Factor out Instruction::isSafeToSpeculativelyExecute's code for

[oota-llvm.git] / lib / VMCore / Instruction.cpp

diff --git a/lib/VMCore/Instruction.cpp b/lib/VMCore/Instruction.cpp
index 05bed4c64316fa77e406ec96153c6ccd0c700bd0..fdddba988c3d133c751089637bd130baf0ee5a31 100644 (file)
--- a/lib/VMCore/Instruction.cpp
+++ b/lib/VMCore/Instruction.cpp
@@ -398,25 +398,10 @@ bool Instruction::isSafeToSpeculativelyExecute() const {
     return Op && !Op->isNullValue() && !Op->isAllOnesValue();
   }
   case Load: {
-    if (cast<LoadInst>(this)->isVolatile())
+    const LoadInst *LI = cast<LoadInst>(this);
+    if (LI->isVolatile())
       return false;
-    // Note that it is not safe to speculate into a malloc'd region because
-    // malloc may return null.
-    // 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();
-    return false;
+    return LI->getPointerOperand()->isDereferenceablePointer();
   }
   case Call:
     return false; // The called function could have undefined behavior or