From: Nick Desaulniers <ndesaulniers@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
Nathan Chancellor <nathan@kernel.org>
Cc: Khem Raj <raj.khem@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Michal Marek <michal.lkml@markovi.net>,
Jonathan Corbet <corbet@lwn.net>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-riscv@lists.infradead.org
Subject: [PATCH] scripts/Makefile.clang: default to LLVM_IAS=1
Date: Mon, 2 Aug 2021 16:43:03 -0700 [thread overview]
Message-ID: <20210802234304.3519577-1-ndesaulniers@google.com> (raw)
LLVM_IAS=1 controls enabling clang's integrated assembler via
-integrated-as. This was an explicit opt in until we could enable
assembler support in Clang for more architecures. Now we have support
and CI coverage of LLVM_IAS=1 for all architecures except a few more
bugs affecting s390 and powerpc.
This commit flips the default from opt in via LLVM_IAS=1 to opt out via
LLVM_IAS=0. CI systems or developers that were previously doing builds
with CC=clang or LLVM=1 without explicitly setting LLVM_IAS must now
explicitly opt out via LLVM_IAS=0, otherwise they will be implicitly
opted-in.
This finally shortens the command line invocation when cross compiling
with LLVM to simply:
$ make ARCH=arm64 LLVM=1
Link: https://github.com/ClangBuiltLinux/linux/issues/1434
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Note: base is:
https://lore.kernel.org/lkml/20210802183910.1802120-1-ndesaulniers@google.com/
Documentation/kbuild/llvm.rst | 14 ++++++++------
Makefile | 2 +-
arch/riscv/Makefile | 2 +-
scripts/Makefile.clang | 6 +++---
4 files changed, 13 insertions(+), 11 deletions(-)
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index f8a360958f4c..16712fab4d3a 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -60,17 +60,14 @@ They can be enabled individually. The full list of the parameters: ::
OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \
HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld
-Currently, the integrated assembler is disabled by default. You can pass
-``LLVM_IAS=1`` to enable it.
+Currently, the integrated assembler is enabled by default. You can pass
+``LLVM_IAS=0`` to disable it.
Omitting CROSS_COMPILE
----------------------
As explained above, ``CROSS_COMPILE`` is used to set ``--target=<triple>``.
-Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive
-``--prefix=<path>`` to search for the GNU assembler and linker.
-
If ``CROSS_COMPILE`` is not specified, the ``--target=<triple>`` is inferred
from ``ARCH``.
@@ -78,7 +75,12 @@ That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary.
For example, to cross-compile the arm64 kernel::
- make ARCH=arm64 LLVM=1 LLVM_IAS=1
+ make ARCH=arm64 LLVM=1
+
+If ``LLVM_IAS=0`` is specified, ``CROSS_COMPILE`` is also used to derive
+``--prefix=<path>`` to search for the GNU assembler and linker. ::
+
+ make ARCH=arm64 LLVM=1 LLVM_IAS=0 CROSS_COMPILE=aarch64-linux-gnu-
Supported Architectures
-----------------------
diff --git a/Makefile b/Makefile
index 444558e62cbc..b24b48c9ebb7 100644
--- a/Makefile
+++ b/Makefile
@@ -845,7 +845,7 @@ else
DEBUG_CFLAGS += -g
endif
-ifneq ($(LLVM_IAS),1)
+ifeq ($(LLVM_IAS),0)
KBUILD_AFLAGS += -Wa,-gdwarf-2
endif
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index bc74afdbf31e..807f7c94bc6f 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -41,7 +41,7 @@ endif
ifeq ($(CONFIG_LD_IS_LLD),y)
KBUILD_CFLAGS += -mno-relax
KBUILD_AFLAGS += -mno-relax
-ifneq ($(LLVM_IAS),1)
+ifeq ($(LLVM_IAS),0)
KBUILD_CFLAGS += -Wa,-mno-relax
KBUILD_AFLAGS += -Wa,-mno-relax
endif
diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
index 1f4e3eb70f88..3ae63bd35582 100644
--- a/scripts/Makefile.clang
+++ b/scripts/Makefile.clang
@@ -22,12 +22,12 @@ else
CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
endif # CROSS_COMPILE
-ifeq ($(LLVM_IAS),1)
-CLANG_FLAGS += -integrated-as
-else
+ifeq ($(LLVM_IAS),0)
CLANG_FLAGS += -no-integrated-as
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
+else
+CLANG_FLAGS += -integrated-as
endif
CLANG_FLAGS += -Werror=unknown-warning-option
KBUILD_CFLAGS += $(CLANG_FLAGS)
base-commit: d7a86429dbc691bf540688fcc8542cc20246a85b
prerequisite-patch-id: 0d3072ecb5fd06ff6fd6ea81fe601f6c54c23910
prerequisite-patch-id: 2654829756eb8a094a0ffad1679caa75a4d86619
prerequisite-patch-id: a51e7885ca2376d008bbf146a5589da247806f7b
--
2.32.0.554.ge1b32706d8-goog
next reply other threads:[~2021-08-02 23:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-02 23:43 Nick Desaulniers [this message]
2021-08-03 1:32 ` [PATCH] scripts/Makefile.clang: default to LLVM_IAS=1 Matthew Wilcox
2021-08-05 13:59 ` Masahiro Yamada
2021-08-03 1:42 ` Khem Raj
2021-08-05 15:15 ` Masahiro Yamada
2021-08-05 15:18 ` Khem Raj
2021-08-05 18:40 ` Nick Desaulniers
2021-08-05 23:48 ` Masahiro Yamada
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210802234304.3519577-1-ndesaulniers@google.com \
--to=ndesaulniers@google.com \
--cc=aou@eecs.berkeley.edu \
--cc=clang-built-linux@googlegroups.com \
--cc=corbet@lwn.net \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=masahiroy@kernel.org \
--cc=michal.lkml@markovi.net \
--cc=nathan@kernel.org \
--cc=palmer@dabbelt.com \
--cc=paul.walmsley@sifive.com \
--cc=raj.khem@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).