Fix how DependenceAnalysis calls delinearization

Fix how DependenceAnalysis calls delinearization, mirroring what is done in
Delinearization.cpp (mostly by making sure to call getSCEVAtScope before
delinearizing, and by removing the unnecessary 'Pairs == 1' check).

Patch by Vaivaswatha Nagaraj!

llvm-svn: 245408

3 files changed, 43 insertions, 27 deletions

diff --git a/llvm/include/llvm/Analysis/DependenceAnalysis.h b/llvm/include/llvm/Analysis/DependenceAnalysis.h
index b05a72ebb6f..9cd2a1700c6 100644
--- a/llvm/include/llvm/Analysis/DependenceAnalysis.h
+++ b/llvm/include/llvm/Analysis/DependenceAnalysis.h
@@ -926,9 +926,8 @@ namespace llvm {
     void updateDirection(Dependence::DVEntry &Level,
                          const Constraint &CurConstraint) const;
 
-    bool tryDelinearize(const SCEV *SrcSCEV, const SCEV *DstSCEV,
-                        SmallVectorImpl<Subscript> &Pair,
-                        const SCEV *ElementSize);
+    bool tryDelinearize(Instruction *Src, Instruction *Dst,
+                        SmallVectorImpl<Subscript> &Pair);
 
   public:
     static char ID; // Class identification, replacement for typeinfo
diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 0e6f222e52e..5add828770f 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -3245,20 +3245,36 @@ void DependenceAnalysis::updateDirection(Dependence::DVEntry &Level,
 /// source and destination array references are recurrences on a nested loop,
 /// this function flattens the nested recurrences into separate recurrences
 /// for each loop level.
-bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
-                                        const SCEV *DstSCEV,
-                                        SmallVectorImpl<Subscript> &Pair,
-                                        const SCEV *ElementSize) {
+bool DependenceAnalysis::tryDelinearize(Instruction *Src,
+                                        Instruction *Dst,
+                                        SmallVectorImpl<Subscript> &Pair)
+{
+  Value *SrcPtr = getPointerOperand(Src);
+  Value *DstPtr = getPointerOperand(Dst);
+
+  Loop *SrcLoop = LI->getLoopFor(Src->getParent());
+  Loop *DstLoop = LI->getLoopFor(Dst->getParent());
+
+  // Below code mimics the code in Delinearization.cpp
+  const SCEV *SrcAccessFn =
+    SE->getSCEVAtScope(SrcPtr, SrcLoop);
+  const SCEV *DstAccessFn =
+    SE->getSCEVAtScope(DstPtr, DstLoop);
+
   const SCEVUnknown *SrcBase =
-      dyn_cast<SCEVUnknown>(SE->getPointerBase(SrcSCEV));
+      dyn_cast<SCEVUnknown>(SE->getPointerBase(SrcAccessFn));
   const SCEVUnknown *DstBase =
-      dyn_cast<SCEVUnknown>(SE->getPointerBase(DstSCEV));
+      dyn_cast<SCEVUnknown>(SE->getPointerBase(DstAccessFn));
 
   if (!SrcBase || !DstBase || SrcBase != DstBase)
     return false;
 
-  SrcSCEV = SE->getMinusSCEV(SrcSCEV, SrcBase);
-  DstSCEV = SE->getMinusSCEV(DstSCEV, DstBase);
+  const SCEV *ElementSize = SE->getElementSize(Src);
+  if (ElementSize != SE->getElementSize(Dst))
+    return false;
+
+  const SCEV *SrcSCEV = SE->getMinusSCEV(SrcAccessFn, SrcBase);
+  const SCEV *DstSCEV = SE->getMinusSCEV(DstAccessFn, DstBase);
 
   const SCEVAddRecExpr *SrcAR = dyn_cast<SCEVAddRecExpr>(SrcSCEV);
   const SCEVAddRecExpr *DstAR = dyn_cast<SCEVAddRecExpr>(DstSCEV);
@@ -3331,7 +3347,6 @@ static void dumpSmallBitVector(SmallBitVector &BV) {
 }
 #endif
 
