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authorAndreas Bolka <a@bolka.at>2009-07-29 05:35:53 +0000
committerAndreas Bolka <a@bolka.at>2009-07-29 05:35:53 +0000
commit15f72dbf972f056b1685786e5118148fb528f233 (patch)
tree700e798597427d154003045fa2d7ee08c3eb2ccf
parent45ce89ba080f4be72e4e49367567114800f6b3c5 (diff)
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Skeleton for pairwise subscript testing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77437 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--include/llvm/Analysis/LoopDependenceAnalysis.h16
-rw-r--r--lib/Analysis/LoopDependenceAnalysis.cpp48
2 files changed, 56 insertions, 8 deletions
diff --git a/include/llvm/Analysis/LoopDependenceAnalysis.h b/include/llvm/Analysis/LoopDependenceAnalysis.h
index 3eab665..56a6b6e 100644
--- a/include/llvm/Analysis/LoopDependenceAnalysis.h
+++ b/include/llvm/Analysis/LoopDependenceAnalysis.h
@@ -21,6 +21,7 @@
#define LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H
#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Support/Allocator.h"
#include <iosfwd>
@@ -30,6 +31,7 @@ namespace llvm {
class AliasAnalysis;
class AnalysisUsage;
class ScalarEvolution;
+class SCEV;
class Value;
class raw_ostream;
@@ -43,17 +45,21 @@ class LoopDependenceAnalysis : public LoopPass {
/// TODO: doc
enum DependenceResult { Independent = 0, Dependent = 1, Unknown = 2 };
+ /// TODO: doc
+ struct Subscript {
+ /// TODO: Add distance, direction, breaking conditions, ...
+ };
+
/// DependencePair - Represents a data dependence relation between to memory
/// reference instructions.
- ///
- /// TODO: add subscripts vector
struct DependencePair : public FastFoldingSetNode {
Value *A;
Value *B;
DependenceResult Result;
+ SmallVector<Subscript, 4> Subscripts;
DependencePair(const FoldingSetNodeID &ID, Value *a, Value *b) :
- FastFoldingSetNode(ID), A(a), B(b), Result(Unknown) {}
+ FastFoldingSetNode(ID), A(a), B(b), Result(Unknown), Subscripts() {}
};
/// findOrInsertDependencePair - Return true if a DependencePair for the
@@ -62,7 +68,8 @@ class LoopDependenceAnalysis : public LoopPass {
bool findOrInsertDependencePair(Value*, Value*, DependencePair*&);
/// TODO: doc
- DependenceResult analysePair(DependencePair *P) const;
+ DependenceResult analyseSubscript(const SCEV*, const SCEV*, Subscript*) const;
+ DependenceResult analysePair(DependencePair*) const;
public:
static char ID; // Class identification, replacement for typeinfo
@@ -88,7 +95,6 @@ private:
BumpPtrAllocator PairAllocator;
}; // class LoopDependenceAnalysis
-
// createLoopDependenceAnalysisPass - This creates an instance of the
// LoopDependenceAnalysis pass.
//
diff --git a/lib/Analysis/LoopDependenceAnalysis.cpp b/lib/Analysis/LoopDependenceAnalysis.cpp
index 78c3975..51f6c3a 100644
--- a/lib/Analysis/LoopDependenceAnalysis.cpp
+++ b/lib/Analysis/LoopDependenceAnalysis.cpp
@@ -15,6 +15,8 @@
//
// TODO: adapt as implementation progresses.
//
+// TODO: document lingo (pair, subscript, index)
+//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lda"
@@ -24,6 +26,7 @@
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Instructions.h"
+#include "llvm/Operator.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@@ -87,6 +90,10 @@ static AliasAnalysis::AliasResult UnderlyingObjectsAlias(AliasAnalysis *AA,
bObj, AA->getTypeStoreSize(bObj->getType()));
}
+static inline const SCEV *GetZeroSCEV(ScalarEvolution *SE) {
+ return SE->getConstant(Type::Int32Ty, 0L);
+}
+
//===----------------------------------------------------------------------===//
// Dependence Testing
//===----------------------------------------------------------------------===//
@@ -117,6 +124,13 @@ bool LoopDependenceAnalysis::findOrInsertDependencePair(Value *A,
}
LoopDependenceAnalysis::DependenceResult
+LoopDependenceAnalysis::analyseSubscript(const SCEV *A,
+ const SCEV *B,
+ Subscript *S) const {
+ return Unknown; // TODO: Implement.
+}
+
+LoopDependenceAnalysis::DependenceResult
LoopDependenceAnalysis::analysePair(DependencePair *P) const {
DEBUG(errs() << "Analysing:\n" << *P->A << "\n" << *P->B << "\n");
@@ -145,9 +159,37 @@ LoopDependenceAnalysis::analysePair(DependencePair *P) const {
break; // The underlying objects alias, test accesses for dependence.
}
- // We failed to analyse this pair to get a more specific answer.
- DEBUG(errs() << "---> [?] cannot analyse\n");
- return Unknown;
+ const GEPOperator *aGEP = dyn_cast<GEPOperator>(aPtr);
+ const GEPOperator *bGEP = dyn_cast<GEPOperator>(bPtr);
+
+ if (!aGEP || !bGEP)
+ return Unknown;
+
+ // FIXME: Is filtering coupled subscripts necessary?
+
+ // Analyse indices pairwise (FIXME: use GetGEPOperands from BasicAA), adding
+ // trailing zeroes to the smaller GEP, if needed.
+ GEPOperator::const_op_iterator aIdx = aGEP->idx_begin(),
+ aEnd = aGEP->idx_end(),
+ bIdx = bGEP->idx_begin(),
+ bEnd = bGEP->idx_end();
+ while (aIdx != aEnd && bIdx != bEnd) {
+ const SCEV* aSCEV = (aIdx != aEnd) ? SE->getSCEV(*aIdx) : GetZeroSCEV(SE);
+ const SCEV* bSCEV = (bIdx != bEnd) ? SE->getSCEV(*bIdx) : GetZeroSCEV(SE);
+ Subscript subscript;
+ DependenceResult result = analyseSubscript(aSCEV, bSCEV, &subscript);
+ if (result != Dependent) {
+ // We either proved independence or failed to analyse this subscript.
+ // Further subscripts will not improve the situation, so abort early.
+ return result;
+ }
+ P->Subscripts.push_back(subscript);
+ if (aIdx != aEnd) ++aIdx;
+ if (bIdx != bEnd) ++bIdx;
+ }
+ // Either there were no subscripts or all subscripts were analysed to be
+ // dependent; in both cases we know the accesses are dependent.
+ return Dependent;
}
bool LoopDependenceAnalysis::depends(Value *A, Value *B) {