remove BasePointer before delinearizing

No functional change is intended: instead of relying on the delinearization to
come up with the base pointer as a remainder of the divisions in the
delinearization, we just compute it from the array access and use that value.
We substract the base pointer from the SCEV to be delinearized and that
simplifies the work of the delinearizer.

llvm-svn: 209692

1 files changed, 13 insertions, 8 deletions

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 33cb20685c0..d0784f1e678 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -3184,6 +3184,17 @@ bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
                                         const SCEV *DstSCEV,
                                         SmallVectorImpl<Subscript> &Pair,
                                         const SCEV *ElementSize) const {
+  const SCEVUnknown *SrcBase =
+      dyn_cast<SCEVUnknown>(SE->getPointerBase(SrcSCEV));
+  const SCEVUnknown *DstBase =
+      dyn_cast<SCEVUnknown>(SE->getPointerBase(DstSCEV));
+
+  if (!SrcBase || !DstBase || SrcBase != DstBase)
+    return false;
+
+  SrcSCEV = SE->getMinusSCEV(SrcSCEV, SrcBase);
+  DstSCEV = SE->getMinusSCEV(DstSCEV, DstBase);
+
   const SCEVAddRecExpr *SrcAR = dyn_cast<SCEVAddRecExpr>(SrcSCEV);
   const SCEVAddRecExpr *DstAR = dyn_cast<SCEVAddRecExpr>(DstSCEV);
   if (!SrcAR || !DstAR || !SrcAR->isAffine() || !DstAR->isAffine())
@@ -3200,20 +3211,14 @@ bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
 
   // Third step: compute the access functions for each subscript.
   SmallVector<const SCEV *, 4> SrcSubscripts, DstSubscripts;
-  const SCEV *RemainderS = SrcAR->computeAccessFunctions(*SE, SrcSubscripts, Sizes);
-  const SCEV *RemainderD = DstAR->computeAccessFunctions(*SE, DstSubscripts, Sizes);
+  SrcAR->computeAccessFunctions(*SE, SrcSubscripts, Sizes);
+  DstAR->computeAccessFunctions(*SE, DstSubscripts, Sizes);
 
   // Fail when there is only a subscript: that's a linearized access function.
   if (SrcSubscripts.size() < 2 || DstSubscripts.size() < 2 ||
       SrcSubscripts.size() != DstSubscripts.size())
     return false;
 
-  // When the difference in remainders is different than a constant it might be
-  // that the base address of the arrays is not the same.
-  const SCEV *DiffRemainders = SE->getMinusSCEV(RemainderS, RemainderD);
-  if (!isa<SCEVConstant>(DiffRemainders))
-    return false;
-
   int size = SrcSubscripts.size();
 
   DEBUG({