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Nathan Chancellor
aef25be35d
The Hexagon-specific constant extender optimization in LLVM may crash on
Linux kernel code [1], such as fs/bcache/btree_io.c after
commit 32ed4a620c ("bcachefs: Btree path tracepoints") in 6.12:
clang: llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp:745: bool (anonymous namespace)::HexagonConstExtenders::ExtRoot::operator<(const HCE::ExtRoot &) const: Assertion `ThisB->getParent() == OtherB->getParent()' failed.
Stack dump:
0. Program arguments: clang --target=hexagon-linux-musl ... fs/bcachefs/btree_io.c
1. <eof> parser at end of file
2. Code generation
3. Running pass 'Function Pass Manager' on module 'fs/bcachefs/btree_io.c'.
4. Running pass 'Hexagon constant-extender optimization' on function '@__btree_node_lock_nopath'
Without assertions enabled, there is just a hang during compilation.
This has been resolved in LLVM main (20.0.0) [2] and backported to LLVM
19.1.0 but the kernel supports LLVM 13.0.1 and newer, so disable the
constant expander optimization using the '-mllvm' option when using a
toolchain that is not fixed.
Cc: stable@vger.kernel.org
Link: https://github.com/llvm/llvm-project/issues/99714 [1]
Link: https://github.com/llvm/llvm-project/commit/68df06a0b2998765cb0a41353fcf0919bbf57ddb [2]
Link: https://github.com/llvm/llvm-project/commit/2ab8d93061581edad3501561722ebd5632d73892 [3]
Reviewed-by: Brian Cain <bcain@quicinc.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.