[PATCH 00/10] x86: use gcc 6+ asm flag output feature

From	"H. Peter Anvin" <hpa@linux.intel.com>
Newsgroups	linux.kernel
Subject	[PATCH 00/10] x86: use gcc 6+ asm flag output feature
Date	2016-06-08 01:40 +0200
Message-ID	<rHyLf-GT-5@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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From: "H. Peter Anvin" <hpa@zytor.com>

gcc 6+ has the ability to let flags (actually, conditions, which are
specific combinations of flags) to be used directly as asm() outputs.
The syntax for that is "=@cc<cc>" where <cc> is the same set of
letters that would be used in a j<cc> or set<cc> instruction
(e.g. "=@ccz" to test the ZF flag.)

This patchset by itself reduces the size of the x86-64 kernel by
0.12%, from a baseline of 4.7-rc2 built with gcc 6.1 (first line is
with the patchset, the second one is without):

     text       data       bss        dec       hex filename
     
 68245656   41004339  20533248  129783243   7bc55cb o.i386-allconfig/vmlinux
 68355716   41008499  20533248  129897463   7be13f7 o.i386-allconfig/vmlinux

127384005  129742359  38150144  295276508  11998fdc o.x86_64-allconfig/vmlinux
127538765  129742295  38150144  295431204  119bec24 o.x86_64-allconfig/vmlinux

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[PATCH 00/10] x86: use gcc 6+ asm flag output feature "H. Peter Anvin" <hpa@linux.intel.com> - 2016-06-08 01:40 +0200
  [PATCH 10/10] x86, asm, boot: Use CC_SET()/CC_OUT() in arch/x86/boot/boot.h "H. Peter Anvin" <hpa@linux.intel.com> - 2016-06-08 01:40 +0200
    [tip:x86/asm] x86, asm, boot: Use CC_SET()/CC_OUT() in  arch/x86/boot/boot.h "tip-bot for H. Peter Anvin" <tipbot@zytor.com> - 2016-06-08 01:50 +0200
  Re: [PATCH 00/10] x86: use gcc 6+ asm flag output feature Peter Zijlstra <peterz@infradead.org> - 2016-06-08 10:10 +0200
    Re: [PATCH 00/10] x86: use gcc 6+ asm flag output feature "H. Peter Anvin" <hpa@zytor.com> - 2016-06-08 11:00 +0200

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