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Make LSR ignore GEP's that have loop variant base values, as we currently
cannot codegen them

llvm-svn: 22576

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 0967fb7200b..f3834158c1c 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -251,6 +251,9 @@ void LoopStrengthReduce::AnalyzeGetElementPtrUsers(GetElementPtrInst *GEP,
                                                                 UIntPtrTy));
     } else {
       SCEVHandle Idx = SE->getSCEV(GEP->getOperand(i));
+
+      // If this operand is reducible, and it's not the one we are looking at
+      // currently, do not process the GEP at this time.
       if (CanReduceSCEV(Idx, L))
         return;
       Base = SCEVAddExpr::get(Base, GetAdjustedIndex(Idx,
@@ -287,6 +290,13 @@ void LoopStrengthReduce::AnalyzeGetElementPtrUsers(GetElementPtrInst *GEP,
 
   assert(CanReduceSCEV(GEPIndexExpr, L) && "Non reducible idx??");
 
+  // FIXME: If the base is not loop invariant, we currently cannot emit this.
+  if (!Base->isLoopInvariant(L)) {
+    DEBUG(std::cerr << "IGNORING GEP due to non-invaiant base: "
+                    << *Base << "\n");
+    return;
+  }
+  
   Base = SCEVAddExpr::get(Base, cast<SCEVAddRecExpr>(GEPIndexExpr)->getStart());
   SCEVHandle Stride = cast<SCEVAddRecExpr>(GEPIndexExpr)->getOperand(1);