-----Original Message----- From: Brian Cain bcain@quicinc.com Sent: Tuesday, December 17, 2024 8:11 PM To: Nathan Chancellor nathan@kernel.org; Andrew Morton <akpm@linux- foundation.org>; Linus Torvalds torvalds@linux-foundation.org Cc: linux-hexagon@vger.kernel.org; patches@lists.linux.dev; llvm@lists.linux.dev; stable@vger.kernel.org; linux-kernel@vger.kernel.org Subject: RE: [PATCH v2] hexagon: Disable constant extender optimization for LLVM prior to 19.1.0
-----Original Message----- From: Nathan Chancellor nathan@kernel.org Sent: Tuesday, December 17, 2024 11:44 AM To: Brian Cain bcain@quicinc.com; Andrew Morton <akpm@linux- foundation.org>; Linus Torvalds torvalds@linux-foundation.org Cc: linux-hexagon@vger.kernel.org; patches@lists.linux.dev; llvm@lists.linux.dev; stable@vger.kernel.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] hexagon: Disable constant extender optimization for LLVM prior to 19.1.0
Hi Linus,
Could you apply this change [1] directly? Brian has reviewed it and I have sent this patch twice plus another ping for application [2]. I would like to stop applying this in our CI and some other people have hit it as well.
Nathan,
I'm sorry. You should not have to send these changes to Linus. I should have carried it in my tree and proposed it to Linus.
I'll do that, if you don't mind.
I see it's landed. Sorry, all. I'll resolve to do a better job here.
expander-pass-v2-1-1a92e9afb0f4@kernel.org/ [2]: https://lore.kernel.org/all/20241001185848.GA562711@thelio-
3990X/
Cheers, Nathan
On Thu, Nov 21, 2024 at 11:22:18AM -0700, Nathan Chancellor wrote:
The Hexagon-specific constant extender optimization in LLVM may crash
on
Linux kernel code [1], such as fs/bcache/btree_io.c after commit 32ed4a620c54 ("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
<eof> parser at end of fileCode generationRunning pass 'Function Pass Manager' on module'fs/bcachefs/btree_io.c'.
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]
project/commit/2ab8d93061581edad3501561722ebd5632d73892 [3]
Reviewed-by: Brian Cain bcain@quicinc.com Signed-off-by: Nathan Chancellor nathan@kernel.org
Andrew, can you please take this for 6.13? Our CI continues to hit this.
Changes in v2:
- Rebase on 6.12 to make sure it is still applicable
- Name exact bcachefs commit that introduces crash now that it is merged
- Add 'Cc: stable' as this is now visible in a stable release
- Carry forward Brian's reviewed-by
- Link to v1: https://lore.kernel.org/r/20240819-hexagon-disable-
constant-
expander-pass-v1-1-36a734e9527d@kernel.org
arch/hexagon/Makefile | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/hexagon/Makefile b/arch/hexagon/Makefile index
92d005958dfb232d48a4ca843b46262a84a08eb4..ff172cbe5881a074f9d94
30c37071992a4c8beac 100644
--- a/arch/hexagon/Makefile +++ b/arch/hexagon/Makefile @@ -32,3 +32,9 @@ KBUILD_LDFLAGS += $(ldflags-y) TIR_NAME := r19 KBUILD_CFLAGS += -ffixed-$(TIR_NAME) -
DTHREADINFO_REG=$(TIR_NAME) -D__linux__
KBUILD_AFLAGS += -DTHREADINFO_REG=$(TIR_NAME)
+# Disable HexagonConstExtenders pass for LLVM versions prior to 19.1.0 +# https://github.com/llvm/llvm-project/issues/99714 +ifneq ($(call clang-min-version, 190100),y) +KBUILD_CFLAGS += -mllvm -hexagon-cext=false +endif
base-commit: adc218676eef25575469234709c2d87185ca223a change-id: 20240802-hexagon-disable-constant-expander-pass-
8b6b61db6afc
Best regards,
Nathan Chancellor nathan@kernel.org