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[IndVars] Improve code; use SCEVPatternMatch (NFC) #139533

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Merged
merged 2 commits into from
May 22, 2025
Merged

[IndVars] Improve code; use SCEVPatternMatch (NFC) #139533

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284b154
[IVSimplify] Improve code in isLoopCounter (NFC)
artagnon May 12, 2025
a0d368d
[IndVars] Use m_scev_AffineAddRec
artagnon May 22, 2025
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12 changes: 5 additions & 7 deletions llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionPatternMatch.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
Expand All @@ -53,7 +54,6 @@
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PatternMatch.h"
Expand All @@ -79,6 +79,7 @@

using namespace llvm;
using namespace PatternMatch;
using namespace SCEVPatternMatch;

#define DEBUG_TYPE "indvars"

Expand Down Expand Up @@ -806,12 +807,9 @@ static bool isLoopCounter(PHINode* Phi, Loop *L,
if (!SE->isSCEVable(Phi->getType()))
return false;

const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Phi));
if (!AR || AR->getLoop() != L || !AR->isAffine())
return false;

const SCEV *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE));
if (!Step || !Step->isOne())
const SCEV *S = SE->getSCEV(Phi);
if (!match(S, m_scev_AffineAddRec(m_SCEV(), m_scev_One())) ||
cast<SCEVAddRecExpr>(S)->getLoop() != L)
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Might make sense to have a m_scev_AffineAddRec variant that takes the Loop as an argument?

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Yeah I had some code for that lying around somewhere, let me see if I can find it again

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Will do in a follow-up, if @fhahn doesn't beat me to it.

return false;

int LatchIdx = Phi->getBasicBlockIndex(L->getLoopLatch());
Expand Down