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Restrict LDA to affine subscripts.

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llvm-svn: 77932
This commit is contained in:
Andreas Bolka 2009-08-03 01:03:48 +00:00
parent 9bbadad09d
commit 6fc741e683
2 changed files with 27 additions and 0 deletions
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9
include/llvm/Analysis/LoopDependenceAnalysis.h
View File

@ -67,6 +67,15 @@ class LoopDependenceAnalysis : public LoopPass {
/// created. The third argument is set to the pair found or created.
bool findOrInsertDependencePair(Value*, Value*, DependencePair*&);
/// isLoopInvariant - True if a given SCEV is invariant in all loops of the
/// loop-nest starting at the innermost loop L.
bool isLoopInvariant(const SCEV*) const;
/// isAffine - An SCEV is affine with respect to the loop-nest starting at
/// the innermost loop L if it is of the form A+B*X where A, B are invariant
/// in the loop-nest and X is a induction variable in the loop-nest.
bool isAffine(const SCEV*) const;
/// TODO: doc
DependenceResult analyseSubscript(const SCEV*, const SCEV*, Subscript*) const;
DependenceResult analysePair(DependencePair*) const;

18
lib/Analysis/LoopDependenceAnalysis.cpp
View File

@ -25,6 +25,7 @@
#include "llvm/Analysis/LoopDependenceAnalysis.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Instructions.h"
#include "llvm/Operator.h"
#include "llvm/Support/Allocator.h"
@ -123,6 +124,18 @@ bool LoopDependenceAnalysis::findOrInsertDependencePair(Value *A,
return false;
}
bool LoopDependenceAnalysis::isLoopInvariant(const SCEV *S) const {
for (const Loop *L = this->L; L != 0; L = L->getParentLoop())
if (!S->isLoopInvariant(L))
return false;
return true;
}
bool LoopDependenceAnalysis::isAffine(const SCEV *S) const {
const SCEVAddRecExpr *rec = dyn_cast<SCEVAddRecExpr>(S);
return isLoopInvariant(S) || (rec && rec->isAffine());
}
LoopDependenceAnalysis::DependenceResult
LoopDependenceAnalysis::analyseSubscript(const SCEV *A,
const SCEV *B,
@ -134,6 +147,11 @@ LoopDependenceAnalysis::analyseSubscript(const SCEV *A,
return Dependent;
}
if (!isAffine(A) || !isAffine(B)) {
DEBUG(errs() << " -> [?] not affine\n");
return Unknown;
}
// TODO: Implement ZIV/SIV/MIV testers.
DEBUG(errs() << " -> [?] cannot analyse subscript\n");