Add newlines.

[oota-llvm.git] / lib / Analysis / LoopDependenceAnalysis.cpp

diff --git a/lib/Analysis/LoopDependenceAnalysis.cpp b/lib/Analysis/LoopDependenceAnalysis.cpp
index bf3978ec4e88fd453f0f480793ce9d9c50defb8c..32d22662c341586e2be6a5a51c8d9a37e17da650 100644 (file)
--- a/lib/Analysis/LoopDependenceAnalysis.cpp
+++ b/lib/Analysis/LoopDependenceAnalysis.cpp
@@ -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"
@@ -92,7 +93,7 @@ static AliasAnalysis::AliasResult UnderlyingObjectsAlias(AliasAnalysis *AA,
 }
 
 static inline const SCEV *GetZeroSCEV(ScalarEvolution *SE) {
-  return SE->getConstant(Type::Int32Ty, 0L);
+  return SE->getConstant(Type::getInt32Ty(SE->getContext()), 0L);
 }
 
 //===----------------------------------------------------------------------===//
@@ -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 {
@@ -136,6 +144,39 @@ bool LoopDependenceAnalysis::isAffine(const SCEV *S) const {
   return isLoopInvariant(S) || (rec && rec->isAffine());
 }
 
+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,
+                                   Subscript *S) const {
+  assert(isZIVPair(A, B) && "Attempted to ZIV-test non-ZIV SCEVs!");
+  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,
@@ -152,10 +193,13 @@ LoopDependenceAnalysis::analyseSubscript(const SCEV *A,
     return Unknown;
   }
 
-  // TODO: Implement ZIV/SIV/MIV testers.
+  if (isZIVPair(A, B))
+    return analyseZIV(A, B, S);
+
+  if (isSIVPair(A, B))
+    return analyseSIV(A, B, S);
 
-  DEBUG(errs() << "  -> [?] cannot analyse subscript\n");
-  return Unknown;
+  return analyseMIV(A, B, S);
 }
 
 LoopDependenceAnalysis::DependenceResult
@@ -195,28 +239,44 @@ LoopDependenceAnalysis::analysePair(DependencePair *P) const {
 
   // FIXME: Is filtering coupled subscripts necessary?
 
-  // Analyse indices pairwise (FIXME: use GetGEPOperands from BasicAA), adding
+  // Collect GEP operand pairs (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) {
+  typedef SmallVector<std::pair<const SCEV*, const SCEV*>, 4> GEPOpdPairsTy;
+  GEPOpdPairsTy opds;
+  for(GEPOperator::const_op_iterator aIdx = aGEP->idx_begin(),
+                                     aEnd = aGEP->idx_end(),
+                                     bIdx = bGEP->idx_begin(),
+                                     bEnd = bGEP->idx_end();
+      aIdx != aEnd && bIdx != bEnd;
+      aIdx += (aIdx != aEnd), bIdx += (bIdx != bEnd)) {
     const SCEV* aSCEV = (aIdx != aEnd) ? SE->getSCEV(*aIdx) : GetZeroSCEV(SE);
     const SCEV* bSCEV = (bIdx != bEnd) ? SE->getSCEV(*bIdx) : GetZeroSCEV(SE);
+    opds.push_back(std::make_pair(aSCEV, bSCEV));
+  }
+
+  if (!opds.empty() && opds[0].first != opds[0].second) {
+    // We cannot (yet) handle arbitrary GEP pointer offsets. By limiting
+    //
+    // TODO: this could be relaxed by adding the size of the underlying object
+    // to the first subscript. If we have e.g. (GEP x,0,i; GEP x,2,-i) and we
+    // know that x is a [100 x i8]*, we could modify the first subscript to be
+    // (i, 200-i) instead of (i, -i).
+    return Unknown;
+  }
+
+  // Now analyse the collected operand pairs (skipping the GEP ptr offsets).
+  for (GEPOpdPairsTy::const_iterator i = opds.begin() + 1, end = opds.end();
+       i != end; ++i) {
     Subscript subscript;
-    DependenceResult result = analyseSubscript(aSCEV, bSCEV, &subscript);
+    DependenceResult result = analyseSubscript(i->first, i->second, &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.
+  // We successfully analysed all subscripts but failed to prove independence.
   return Dependent;
 }
 
@@ -290,8 +350,3 @@ void LoopDependenceAnalysis::print(raw_ostream &OS, const Module*) const {
   // TODO: doc why const_cast is safe
   PrintLoopInfo(OS, const_cast<LoopDependenceAnalysis*>(this), this->L);
 }
-
-void LoopDependenceAnalysis::print(std::ostream &OS, const Module *M) const {
-  raw_os_ostream os(OS);
-  print(os, M);
-}