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Commit 0c44c2d0 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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x86: Use asm goto to implement better modify_and_test() functions 

Linus suggested using asm goto to get rid of the typical SETcc + TEST
instruction pair -- which also clobbers an extra register -- for our
typical modify_and_test() functions.

Because asm goto doesn't allow output fields it has to include an
unconditinal memory clobber when it changes a memory variable to force
a reload.

Luckily all atomic ops already imply a compiler barrier to go along
with their memory barrier semantics.
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-0mtn9siwbeo1d33bap1422se@git.kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 43148951
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Inline Side-by-side
Showing with 58 additions and 92 deletions
arch/x86/include/asm/atomic.h
View file @ 0c44c2d0
......@@ -6,6 +6,7 @@
#include <asm/processor.h>
#include <asm/alternative.h>
#include <asm/cmpxchg.h>
#include <asm/rmwcc.h>
/*
* Atomic operations that C can't guarantee us. Useful for
......@@ -76,12 +77,7 @@ static inline void atomic_sub(int i, atomic_t *v)
*/
static inline int atomic_sub_and_test(int i, atomic_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "subl %2,%0; sete %1"
: "+m" (v->counter), "=qm" (c)
: "ir" (i) : "memory");
return c;
GEN_BINARY_RMWcc(LOCK_PREFIX "subl", v->counter, i, "%0", "e");
}
/**
......@@ -118,12 +114,7 @@ static inline void atomic_dec(atomic_t *v)
*/
static inline int atomic_dec_and_test(atomic_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "decl %0; sete %1"
: "+m" (v->counter), "=qm" (c)
: : "memory");
return c != 0;
GEN_UNARY_RMWcc(LOCK_PREFIX "decl", v->counter, "%0", "e");
}
/**
......@@ -136,12 +127,7 @@ static inline int atomic_dec_and_test(atomic_t *v)
*/
static inline int atomic_inc_and_test(atomic_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "incl %0; sete %1"
: "+m" (v->counter), "=qm" (c)
: : "memory");
return c != 0;
GEN_UNARY_RMWcc(LOCK_PREFIX "incl", v->counter, "%0", "e");
}
/**
......@@ -155,12 +141,7 @@ static inline int atomic_inc_and_test(atomic_t *v)
*/
static inline int atomic_add_negative(int i, atomic_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "addl %2,%0; sets %1"
: "+m" (v->counter), "=qm" (c)
: "ir" (i) : "memory");
return c;
GEN_BINARY_RMWcc(LOCK_PREFIX "addl", v->counter, i, "%0", "s");
}
/**
......
arch/x86/include/asm/atomic64_64.h
View file @ 0c44c2d0
......@@ -72,12 +72,7 @@ static inline void atomic64_sub(long i, atomic64_t *v)
*/
static inline int atomic64_sub_and_test(long i, atomic64_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "subq %2,%0; sete %1"
: "=m" (v->counter), "=qm" (c)
: "er" (i), "m" (v->counter) : "memory");
return c;
GEN_BINARY_RMWcc(LOCK_PREFIX "subq", v->counter, i, "%0", "e");
}
/**
......@@ -116,12 +111,7 @@ static inline void atomic64_dec(atomic64_t *v)
*/
static inline int atomic64_dec_and_test(atomic64_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "decq %0; sete %1"
: "=m" (v->counter), "=qm" (c)
: "m" (v->counter) : "memory");
return c != 0;
GEN_UNARY_RMWcc(LOCK_PREFIX "decq", v->counter, "%0", "e");
}
/**
......@@ -134,12 +124,7 @@ static inline int atomic64_dec_and_test(atomic64_t *v)
*/
static inline int atomic64_inc_and_test(atomic64_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "incq %0; sete %1"
: "=m" (v->counter), "=qm" (c)
: "m" (v->counter) : "memory");
return c != 0;
GEN_UNARY_RMWcc(LOCK_PREFIX "incq", v->counter, "%0", "e");
}
/**
......@@ -153,12 +138,7 @@ static inline int atomic64_inc_and_test(atomic64_t *v)
*/
static inline int atomic64_add_negative(long i, atomic64_t *v)
{
unsigned char c;
asm volatile(LOCK_PREFIX "addq %2,%0; sets %1"
: "=m" (v->counter), "=qm" (c)
: "er" (i), "m" (v->counter) : "memory");
