hexagon: Disable constant extender optimization for LLVM prior to 19.1.0

nathanchance · Sasha Levin · commit 2ba18a88179d · 2024-12-23T10:55:19.000-05:00
commit aef25be upstream. The Hexagon-specific constant extender optimization in LLVM may crash on Linux kernel code [1], such as fs/bcache/btree_io.c after commit 32ed4a6 ("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: llvm/llvm-project#99714 [1] Link: llvm/llvm-project@68df06a [2] Link: llvm/llvm-project@2ab8d93 [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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git 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
