linux-kernel - [PATCH 4.9 20/59] x86/kbuild: Use cc-option to enable -falign-{jumps/loops}

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Date:   Wed, 21 Nov 2018 20:06:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Matthias Kaehlcke <mka@...omium.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michael Davidson <md@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, grundler@...omium.org,
        Ingo Molnar <mingo@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 4.9 20/59] x86/kbuild: Use cc-option to enable -falign-{jumps/loops}

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Kaehlcke <mka@...omium.org>

commit 2c4fd1ac3ff167c91272dc43c7bfd2269ef61557 upstream.

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

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
Cc: Greg Hackmann <ghackmann@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Michael Davidson <md@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: grundler@...omium.org
Link: http://lkml.kernel.org/r/20170413172609.118122-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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)