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

1 files changed, 7 insertions, 3 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index bfdc17eff7..b5fd0b9af4 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -759,9 +759,13 @@ protected:
                            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();