X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FScalarEvolutionExpander.cpp;h=e7fe672ad317c62db0d6424d565ef617698a3a50;hb=864f66085cd9543070ef01b9f7371c110ecd7898;hp=0f2a634a20684ae05839c0a6e75d1a8a50bb005b;hpb=705b48d960dff1a96ac40d0cf932eb465b9a550a;p=oota-llvm.git

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index 0f2a634a206..e7fe672ad31 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -31,11 +31,18 @@ using namespace llvm;
 Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
                                        Instruction::CastOps Op,
                                        BasicBlock::iterator IP) {
-  // All new or reused instructions must strictly dominate their uses.
-  // It would be nice to assert this here, but we don't always know where
-  // the next instructions will be added as the the caller can move the
-  // Builder's InsertPt before creating them and we might be called with
-  // an invalid InsertPt.
+  // This function must be called with the builder having a valid insertion
+  // point. It doesn't need to be the actual IP where the uses of the returned
+  // cast will be added, but it must dominate such IP.
+  // We use this precondition to produce a cast that will dominate all its
+  // uses. In particular, this is crucial for the case where the builder's
+  // insertion point *is* the point where we were asked to put the cast.
+  // Since we don't know the the builder's insertion point is actually
+  // where the uses will be added (only that it dominates it), we are
+  // not allowed to move it.
+  BasicBlock::iterator BIP = Builder.GetInsertPoint();
+
+  Instruction *Ret = NULL;
 
   // Check to see if there is already a cast!
   for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
@@ -44,27 +51,35 @@ Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
     if (U->getType() == Ty)
       if (CastInst *CI = dyn_cast<CastInst>(U))
         if (CI->getOpcode() == Op) {
-          // If the cast isn't where we want it, fix it.
-          if (BasicBlock::iterator(CI) != IP) {
+          // If the cast isn't where we want it, create a new cast at IP.
+          // Likewise, do not reuse a cast at BIP because it must dominate
+          // instructions that might be inserted before BIP.
+          if (BasicBlock::iterator(CI) != IP || BIP == IP) {
             // Create a new cast, and leave the old cast in place in case
             // it is being used as an insert point. Clear its operand
             // so that it doesn't hold anything live.
-            Instruction *NewCI = CastInst::Create(Op, V, Ty, "", IP);
-            NewCI->takeName(CI);
-            CI->replaceAllUsesWith(NewCI);
+            Ret = CastInst::Create(Op, V, Ty, "", IP);
+            Ret->takeName(CI);
+            CI->replaceAllUsesWith(Ret);
             CI->setOperand(0, UndefValue::get(V->getType()));
-            rememberInstruction(NewCI);
-            return NewCI;
+            break;
           }
-          rememberInstruction(CI);
-          return CI;
+          Ret = CI;
+          break;
         }
   }
 
   // Create a new cast.
-  Instruction *I = CastInst::Create(Op, V, Ty, V->getName(), IP);
-  rememberInstruction(I);
-  return I;
+  if (!Ret)
+    Ret = CastInst::Create(Op, V, Ty, V->getName(), IP);
+
+  // We assert at the end of the function since IP might point to an
+  // instruction with different dominance properties than a cast
+  // (an invoke for example) and not dominate BIP (but the cast does).
+  assert(SE.DT->dominates(Ret, BIP));
+
+  rememberInstruction(Ret);
+  return Ret;
 }
 
 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
@@ -504,8 +519,7 @@ Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
        Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace()));
 
     assert(!isa<Instruction>(V) ||
-           SE.DT->properlyDominates(cast<Instruction>(V),
-                                    Builder.GetInsertPoint()));
+           SE.DT->dominates(cast<Instruction>(V), Builder.GetInsertPoint()));
 
     // Expand the operands for a plain byte offset.
     Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
@@ -897,7 +911,7 @@ Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
   case Instruction::Add:
   case Instruction::Sub: {
     Instruction *OInst = dyn_cast<Instruction>(IncV->getOperand(1));
-    if (!OInst || SE.DT->properlyDominates(OInst, InsertPos))
+    if (!OInst || SE.DT->dominates(OInst, InsertPos))
       return dyn_cast<Instruction>(IncV->getOperand(0));
     return NULL;
   }
@@ -909,7 +923,7 @@ Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
       if (isa<Constant>(*I))
         continue;
       if (Instruction *OInst = dyn_cast<Instruction>(*I)) {
-        if (!SE.DT->properlyDominates(OInst, InsertPos))
+        if (!SE.DT->dominates(OInst, InsertPos))
           return NULL;
       }
       if (allowScale) {
@@ -936,12 +950,13 @@ Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
 /// it available to other uses in this loop. Recursively hoist any operands,
 /// until we reach a value that dominates InsertPos.
 bool SCEVExpander::hoistIVInc(Instruction *IncV, Instruction *InsertPos) {
-  if (SE.DT->properlyDominates(IncV, InsertPos))
+  if (SE.DT->dominates(IncV, InsertPos))
       return true;
 
   // InsertPos must itself dominate IncV so that IncV's new position satisfies
   // its existing users.
-  if (!SE.DT->dominates(InsertPos->getParent(), IncV->getParent()))
+  if (isa<PHINode>(InsertPos)
+      || !SE.DT->dominates(InsertPos->getParent(), IncV->getParent()))
     return false;
 
   // Check that the chain of IV operands leading back to Phi can be hoisted.
@@ -953,7 +968,7 @@ bool SCEVExpander::hoistIVInc(Instruction *IncV, Instruction *InsertPos) {
     // IncV is safe to hoist.
     IVIncs.push_back(IncV);
     IncV = Oper;
-    if (SE.DT->properlyDominates(IncV, InsertPos))
+    if (SE.DT->dominates(IncV, InsertPos))
       break;
   }
   for (SmallVectorImpl<Instruction*>::reverse_iterator I = IVIncs.rbegin(),