Update LLVM to r108243.

1 files changed, 15 insertions, 5 deletions

diff --git a/lib/VMCore/Instruction.cpp b/lib/VMCore/Instruction.cpp
index a37fe07..9792ada 100644
--- a/lib/VMCore/Instruction.cpp
+++ b/lib/VMCore/Instruction.cpp
@@ -286,9 +286,10 @@ bool Instruction::isUsedOutsideOfBlock(const BasicBlock *BB) const {
   for (const_use_iterator UI = use_begin(), E = use_end(); UI != E; ++UI) {
     // PHI nodes uses values in the corresponding predecessor block.  For other
     // instructions, just check to see whether the parent of the use matches up.
-    const PHINode *PN = dyn_cast<PHINode>(*UI);
+    const User *U = *UI;
+    const PHINode *PN = dyn_cast<PHINode>(U);
     if (PN == 0) {
-      if (cast<Instruction>(*UI)->getParent() != BB)
+      if (cast<Instruction>(U)->getParent() != BB)
         return true;
       continue;
     }
@@ -401,12 +402,20 @@ bool Instruction::isSafeToSpeculativelyExecute() const {
       return false;
     // Note that it is not safe to speculate into a malloc'd region because
     // malloc may return null.
-    if (isa<AllocaInst>(getOperand(0)))
+    // It's also not safe to follow a bitcast, for example:
+    //   bitcast i8* (alloca i8) to i32*
+    // would result in a 4-byte load from a 1-byte alloca.
+    Value *Op0 = getOperand(0);
+    if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0)) {
+      // TODO: it's safe to do this for any GEP with constant indices that
+      // compute inside the allocated type, but not for any inbounds gep.
+      if (GEP->hasAllZeroIndices())
+        Op0 = GEP->getPointerOperand();
+    }
+    if (isa<AllocaInst>(Op0))
       return true;
     if (GlobalVariable *GV = dyn_cast<GlobalVariable>(getOperand(0)))
       return !GV->hasExternalWeakLinkage();
-    // FIXME: Handle cases involving GEPs.  We have to be careful because
-    // a load of a out-of-bounds GEP has undefined behavior.
     return false;
   }
   case Call:
@@ -421,6 +430,7 @@ bool Instruction::isSafeToSpeculativelyExecute() const {
   case Store:
   case Ret:
   case Br:
+  case IndirectBr:
   case Switch:
   case Unwind:
   case Unreachable: