3 files changed, 10 insertions, 25 deletions

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index 52dd06affe..bdf7dee662 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -623,7 +623,8 @@ void LICM::hoist(Instruction &I) {
 ///
 bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) {
   // If it is not a trapping instruction, it is always safe to hoist.
-  if (!Inst.isTrapping()) return true;
+  if (Inst.isSafeToSpeculativelyExecute())
+    return true;
 
   // Otherwise we have to check to make sure that the instruction dominates all
   // of the exit blocks.  If it doesn't, then there is a path out of the loop
@@ -635,12 +636,6 @@ bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) {
   if (Inst.getParent() == CurLoop->getHeader())
     return true;
 
-  // It's always safe to load from a global or alloca.
-  if (isa<LoadInst>(Inst))
-    if (isa<AllocationInst>(Inst.getOperand(0)) ||
-        isa<GlobalVariable>(Inst.getOperand(0)))
-      return true;
-
   // Get the exit blocks for the current loop.
   SmallVector<BasicBlock*, 8> ExitBlocks;
   CurLoop->getExitBlocks(ExitBlocks);
diff --git a/lib/Transforms/Scalar/TailDuplication.cpp b/lib/Transforms/Scalar/TailDuplication.cpp
index 684b096345..6d05fdf18c 100644
--- a/lib/Transforms/Scalar/TailDuplication.cpp
+++ b/lib/Transforms/Scalar/TailDuplication.cpp
@@ -258,7 +258,8 @@ void TailDup::eliminateUnconditionalBranch(BranchInst *Branch) {
     while (!isa<TerminatorInst>(BBI)) {
       Instruction *I = BBI++;
 
-      bool CanHoist = !I->isTrapping() && !I->mayHaveSideEffects();
+      bool CanHoist = I->isSafeToSpeculativelyExecute() &&
+                      !I->mayReadFromMemory();
       if (CanHoist) {
         for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
           if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(op)))
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 55e1bf225c..3b6b77f5fb 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -384,26 +384,15 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
       // Okay, it looks like the instruction IS in the "condition".  Check to
       // see if its a cheap instruction to unconditionally compute, and if it
       // only uses stuff defined outside of the condition.  If so, hoist it out.
+      if (!I->isSafeToSpeculativelyExecute())
+        return false;
+
       switch (I->getOpcode()) {
       default: return false;  // Cannot hoist this out safely.
       case Instruction::Load: {
-        // We can hoist loads that are non-volatile and obviously cannot trap.
-        if (cast<LoadInst>(I)->isVolatile())
-          return false;
-        // FIXME: A computation of a constant can trap!
-        if (!isa<AllocaInst>(I->getOperand(0)) &&
-            !isa<Constant>(I->getOperand(0)))
-          return false;
-        // External weak globals may have address 0, so we can't load them.
-        Value *V2 = I->getOperand(0)->getUnderlyingObject();
-        if (V2) {
-          GlobalVariable* GV = dyn_cast<GlobalVariable>(V2);
-          if (GV && GV->hasExternalWeakLinkage())
-            return false;
-        }
-        // Finally, we have to check to make sure there are no instructions
-        // before the load in its basic block, as we are going to hoist the loop
-        // out to its predecessor.
+        // We have to check to make sure there are no instructions before the
+        // load in its basic block, as we are going to hoist the loop out to
+        // its predecessor.
         BasicBlock::iterator IP = PBB->begin();
         while (isa<DbgInfoIntrinsic>(IP))
           IP++;