allow -1 strides to reuse "1" strides.

[oota-llvm.git] / lib / Transforms / Scalar / LoopStrengthReduce.cpp

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 4ace17f7a4a0fa86a735732362b27b0b44f31184..db8ab485e394c428ae1b60e83ab27864e3f17893 100644 (file)
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -235,6 +235,16 @@ DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) {
 /// GetExpressionSCEV - Compute and return the SCEV for the specified
 /// instruction.
 SCEVHandle LoopStrengthReduce::GetExpressionSCEV(Instruction *Exp, Loop *L) {
+  // Pointer to pointer bitcast instructions return the same value as their
+  // operand.
+  if (BitCastInst *BCI = dyn_cast<BitCastInst>(Exp)) {
+    if (SE->hasSCEV(BCI) || !isa<Instruction>(BCI->getOperand(0)))
+      return SE->getSCEV(BCI);
+    SCEVHandle R = GetExpressionSCEV(cast<Instruction>(BCI->getOperand(0)), L);
+    SE->setSCEV(BCI, R);
+    return R;
+  }
+
   // Scalar Evolutions doesn't know how to compute SCEV's for GEP instructions.
   // If this is a GEP that SE doesn't know about, compute it now and insert it.
   // If this is not a GEP, or if we have already done this computation, just let
@@ -889,8 +899,15 @@ bool LoopStrengthReduce::ValidStride(int64_t Scale,
       Imm = SC->getValue()->getSExtValue();
     else
       Imm = 0;
-    if (!TLI->isLegalAddressScaleAndImm(Scale, Imm, 
-                                  UsersToProcess[i].Inst->getType()))
+    
+    // If this is a load or other access, pass the type of the access in.
+    const Type *AccessTy = Type::VoidTy;
+    if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].Inst))
+      AccessTy = SI->getOperand(0)->getType();
+    else if (LoadInst *LI = dyn_cast<LoadInst>(UsersToProcess[i].Inst))
+      AccessTy = LI->getType();
+    
+    if (!TLI->isLegalAddressScaleAndImm(Scale, Imm, AccessTy))
       return false;
   }
   return true;
@@ -912,7 +929,8 @@ unsigned LoopStrengthReduce::CheckForIVReuse(const SCEVHandle &Stride,
     for (std::map<SCEVHandle, IVsOfOneStride>::iterator SI= IVsByStride.begin(),
            SE = IVsByStride.end(); SI != SE; ++SI) {
       int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
-      if (unsigned(abs(SInt)) < SSInt || (SInt % SSInt) != 0)
+      if (SInt != -SSInt &&
+          (unsigned(abs(SInt)) < SSInt || (SInt % SSInt) != 0))
         continue;
       int64_t Scale = SInt / SSInt;
       // Check that this stride is valid for all the types used for loads and
@@ -1019,10 +1037,12 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
     IncV   = ReuseIV.IncV;
   }
 
+  const Type *ReplacedTy = CommonExprs->getType();
+  
   // Now that we know what we need to do, insert the PHI node itself.
   //
-  DOUT << "INSERTING IV of STRIDE " << *Stride << " and BASE "
-       << *CommonExprs << " :\n";
+  DOUT << "INSERTING IV of TYPE " << *ReplacedTy << " of STRIDE "
+       << *Stride << " and BASE " << *CommonExprs << " :\n";
 
   SCEVExpander Rewriter(*SE, *LI);
   SCEVExpander PreheaderRewriter(*SE, *LI);
@@ -1033,7 +1053,6 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
   
   BasicBlock *LatchBlock = L->getLoopLatch();
 
-  const Type *ReplacedTy = CommonExprs->getType();
 
   // Emit the initial base value into the loop preheader.
   Value *CommonBaseV