If we don't know how long a string is we can't fold an _chk version to the
normal version.
Fixes rdar://9123638
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127636 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index bfdc17e..b5fd0b9 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -759,9 +759,13 @@
dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp))) {
if (SizeCI->isAllOnesValue())
return true;
- if (isString)
- return SizeCI->getZExtValue() >=
- GetStringLength(CI->getArgOperand(SizeArgOp));
+ if (isString) {
+ uint64_t Len = GetStringLength(CI->getArgOperand(SizeArgOp));
+ // If the length is 0 we don't know how long it is and so we can't
+ // remove the check.
+ if (Len == 0) return false;
+ return SizeCI->getZExtValue() >= Len;
+ }
if (ConstantInt *Arg = dyn_cast<ConstantInt>(
CI->getArgOperand(SizeArgOp)))
return SizeCI->getZExtValue() >= Arg->getZExtValue();