Don't skip debug instructions when looking for the insertion point of

the cast. If we do, we can end up with

   inst1
   ---------------  < Insertion point
   dbg inst
   new inst

instead of the desired

   inst1
   new inst
   ---------------  < Insertion point
   dbg inst

Another option would be for InsertNoopCastOfTo (or its callers) to move the
insertion point and we would end up with

   inst1
   dbg inst
   new inst
   ---------------  < Insertion point

but that complicates the callers. This fixes PR12018 (and firefox's build).

llvm-svn: 150884

1 files changed, 8 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
index f5598897995..58181fb09f6 100644
--- a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -31,6 +31,12 @@ using namespace llvm;
 Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
                                        Instruction::CastOps Op,
                                        BasicBlock::iterator IP) {
+  // All new or reused instructions must strictly dominate the Builder's
+  // InsertPt to ensure that the expression's expansion dominates its uses.
+  // Assert that the requested insertion point works at least for new
+  // instructions.
+  assert(SE.DT->dominates(IP, Builder.GetInsertPoint()));
+
   // Check to see if there is already a cast!
   for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
        UI != E; ++UI) {
@@ -38,9 +44,7 @@ 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. All new or reused
-          // instructions must strictly dominate the Builder's InsertPt to
-          // ensure that the expression's expansion dominates its uses.
+          // If the cast isn't where we want it, fix it.
           if (BasicBlock::iterator(CI) != IP
               || IP == Builder.GetInsertPoint()) {
             // Create a new cast, and leave the old cast in place in case
@@ -124,8 +128,7 @@ Value *SCEVExpander::InsertNoopCastOfTo(Value *V, Type *Ty) {
   BasicBlock::iterator IP = I; ++IP;
   if (InvokeInst *II = dyn_cast<InvokeInst>(I))
     IP = II->getNormalDest()->begin();
-  while (isa<PHINode>(IP) || isa<DbgInfoIntrinsic>(IP) ||
-         isa<LandingPadInst>(IP))
+  while (isa<PHINode>(IP) || isa<LandingPadInst>(IP))
     ++IP;
   return ReuseOrCreateCast(I, Ty, Op, IP);
 }