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* [PATCH v2 00/10] x86: use gcc 6+ asm flag output feature
@ 2016-06-08 19:38 H. Peter Anvin
  2016-06-08 19:38 ` [PATCH v2 01/10] x86, bitops: remove use of "sbb" to return CF H. Peter Anvin
                   ` (10 more replies)
  0 siblings, 11 replies; 24+ messages in thread
From: H. Peter Anvin @ 2016-06-08 19:38 UTC (permalink / raw)
  To: Ingo Molnar, Thomas Gleixner, H. Peter Anvin, Linux Kernel Mailing List
  Cc: Andy Lutomirski, Borislav Petkov

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

v2: fix a conflict between <linux/random.h> and <asm/archrandom.h>
    discovered by Ingo Molnar.  There are a few places in x86-specific
    code where we need all of <arch/archrandom.h> even when
    xCONFIG_ARCH_RANDOM is disabled, so <linux/random.h> does not
    suffice.  Only the <asm/archrandom.h> patch has been changed;
    since it is a little bit different from the others I have moved it
    to the end.

^ permalink raw reply	[flat|nested] 24+ messages in thread
* [PATCH 08/10] x86, asm: Use CC_SET()/CC_OUT() in <asm/rwsem.h>
@ 2016-06-07 23:31 H. Peter Anvin
  2016-06-07 23:42 ` [tip:x86/asm] " tip-bot for H. Peter Anvin
  0 siblings, 1 reply; 24+ messages in thread
From: H. Peter Anvin @ 2016-06-07 23:31 UTC (permalink / raw)
  To: Ingo Molnar, Thomas Gleixner, H. Peter Anvin, Linux Kernel Mailing List
  Cc: Peter Zijlstra, Andy Lutomirski, Borislav Petkov

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

Remove open-coded uses of set instructions to use CC_SET()/CC_OUT() in
<asm/rwsem.h>.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
 arch/x86/include/asm/rwsem.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index c508770..1e8be26 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -149,10 +149,10 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem)
 		     LOCK_PREFIX "  cmpxchg  %2,%0\n\t"
 		     "  jnz	     1b\n\t"
 		     "2:\n\t"
-		     "  sete         %3\n\t"
+		     CC_SET(e)
 		     "# ending __down_write_trylock\n\t"
 		     : "+m" (sem->count), "=&a" (tmp0), "=&r" (tmp1),
-		       "=qm" (result)
+		       CC_OUT(e) (result)
 		     : "er" (RWSEM_ACTIVE_WRITE_BIAS)
 		     : "memory", "cc");
 	return result;
-- 
2.7.3.0.11.gd79db92

^ permalink raw reply related	[flat|nested] 24+ messages in thread

end of thread, other threads:[~2016-06-09 15:49 UTC | newest]

Thread overview: 24+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-06-08 19:38 [PATCH v2 00/10] x86: use gcc 6+ asm flag output feature H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 01/10] x86, bitops: remove use of "sbb" to return CF H. Peter Anvin
2016-06-08 19:45   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 02/10] x86, asm: use bool for bitops and other assembly outputs H. Peter Anvin
2016-06-08 19:46   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 03/10] x86, asm: change the GEN_*_RMWcc() macros to not quote the condition H. Peter Anvin
2016-06-08 19:46   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 04/10] x86, asm: define CC_SET() and CC_OUT() macros H. Peter Anvin
2016-06-08 19:47   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 05/10] x86, asm: change GEN_*_RMWcc() to use CC_SET()/CC_OUT() H. Peter Anvin
2016-06-08 19:47   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 06/10] x86, asm: Use CC_SET()/CC_OUT() in <asm/bitops.h> H. Peter Anvin
2016-06-08 19:48   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 07/10] x86, asm: Use CC_SET()/CC_OUT() in <asm/percpu.h> H. Peter Anvin
2016-06-08 19:48   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 08/10] x86, asm: Use CC_SET()/CC_OUT() in <asm/rwsem.h> H. Peter Anvin
2016-06-08 19:49   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 09/10] x86, asm, boot: Use CC_SET()/CC_OUT() in arch/x86/boot/boot.h H. Peter Anvin
2016-06-08 19:49   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-08 19:38 ` [PATCH v2 10/10] x86, asm: Use CC_SET()/CC_OUT() and static_cpu_has() in archrandom.h H. Peter Anvin
2016-06-08 19:49   ` [tip:x86/asm] " tip-bot for H. Peter Anvin
2016-06-09 15:49   ` [PATCH v2 10/10] " Borislav Petkov
2016-06-08 21:30 ` [PATCH v2 00/10] x86: use gcc 6+ asm flag output feature H. Peter Anvin
  -- strict thread matches above, loose matches on Subject: below --
2016-06-07 23:31 [PATCH 08/10] x86, asm: Use CC_SET()/CC_OUT() in <asm/rwsem.h> H. Peter Anvin
2016-06-07 23:42 ` [tip:x86/asm] " tip-bot for H. Peter Anvin

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