Skeleton for pairwise subscript testing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77437 91177308-0d34-0410-b5e6-96231b3b80d8
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 @@
bObj, AA->getTypeStoreSize(bObj->getType()));
}
+static inline const SCEV *GetZeroSCEV(ScalarEvolution *SE) {
+ return SE->getConstant(Type::Int32Ty, 0L);
+}
+
//===----------------------------------------------------------------------===//
// Dependence Testing
//===----------------------------------------------------------------------===//
@@ -117,6 +124,13 @@
}
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 @@
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) {