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hexagon: Disable constant extender optimization for LLVM prior to 19.1.0

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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: 68df06a0b2 [2]
Link: 2ab8d93061 [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>
This commit is contained in:
Nathan Chancellor 2024-11-21 11:22:18 -07:00 committed by Linus Torvalds
parent 5529876063
commit aef25be35d
1 changed files with 6 additions and 0 deletions
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6
arch/hexagon/Makefile
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@ -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