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SIV/MIV classification for LDA.

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LoopDependenceAnalysis::getLoops is currently O(N*M) for a loop-nest of
depth N and a compound SCEV of M atomic SCEVs. As both N and M will
typically be very small, this should not be a problem. If it turns out
to be one, rewriting getLoops as SCEVVisitor will reduce complexity to
O(M).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78394 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andreas Bolka
2009-08-07 18:23:41 +00:00
parent 1c5a28706d
commit 699db99c1a
2 changed files with 43 additions and 6 deletions
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lib/Analysis/LoopDependenceAnalysis.cpp
+35 -6
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@@ -20,6 +20,7 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lda"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopDependenceAnalysis.h"
@@ -124,11 +125,18 @@ bool LoopDependenceAnalysis::findOrInsertDependencePair(Value *A,
return false;
}
bool LoopDependenceAnalysis::isLoopInvariant(const SCEV *S) const {
void LoopDependenceAnalysis::getLoops(const SCEV *S,
DenseSet<const Loop*>* Loops) const {
// Refactor this into an SCEVVisitor, if efficiency becomes a concern.
for (const Loop *L = this->L; L != 0; L = L->getParentLoop())
if (!S->isLoopInvariant(L))
return false;
return true;
Loops->insert(L);
}
bool LoopDependenceAnalysis::isLoopInvariant(const SCEV *S) const {
DenseSet<const Loop*> loops;
getLoops(S, &loops);
return loops.empty();
}
bool LoopDependenceAnalysis::isAffine(const SCEV *S) const {
@@ -140,6 +148,13 @@ bool LoopDependenceAnalysis::isZIVPair(const SCEV *A, const SCEV *B) const {
return isLoopInvariant(A) && isLoopInvariant(B);
}
bool LoopDependenceAnalysis::isSIVPair(const SCEV *A, const SCEV *B) const {
DenseSet<const Loop*> loops;
getLoops(A, &loops);
getLoops(B, &loops);
return loops.size() == 1;
}
LoopDependenceAnalysis::DependenceResult
LoopDependenceAnalysis::analyseZIV(const SCEV *A,
const SCEV *B,
@@ -148,6 +163,20 @@ LoopDependenceAnalysis::analyseZIV(const SCEV *A,
return A == B ? Dependent : Independent;
}
LoopDependenceAnalysis::DependenceResult
LoopDependenceAnalysis::analyseSIV(const SCEV *A,
const SCEV *B,
Subscript *S) const {
return Unknown; // TODO: Implement.
}
LoopDependenceAnalysis::DependenceResult
LoopDependenceAnalysis::analyseMIV(const SCEV *A,
const SCEV *B,
Subscript *S) const {
return Unknown; // TODO: Implement.
}
LoopDependenceAnalysis::DependenceResult
LoopDependenceAnalysis::analyseSubscript(const SCEV *A,
const SCEV *B,
@@ -167,10 +196,10 @@ LoopDependenceAnalysis::analyseSubscript(const SCEV *A,
if (isZIVPair(A, B))
return analyseZIV(A, B, S);
// TODO: Implement SIV/MIV testers.
if (isSIVPair(A, B))
return analyseSIV(A, B, S);
DEBUG(errs() << " -> [?] cannot analyse subscript\n");
return Unknown;
return analyseMIV(A, B, S);
}
LoopDependenceAnalysis::DependenceResult