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

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>

diff --git a/src/arch/i386/include/bits/byteswap.h b/src/arch/i386/include/bits/byteswap.h
index d40771354b46da823b3cebb33bdf6238754637d2..f3d30a254178e53bf7648fb2e97504589d48c7f0 100644 (file)
--- a/src/arch/i386/include/bits/byteswap.h
+++ b/src/arch/i386/include/bits/byteswap.h
@@ -19,7 +19,7 @@ __bswap_variable_16 ( uint16_t x ) {
 
 static inline __attribute__ (( always_inline )) void
 __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
@@ -63,9 +63,8 @@ __bswap_64s ( uint64_t *x ) {
                  "xchgl %2,%1\n\t"
                  "bswapl %2\n\t"
                  "movl %2,%0\n\t"
-                 : "=g" ( dwords->low ), "=g" ( dwords->high ),
-                   "=r" ( discard )
-                 : "0" ( dwords->low ), "1" ( dwords->high ) );
+                 : "+m" ( dwords->low ), "+m" ( dwords->high ),
+                   "=r" ( discard ) );
 }
 
 #endif /* _BITS_BYTESWAP_H */