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patches: mainline: Add patch to avoid timeout with Hexagon
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nathanchance authored Oct 2, 2024
2 parents 3ef34e1 + 7817b25 commit 4f94cb6
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From git@z Thu Jan 1 00:00:00 1970
Subject: [PATCH] hexagon: Disable constant extender optimization for LLVM
prior to 19.1.0
From: Nathan Chancellor <[email protected]>
Date: Mon, 19 Aug 2024 11:16:10 -0700
Message-Id: <20240819-hexagon-disable-constant-expander-pass-v1-1-36a734e9527d@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit

The Hexagon-specific constant extender optimization in LLVM may crash on
Linux kernel code [1] (such as with a bcachefs change in -next):

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.

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 <[email protected]>
Link: https://lore.kernel.org/r/20240819-hexagon-disable-constant-expander-pass-v1-1-36a734e9527d@kernel.org
Signed-off-by: Nathan Chancellor <[email protected]>
---
arch/hexagon/Makefile | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/hexagon/Makefile b/arch/hexagon/Makefile
index 92d005958dfb..ff172cbe5881 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: 47ac09b91befbb6a235ab620c32af719f8208399
change-id: 20240802-hexagon-disable-constant-expander-pass-8b6b61db6afc

Best regards,
--
Nathan Chancellor <[email protected]>

1 change: 1 addition & 0 deletions patches/mainline/series
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@@ -1 +1,2 @@
20240819_nathan_hexagon_disable_constant_extender_optimization_for_llvm_prior_to_19_1_0.patch
v2_20240916_dan_carpenter_iio_bmi323_fix_copy_and_paste_bugs_in_suspend_resume.patch

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