lisa/android_kernel_xiaomi_sm8350
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

UPSTREAM: Makefile: Only specify '--prefix=' when building with clang + GNU as

Browse Source 
When building with LLVM_IAS=1, there is no point to specifying
'--prefix=' because that flag is only used to find GNU cross tools,
which will not be used indirectly when using the integrated assembler.
All of the tools are invoked directly from PATH or a full path specified
via the command line, which does not depend on the value of '--prefix='.

Sharing commands to reproduce issues becomes a little bit easier without
a '--prefix=' value because that '--prefix=' value is specific to a
user's machine due to it being an absolute path.

Some further notes from Fangrui Song:

  clang can spawn GNU as (if -f?no-integrated-as is specified) and GNU
  objcopy (-f?no-integrated-as and -gsplit-dwarf and -g[123]).
  objcopy is only used for GNU as assembled object files.
  With integrated assembler, the object file streamer creates .o and
  .dwo simultaneously.
  With GNU as, two objcopy commands are needed to extract .debug*.dwo to
  .dwo files && another command to remove .debug*.dwo sections.

A small consequence of this change (to keep things simple) is that
'--prefix=' will always be specified now, even with a native build, when
it was not before. This should not be an issue due to the way that the
Makefile searches for the prefix (based on elfedit's location). This
ends up improving the experience for host builds because PATH is better
respected and matches GCC's behavior more closely. See the below thread
for more details:

https://lore.kernel.org/r/20210205213651.GA16907@Ryzen-5-4500U.localdomain/

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
(cherry picked from commit eec08090bcc113643522d4272dc0b945045aba74)
Bug: 209655537
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Change-Id: I90f232a1551afb9118176a61ac5de38384a171fd
This commit is contained in:
Nathan Chancellor 2021-03-09 13:59:15 -07:00 committed by Michael Bestas
parent 47b2c24d9d
commit 980f272ee9
No known key found for this signature in database
GPG Key ID: CC95044519BE6669
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Makefile
View File

@ -562,11 +562,11 @@ CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed 's/\#//g
ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
ifneq ($(CROSS_COMPILE),)
CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
endif
ifneq ($(LLVM_IAS),1)
CLANG_FLAGS += -no-integrated-as
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
endif
CLANG_FLAGS += -Werror=unknown-warning-option
KBUILD_CFLAGS += $(CLANG_FLAGS)