return c;
GEN_BINARY_RMWcc(LOCK_PREFIX "addq", v->counter, i, "%0", "s");
}
/**
......
arch/x86/include/asm/bitops.h
View file @ 0c44c2d0
......@@ -14,6 +14,7 @@
#include <linux/compiler.h>
#include <asm/alternative.h>
#include <asm/rmwcc.h>
#if BITS_PER_LONG == 32
# define _BITOPS_LONG_SHIFT 5
......@@ -204,12 +205,7 @@ static inline void change_bit(long nr, volatile unsigned long *addr)
*/
static inline int test_and_set_bit(long nr, volatile unsigned long *addr)
{
int oldbit;
asm volatile(LOCK_PREFIX "bts %2,%1\n\t"
"sbb %0,%0" : "=r" (oldbit), ADDR : "Ir" (nr) : "memory");
return oldbit;
GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, nr, "%0", "c");
}
/**
......@@ -255,13 +251,7 @@ static inline int __test_and_set_bit(long nr, volatile unsigned long *addr)
*/
static inline int test_and_clear_bit(long nr, volatile unsigned long *addr)
{
int oldbit;
asm volatile(LOCK_PREFIX "btr %2,%1\n\t"
"sbb %0,%0"
: "=r" (oldbit), ADDR : "Ir" (nr) : "memory");
return oldbit;
GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, nr, "%0", "c");
}
/**
......@@ -314,13 +304,7 @@ static inline int __test_and_change_bit(long nr, volatile unsigned long *addr)
*/
static inline int test_and_change_bit(long nr, volatile unsigned long *addr)
{
int oldbit;
asm volatile(LOCK_PREFIX "btc %2,%1\n\t"
"sbb %0,%0"
: "=r" (oldbit), ADDR : "Ir" (nr) : "memory");
return oldbit;
GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, nr, "%0", "c");
}
static __always_inline int constant_test_bit(long nr, const volatile unsigned long *addr)
......
arch/x86/include/asm/local.h
View file @ 0c44c2d0
......@@ -52,12 +52,7 @@ static inline void local_sub(long i, local_t *l)
*/
static inline int local_sub_and_test(long i, local_t *l)
{
unsigned char c;
asm volatile(_ASM_SUB "%2,%0; sete %1"
: "+m" (l->a.counter), "=qm" (c)
: "ir" (i) : "memory");
return c;
GEN_BINARY_RMWcc(_ASM_SUB, l->a.counter, i, "%0", "e");
}
/**
......@@ -70,12 +65,7 @@ static inline int local_sub_and_test(long i, local_t *l)
*/
static inline int local_dec_and_test(local_t *l)
{
unsigned char c;
asm volatile(_ASM_DEC "%0; sete %1"
: "+m" (l->a.counter), "=qm" (c)
: : "memory");
return c != 0;
GEN_UNARY_RMWcc(_ASM_DEC, l->a.counter, "%0", "e");
}
/**
......@@ -88,12 +78,7 @@ static inline int local_dec_and_test(local_t *l)
*/
static inline int local_inc_and_test(local_t *l)
{
unsigned char c;
asm volatile(_ASM_INC "%0; sete %1"
: "+m" (l->a.counter), "=qm" (c)
: : "memory");
return c != 0;
GEN_UNARY_RMWcc(_ASM_INC, l->a.counter, "%0", "e");
}
/**
......@@ -107,12 +92,7 @@ static inline int local_inc_and_test(local_t *l)
*/
static inline int local_add_negative(long i, local_t *l)
{
unsigned char c;
asm volatile(_ASM_ADD "%2,%0; sets %1"
: "+m" (l->a.counter), "=qm" (c)
: "ir" (i) : "memory");
return c;
GEN_BINARY_RMWcc(_ASM_ADD, l->a.counter, i, "%0", "s");
}
/**
......
arch/x86/include/asm/rmwcc.h 0 → 100644
View file @ 0c44c2d0
#ifndef _ASM_X86_RMWcc
#define _ASM_X86_RMWcc
#ifdef CC_HAVE_ASM_GOTO
#define __GEN_RMWcc(fullop, var, cc, ...) \
do { \
asm volatile goto (fullop "; j" cc " %l[cc_label]" \
: : "m" (var), ## __VA_ARGS__ \
: "memory" : cc_label); \
return 0; \
cc_label: \
return 1; \
} while (0)
#define GEN_UNARY_RMWcc(op, var, arg0, cc) \
__GEN_RMWcc(op " " arg0, var, cc)
#define GEN_BINARY_RMWcc(op, var, val, arg0, cc) \
__GEN_RMWcc(op " %1, " arg0, var, cc, "er" (val))
#else /* !CC_HAVE_ASM_GOTO */
#define __GEN_RMWcc(fullop, var, cc, ...) \
do { \
char c; \
asm volatile (fullop "; set" cc " %1" \
: "+m" (var), "=qm" (c) \
: __VA_ARGS__ : "memory"); \
return c != 0; \
} while (0)
#define GEN_UNARY_RMWcc(op, var, arg0, cc) \
__GEN_RMWcc(op " " arg0, var, cc)
#define GEN_BINARY_RMWcc(op, var, val, arg0, cc) \
__GEN_RMWcc(op " %2, " arg0, var, cc, "er" (val))
#endif /* CC_HAVE_ASM_GOTO */
#endif /* _ASM_X86_RMWcc */
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