[all-commits] [llvm/llvm-project] 183f1a: [LLVM] Fix an ASAN error in `lookupLLVMIntrinsicBy...

[Rahul Joshi via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 183f1ac412c1a0c69c7dc6aef85c28c0749609cb
      https://github.com/llvm/llvm-project/commit/183f1ac412c1a0c69c7dc6aef85c28c0749609cb
  Author: Rahul Joshi <rjoshi at nvidia.com>
  Date:   2025-07-15 (Tue, 15 Jul 2025)

  Changed paths:
    M llvm/include/llvm/ADT/StringTable.h
    M llvm/lib/IR/Intrinsics.cpp
    M llvm/unittests/IR/IntrinsicsTest.cpp

  Log Message:
  -----------
  [LLVM] Fix an ASAN error in `lookupLLVMIntrinsicByName` (#147444)

Fix unnecessary conversion of C-String to StringRef in the `Cmp` lambda
inside `lookupLLVMIntrinsicByName`. This both fixes an ASAN error in the
code that happens when the `Name` StringRef passed in is not a Null
terminated StringRef, and additionally can potentially speed up the code
as well by eliminating the unnecessary computation of string length
every time a C String is converted to StringRef in this code (It seems
practically this computation is eliminated in optimized builds, but this
will avoid it in O0 builds as well).

Added a unit test that demonstrates this issue by building LLVM with
these options:

```
CMAKE_BUILD_TYPE=Debug
LLVM_USE_SANITIZER=Address
LLVM_OPTIMIZE_SANITIZED_BUILDS=OFF
```

The error reported is as follows:

```
==462665==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x5030000391a2 at pc 0x56525cc30bbf bp 0x7fff9e4ccc60 sp 0x7fff9e4cc428
READ of size 19 at 0x5030000391a2 thread T0
    #0 0x56525cc30bbe in strlen (upstream-llvm-second/llvm-project/build/unittests/IR/IRTests+0x713bbe) (BuildId: 0651acf1e582a4d2)
    #1 0x7f8ff22ad334 in std::char_traits<char>::length(char const*) /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/char_traits.h:399:9
    #2 0x7f8ff22a34a0 in llvm::StringRef::StringRef(char const*) /home/rjoshi/upstream-llvm-second/llvm-project/llvm/include/llvm/ADT/StringRef.h:96:33
    #3 0x7f8ff28ca184 in _ZZL25lookupLLVMIntrinsicByNameN4llvm8ArrayRefIjEENS_9StringRefES2_ENK3$_0clIjPKcEEDaT_T0_ upstream-llvm-second/llvm-project/llvm/lib/IR/Intrinsics.cpp:673:18
```



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