From f45037b51680d727daa554b8be510a896fa1b9c5 Mon Sep 17 00:00:00 2001
From: Jeremy Furtek <jfurtek@nvidia.com>
Date: Sun, 22 Jun 2025 16:35:37 -0500
Subject: [PATCH] [LLVM] Fix behavior of lookupLLVMIntrinsicByName() with
 StringRefs that are not null-terminated

This PR modifies the implement of lookupLLVMIntrinsicByName(), which may access
uninitialized memory when the StringRef Name argument is not null-terminated.

valgrind reports the following error:

==43697== Conditional jump or move depends on uninitialised value(s)
==43697==    at 0x11B06D28: strlen (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==43697==    by 0x5901C6: std::char_traits<char>::length(char const*) (char_traits.h:399)
==43697==    by 0xAD22C3: llvm::StringRef::StringRef(char const*) (StringRef.h:94)
==43697==    by 0x944BD4A: auto lookupLLVMIntrinsicByName(llvm::ArrayRef<unsigned int>, llvm::StringRef, llvm::StringRef)::{lambda(auto:1, auto:2)#1}::operator()<unsigned int, char const*>(unsigned int, char const*) const (Intrinsics.cpp:768)

Prior to this MR, in the binary search loop, std::equal_range() is called with
the StringRef data pointer. The lambda comparison function assigns an instance
of a StringRef with the const char * value of Name.data() (either LHSStr or
RHSStr). This statement creates an instance of StringRef from the pointer before
invoking the assigment operator. Constructing a StringRef instance from a
pointer calls strlen(), which is incorrect for strings that are not null
terminated.

The MR uses the StringRef as the std::equal_range() value instead of using the
data pointer.
---
 llvm/lib/IR/Intrinsics.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/IR/Intrinsics.cpp b/llvm/lib/IR/Intrinsics.cpp
index e631419d5e1c2..2b3269ecd5b17 100644
--- a/llvm/lib/IR/Intrinsics.cpp
+++ b/llvm/lib/IR/Intrinsics.cpp
@@ -676,7 +676,7 @@ static int lookupLLVMIntrinsicByName(ArrayRef<unsigned> NameOffsetTable,
                      CmpEnd - CmpStart) < 0;
     };
     LastLow = Low;
-    std::tie(Low, High) = std::equal_range(Low, High, Name.data(), Cmp);
+    std::tie(Low, High) = std::equal_range(Low, High, Name, Cmp);
   }
   if (High - Low > 0)
     LastLow = Low;