Assertion failure in llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp after commit f91cc09a5a90 in -next

[nathanchance]

After commit f91cc09a5a90 ("bcachefs: Btree path tracepoints") in linux-next, there is a crash when assertions are enabled (or a hang when they are not):

$ make -skj"$(nproc)" ARCH=hexagon LLVM=1 mrproper allmodconfig fs/bcachefs/btree_io.o
clang: llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp:745: bool (anonymous namespace)::HexagonConstExtenders::ExtRoot::operator<(const HCE::ExtRoot &) const: Assertion `ThisB->getParent() == OtherB->getParent()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /home/nathan/cbl/toolchains/llvm-latest/bin/clang --target=hexagon-linux-musl -fintegrated-as .../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'
...

I reported this upstream at llvm/llvm-project#99714.

I plan to send this diff soon to avoid this problematic pass for now, eventually changing it to be gated by a broken version check.

diff --git a/arch/hexagon/Makefile b/arch/hexagon/Makefile
index 92d005958dfb..49679120e975 100644
--- a/arch/hexagon/Makefile
+++ b/arch/hexagon/Makefile
@@ -32,3 +32,6 @@ KBUILD_LDFLAGS += $(ldflags-y)
 TIR_NAME := r19
 KBUILD_CFLAGS += -ffixed-$(TIR_NAME) -DTHREADINFO_REG=$(TIR_NAME) -D__linux__
 KBUILD_AFLAGS += -DTHREADINFO_REG=$(TIR_NAME)
+
+# https://github.com/llvm/llvm-project/issues/99714
+KBUILD_CFLAGS += -mllvm -hexagon-cext=false

[nathanchance]

This is now fixed in main: llvm/llvm-project@68df06a

A backport to 19.1 has been requested, so I will send the above change once that is merged.

[nathanchance]

Workaround for older releases submitted as the patch has been back ported to 19.1: https://lore.kernel.org/20240819-hexagon-disable-constant-expander-pass-v1-1-36a734e9527d@kernel.org