[PATCH 4.4 29/70] x86/kbuild: Use cc-option to enable -falign-{jumps/loops}

Greg Kroah-Hartman
2018-11-26T10:54:39Z

From: Matthias Kaehlcke <mka@chromium.org>

commit 2c4fd1ac3ff167c91272dc43c7bfd2269ef61557 upstream.

clang currently does not support these optimizations, only enable them
when they are available.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michael Davidson <md@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: grundler@chromium.org
Link: http://lkml.kernel.org/r/20170413172609.118122-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/Makefile | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -88,10 +88,10 @@ else
KBUILD_CFLAGS += -m64

# Align jump targets to 1 byte, not the default 16 bytes:
- KBUILD_CFLAGS += -falign-jumps=1
+ KBUILD_CFLAGS += $(call cc-option,-falign-jumps=1)

# Pack loops tightly as well:
- KBUILD_CFLAGS += -falign-loops=1
+ KBUILD_CFLAGS += $(call cc-option,-falign-loops=1)

# Don't autogenerate traditional x87 instructions
KBUILD_CFLAGS += $(call cc-option,-mno-80387)