[IVDesc] Address review

Author: artagnon

llvm/include/llvm/Analysis/IVDescriptors.h

@@ -401,7 +401,7 @@ class InductionDescriptor {
   InductionKind getKind() const { return IK; }
   const SCEV *getStep() const { return Step; }
   BinaryOperator *getInductionBinOp() const { return InductionBinOp; }
-  LLVM_ABI const APInt *getStepValue() const;
+  LLVM_ABI ConstantInt *getConstIntStepValue() const;
 
   /// Returns true if \p Phi is an induction in the loop \p L. If \p Phi is an
   /// induction, the induction descriptor \p D will contain the data describing

llvm/lib/Analysis/IVDescriptors.cpp

@@ -1382,7 +1382,7 @@ InductionDescriptor::InductionDescriptor(Value *Start, InductionKind K,
          "StartValue is not an integer for integer induction");
 
   // Check the Step Value. It should be non-zero integer value.
-  assert((!getStepValue() || !getStepValue()->isZero()) &&
+  assert((!getConstIntStepValue() || !getConstIntStepValue()->isZero()) &&
          "Step value is zero");
 
   assert((IK == IK_FpInduction || Step->getType()->isIntegerTy()) &&
@@ -1400,11 +1400,10 @@ InductionDescriptor::InductionDescriptor(Value *Start, InductionKind K,
     llvm::append_range(RedundantCasts, *Casts);
 }
 
-const APInt *InductionDescriptor::getStepValue() const {
-  const APInt *StepC;
-  if (!match(Step, m_scev_APInt(StepC)))
-    return nullptr;
-  return StepC;
+ConstantInt *InductionDescriptor::getConstIntStepValue() const {
+  if (auto *C = dyn_cast<SCEVConstant>(Step))
+    return dyn_cast<ConstantInt>(C->getValue());
+  return nullptr;
 }
 
 bool InductionDescriptor::isFPInductionPHI(PHINode *Phi, const Loop *TheLoop,
@@ -1621,6 +1620,10 @@ bool InductionDescriptor::isInductionPHI(
   // Check that the PHI is consecutive.
   const SCEV *PhiScev = Expr ? Expr : SE->getSCEV(Phi);
   const SCEV *Step;
+
+  // FIXME: We are currently matching the specific loop TheLoop; if it doesn't
+  // match, we should treat it as a uniform. Unfortunately, we don't currently
+  // know how to handled uniform PHIs.
   if (!match(PhiScev, m_scev_AffineAddRec(m_SCEV(), m_SCEV(Step),
                                           m_SpecificLoop(TheLoop)))) {
     LLVM_DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");

llvm/lib/Analysis/LoopInfo.cpp

@@ -421,7 +421,7 @@ bool Loop::isCanonical(ScalarEvolution &SE) const {
   if (IndDesc.getInductionOpcode() != Instruction::Add)
     return false;
 
-  const APInt *Step = IndDesc.getStepValue();
+  ConstantInt *Step = IndDesc.getConstIntStepValue();
   if (!Step || !Step->isOne())
     return false;
 

llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp

@@ -704,7 +704,7 @@ void LoopVectorizationLegality::addInductionPhi(
 
   // Int inductions are special because we only allow one IV.
   if (ID.getKind() == InductionDescriptor::IK_IntInduction &&
-      ID.getStepValue() && ID.getStepValue()->isOne() &&
+      ID.getConstIntStepValue() && ID.getConstIntStepValue()->isOne() &&
       isa<Constant>(ID.getStartValue()) &&
       cast<Constant>(ID.getStartValue())->isNullValue()) {
 
@@ -889,7 +889,7 @@ bool LoopVectorizationLegality::canVectorizeInstr(Instruction &I) {
           if (AllowStridedPointerIVs)
             return false;
           return ID.getKind() == InductionDescriptor::IK_PtrInduction &&
-                 ID.getStepValue() == nullptr;
+                 ID.getConstIntStepValue() == nullptr;
         };
 
     // TODO: Instead of recording the AllowedExit, it would be good to