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[i386] Use memory address constraints in __bswap_16s() and __bswap_64s()

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Minimise code size by forcing the use of memory addresses for
__bswap_16s() and __bswap_64s().  (__bswap_32s() cannot avoid loading the
value into a register.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2012-03-04 21:41:24 +00:00
parent e187de7239
commit 732bea2f88
1 changed files with 3 additions and 4 deletions
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7
src/arch/i386/include/bits/byteswap.h
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@@ -19,7 +19,7 @@ __bswap_variable_16 ( uint16_t x ) {
static inline __attribute__ (( always_inline )) void static inline __attribute__ (( always_inline )) void
__bswap_16s ( uint16_t *x ) { __bswap_16s ( uint16_t *x ) {
__asm__ ( "rorw $8, %0" : "=g" ( *x ) : "0" ( *x ) ); __asm__ ( "rorw $8, %0" : "+m" ( *x ) );
} }
static inline __attribute__ (( always_inline, const )) uint32_t static inline __attribute__ (( always_inline, const )) uint32_t
@@ -63,9 +63,8 @@ __bswap_64s ( uint64_t *x ) {
"xchgl %2,%1\n\t" "xchgl %2,%1\n\t"
"bswapl %2\n\t" "bswapl %2\n\t"
"movl %2,%0\n\t" "movl %2,%0\n\t"
: "=g" ( dwords->low ), "=g" ( dwords->high ), : "+m" ( dwords->low ), "+m" ( dwords->high ),
"=r" ( discard ) "=r" ( discard ) );
: "0" ( dwords->low ), "1" ( dwords->high ) );
} }
#endif /* _BITS_BYTESWAP_H */ #endif /* _BITS_BYTESWAP_H */