patches: mainline: Add patch to avoid timeout with Hexagon

See the commit message of the patch itself for further details on why
this is needed.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

patches/mainline/20240819_nathan_hexagon_disable_constant_extender_optimization_for_llvm_prior_to_19_1_0.patch

@@ -0,0 +1,61 @@
+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 <nathan@kernel.org>
+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 <bcain@quicinc.com>
+Link: https://lore.kernel.org/r/20240819-hexagon-disable-constant-expander-pass-v1-1-36a734e9527d@kernel.org
+Signed-off-by: Nathan Chancellor <nathan@kernel.org>
+---
+ 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 <nathan@kernel.org>
+

patches/mainline/series

@@ -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