {
     StepValue = CV;
-    return IK_IntInduction;
+    return true;
   }
 
   assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
   Type *PointerElementType = PhiTy->getPointerElementType();
   // The pointer stride cannot be determined if the pointer element type is not
   // sized.
   if (!PointerElementType->isSized())
-    return IK_NoInduction;
+    return false;
 
   const DataLayout &DL = Phi->getModule()->getDataLayout();
   int64_t Size = static_cast<int64_t>(DL.getTypeAllocSize(PointerElementType));
   int64_t CVSize = CV->getSExtValue();
   if (CVSize % Size)
-    return IK_NoInduction;
+    return false;
   StepValue = ConstantInt::getSigned(CV->getType(), CVSize / Size);
+  return true;
+}
+
+LoopVectorizationLegality::InductionKind
+LoopVectorizationLegality::isInductionVariable(PHINode *Phi,
+                                               ConstantInt *&StepValue) {
+  if (!isInductionPHI(Phi, SE, StepValue))
+    return IK_NoInduction;
+
+  Type *PhiTy = Phi->getType();
+  // Found an Integer induction variable.
+  if (PhiTy->isIntegerTy())
+    return IK_IntInduction;
+  // Found an Pointer induction variable.
   return IK_PtrInduction;
 }
 
 bool LoopVectorizationLegality::isInductionVariable(const Value *V) {
   Value *In0 = const_cast<Value*>(V);
   PHINode *PN = dyn_cast_or_null<PHINode>(In0);
   if (!PN)
     return false;