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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 01/10] x86, bitops: remove use of "sbb" to return CF
@ 2016-06-07 23:31 H. Peter Anvin
  2016-06-07 23:39 ` [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>

Use SETC instead of SBB to return the value of CF from assembly. Using
SETcc enables uniformity with other flags-returning pieces of assembly
code.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
 arch/x86/include/asm/bitops.h      | 24 ++++++++++++------------
 arch/x86/include/asm/percpu.h      | 12 ++++++------
 arch/x86/include/asm/signal.h      |  6 +++---
 arch/x86/include/asm/sync_bitops.h | 18 +++++++++---------
 arch/x86/kernel/vm86_32.c          |  5 +----
 5 files changed, 31 insertions(+), 34 deletions(-)

diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 7766d1c..b2b797d 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -230,11 +230,11 @@ test_and_set_bit_lock(long nr, volatile unsigned long *addr)
  */
 static __always_inline int __test_and_set_bit(long nr, volatile unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
 	asm("bts %2,%1\n\t"
-	    "sbb %0,%0"
-	    : "=r" (oldbit), ADDR
+	    "setc %0"
+	    : "=qm" (oldbit), ADDR
 	    : "Ir" (nr));
 	return oldbit;
 }
@@ -270,11 +270,11 @@ static __always_inline int test_and_clear_bit(long nr, volatile unsigned long *a
  */
 static __always_inline int __test_and_clear_bit(long nr, volatile unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
 	asm volatile("btr %2,%1\n\t"
-		     "sbb %0,%0"
-		     : "=r" (oldbit), ADDR
+		     "setc %0"
+		     : "=qm" (oldbit), ADDR
 		     : "Ir" (nr));
 	return oldbit;
 }
@@ -282,11 +282,11 @@ static __always_inline int __test_and_clear_bit(long nr, volatile unsigned long
 /* WARNING: non atomic and it can be reordered! */
 static __always_inline int __test_and_change_bit(long nr, volatile unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
 	asm volatile("btc %2,%1\n\t"
-		     "sbb %0,%0"
-		     : "=r" (oldbit), ADDR
+		     "setc %0"
+		     : "=qm" (oldbit), ADDR
 		     : "Ir" (nr) : "memory");
 
 	return oldbit;
@@ -313,11 +313,11 @@ static __always_inline int constant_test_bit(long nr, const volatile unsigned lo
 
 static __always_inline int variable_test_bit(long nr, volatile const unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
 	asm volatile("bt %2,%1\n\t"
-		     "sbb %0,%0"
-		     : "=r" (oldbit)
+		     "setc %0"
+		     : "=qm" (oldbit)
 		     : "m" (*(unsigned long *)addr), "Ir" (nr));
 
 	return oldbit;
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index e0ba66c..65039e9 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -510,9 +510,9 @@ do {									\
 /* This is not atomic against other CPUs -- CPU preemption needs to be off */
 #define x86_test_and_clear_bit_percpu(bit, var)				\
 ({									\
-	int old__;							\
-	asm volatile("btr %2,"__percpu_arg(1)"\n\tsbbl %0,%0"		\
-		     : "=r" (old__), "+m" (var)				\
+	unsigned char old__;						\
+	asm volatile("btr %2,"__percpu_arg(1)"\n\tsetc %0"		\
+		     : "=qm" (old__), "+m" (var)			\
 		     : "dIr" (bit));					\
 	old__;								\
 })
@@ -532,11 +532,11 @@ static __always_inline int x86_this_cpu_constant_test_bit(unsigned int nr,
 static inline int x86_this_cpu_variable_test_bit(int nr,
                         const unsigned long __percpu *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
 	asm volatile("bt "__percpu_arg(2)",%1\n\t"
-			"sbb %0,%0"
-			: "=r" (oldbit)
+			"setc %0"
+			: "=qm" (oldbit)
 			: "m" (*(unsigned long *)addr), "Ir" (nr));
 
 	return oldbit;
diff --git a/arch/x86/include/asm/signal.h b/arch/x86/include/asm/signal.h
index 2138c9a..dd1e7d6 100644
--- a/arch/x86/include/asm/signal.h
+++ b/arch/x86/include/asm/signal.h
@@ -81,9 +81,9 @@ static inline int __const_sigismember(sigset_t *set, int _sig)
 
 static inline int __gen_sigismember(sigset_t *set, int _sig)
 {
-	int ret;
-	asm("btl %2,%1\n\tsbbl %0,%0"
-	    : "=r"(ret) : "m"(*set), "Ir"(_sig-1) : "cc");
+	unsigned char ret;
+	asm("btl %2,%1\n\tsetc %0"
+	    : "=qm"(ret) : "m"(*set), "Ir"(_sig-1) : "cc");
 	return ret;
 }
 
diff --git a/arch/x86/include/asm/sync_bitops.h b/arch/x86/include/asm/sync_bitops.h
index f28a24b..cbf8847 100644
--- a/arch/x86/include/asm/sync_bitops.h
+++ b/arch/x86/include/asm/sync_bitops.h
@@ -79,10 +79,10 @@ static inline void sync_change_bit(long nr, volatile unsigned long *addr)
  */
 static inline int sync_test_and_set_bit(long nr, volatile unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
-	asm volatile("lock; bts %2,%1\n\tsbbl %0,%0"
-		     : "=r" (oldbit), "+m" (ADDR)
+	asm volatile("lock; bts %2,%1\n\tsetc %0"
+		     : "=qm" (oldbit), "+m" (ADDR)
 		     : "Ir" (nr) : "memory");
 	return oldbit;
 }
@@ -97,10 +97,10 @@ static inline int sync_test_and_set_bit(long nr, volatile unsigned long *addr)
  */
 static inline int sync_test_and_clear_bit(long nr, volatile unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
-	asm volatile("lock; btr %2,%1\n\tsbbl %0,%0"
-		     : "=r" (oldbit), "+m" (ADDR)
+	asm volatile("lock; btr %2,%1\n\tsetc %0"
+		     : "=qm" (oldbit), "+m" (ADDR)
 		     : "Ir" (nr) : "memory");
 	return oldbit;
 }
@@ -115,10 +115,10 @@ static inline int sync_test_and_clear_bit(long nr, volatile unsigned long *addr)
  */
 static inline int sync_test_and_change_bit(long nr, volatile unsigned long *addr)
 {
-	int oldbit;
+	unsigned char oldbit;
 
-	asm volatile("lock; btc %2,%1\n\tsbbl %0,%0"
-		     : "=r" (oldbit), "+m" (ADDR)
+	asm volatile("lock; btc %2,%1\n\tsetc %0"
+		     : "=qm" (oldbit), "+m" (ADDR)
 		     : "Ir" (nr) : "memory");
 	return oldbit;
 }
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 3dce1ca..01f30e5 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -440,10 +440,7 @@ static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
 
 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
 {
-	__asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
-		:"=r" (nr)
-		:"m" (*bitmap), "r" (nr));
-	return nr;
+	return test_bit(nr, bitmap->__map);
 }
 
 #define val_byte(val, n) (((__u8 *)&val)[n])
-- 
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 01/10] x86, bitops: remove use of "sbb" to return CF H. Peter Anvin
2016-06-07 23:39 ` [tip:x86/asm] " tip-bot for H. Peter Anvin

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