diff options
| -rw-r--r-- | lib/Analysis/BasicAliasAnalysis.cpp | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index b19ce2b..c4153b9 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -252,19 +252,21 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) { if (Object && (isa<AllocationInst>(Object) || isa<Argument>(Object))) { // Okay, the pointer is to a stack allocated (or effectively so, for - // for noalias parameters) object. If we can prove that - // the pointer never "escapes", then we know the call cannot clobber it, - // because it simply can't get its address. + // for noalias parameters) object. If the address of this object doesn't + // escape from this function body to a callee, then we know that no + // callees can mod/ref it unless they are actually passed it. if (isa<AllocationInst>(Object) || cast<Argument>(Object)->hasByValAttr() || cast<Argument>(Object)->hasNoAliasAttr()) if (!AddressMightEscape(Object)) { + bool passedAsArg = false; for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end(); CI != CE; ++CI) if (getUnderlyingObject(CI->get()) == P) - return AliasAnalysis::getModRefInfo(CS, P, Size); - - return NoModRef; + passedAsArg = true; + + if (!passedAsArg) + return NoModRef; } // If this is a tail call and P points to a stack location, we know that |