-
 // depends -
 // Returns NULL if there is no dependence.
 // Otherwise, return a Dependence with as many details as possible.
@@ -3426,10 +3441,11 @@ DependenceAnalysis::depends(Instruction *Src, Instruction *Dst,
     Pair[0].Dst = DstSCEV;
   }
 
-  if (Delinearize && Pairs == 1 && CommonLevels > 1 &&
-      tryDelinearize(Pair[0].Src, Pair[0].Dst, Pair, SE->getElementSize(Src))) {
-    DEBUG(dbgs() << "    delinerized GEP\n");
-    Pairs = Pair.size();
+  if (Delinearize && CommonLevels > 1) {
+    if (tryDelinearize(Src, Dst, Pair)) {
+      DEBUG(dbgs() << "    delinerized GEP\n");
+      Pairs = Pair.size();
+    }
   }
 
   for (unsigned P = 0; P < Pairs; ++P) {
@@ -3851,10 +3867,11 @@ const  SCEV *DependenceAnalysis::getSplitIteration(const Dependence &Dep,
     Pair[0].Dst = DstSCEV;
   }
 
-  if (Delinearize && Pairs == 1 && CommonLevels > 1 &&
-      tryDelinearize(Pair[0].Src, Pair[0].Dst, Pair, SE->getElementSize(Src))) {
-    DEBUG(dbgs() << "    delinerized GEP\n");
-    Pairs = Pair.size();
+  if (Delinearize && CommonLevels > 1) {
+    if (tryDelinearize(Src, Dst, Pair)) {
+      DEBUG(dbgs() << "    delinerized GEP\n");
+      Pairs = Pair.size();
+    }
   }
 
   for (unsigned P = 0; P < Pairs; ++P) {
diff --git a/llvm/test/Analysis/DependenceAnalysis/GCD.ll b/llvm/test/Analysis/DependenceAnalysis/GCD.ll
index 81d05a10cf1..f9749d51bb3 100644
--- a/llvm/test/Analysis/DependenceAnalysis/GCD.ll
+++ b/llvm/test/Analysis/DependenceAnalysis/GCD.ll
@@ -269,10 +269,10 @@ entry:
 ; CHECK: da analyze - none!
 
 ; DELIN: 'Dependence Analysis' for function 'gcd4'
-; DELIN: da analyze - output [* *]!
+; DELIN: da analyze - none!
 ; DELIN: da analyze - none!
 ; DELIN: da analyze - confused!
-; DELIN: da analyze - input [* *]!
+; DELIN: da analyze - none!
 ; DELIN: da analyze - confused!
 ; DELIN: da analyze - none!
 
@@ -339,10 +339,10 @@ entry:
 ; CHECK: da analyze - none!
 
 ; DELIN: 'Dependence Analysis' for function 'gcd5'
-; DELIN: da analyze - output [* *]!
-; DELIN: da analyze - flow [<> *]!
+; DELIN: da analyze - none!
+; DELIN: da analyze - flow [> *]!
 ; DELIN: da analyze - confused!
-; DELIN: da analyze - input [* *]!
+; DELIN: da analyze - none!
 ; DELIN: da analyze - confused!
 ; DELIN: da analyze - none!
 
@@ -410,10 +410,10 @@ entry:
 ; CHECK: da analyze - output [* *]!
 
 ; DELIN: 'Dependence Analysis' for function 'gcd6'
-; DELIN: da analyze - output [* *]!
+; DELIN: da analyze - none!
 ; DELIN: da analyze - none!
 ; DELIN: da analyze - confused!
-; DELIN: da analyze - input [* *]!
+; DELIN: da analyze - none!
 ; DELIN: da analyze - confused!
 ; DELIN: da analyze - output [* *]!