_byteswap_ulong
_byteswap_uint64
Both in current Whidbey builds.
#include <intrin.h>
int main()
{
volatile unsigned long l = 1;
volatile unsigned long long ll = 1;
l = _byteswap_ulong(l);
ll = _byteswap_uint64(ll);
}
in a release build gives you
PUBLIC _main
; Function compile flags: /Ogtpy
; File d:\documents and settings\ronaldl\my documents\visual studio
2005\projects\byteswap\byteswap.cpp
; COMDAT _main
_TEXT SEGMENT
_l$ = -12 ; size = 4
_ll$ = -8 ; size = 8
_main PROC ; COMDAT
; 8 : {
sub esp, 12 ; 0000000cH
; 9 : volatile unsigned long l = 1;
mov eax, 1
mov DWORD PTR _l$[esp+12], eax
; 10 : volatile unsigned long long ll = 1;
mov DWORD PTR _ll$[esp+12], eax
mov DWORD PTR _ll$[esp+16], 0
; 11 :
; 12 : l = _byteswap_ulong(l);
mov eax, DWORD PTR _l$[esp+12]
bswap eax
mov DWORD PTR _l$[esp+12], eax
; 13 : ll = _byteswap_uint64(ll);
mov ecx, DWORD PTR _ll$[esp+12]
mov edx, DWORD PTR _ll$[esp+16]
bswap edx
bswap ecx
mov DWORD PTR _ll$[esp+12], edx
mov DWORD PTR _ll$[esp+16], ecx
; 14 : }
xor eax, eax
add esp, 12 ; 0000000cH
ret 0
_main ENDP
_TEXT ENDS
END
Or for X64 which has a quadword bswap instruction:
Function compile flags: /Ogtpy
; File d:\documents and settings\ronaldl\my documents\visual studio
2005\projects\byteswap\byteswap.cpp
; COMDAT main
_TEXT SEGMENT
l$ = 8
ll$ = 16
main PROC ; COMDAT
; 9 : volatile unsigned long l = 1;
mov DWORD PTR l$[rsp], 1
; 10 : volatile unsigned long long ll = 1;
mov QWORD PTR ll$[rsp], 1
; 11 :
; 12 : l = _byteswap_ulong(l);
mov eax, DWORD PTR l$[rsp]
bswap eax
mov DWORD PTR l$[rsp], eax
; 13 : ll = _byteswap_uint64(ll);
mov rax, QWORD PTR ll$[rsp]
bswap rax
mov QWORD PTR ll$[rsp], rax
; 14 : }
xor eax, eax
ret 0
main ENDP
_TEXT ENDS
END
Ronald Laeremans
Visual C++ team
"Carl Daniel [VC++ MVP]" <cp*****************************@mvps.org.nospam >
wrote in message news:eI**************@TK2MSFTNGP09.phx.gbl...
George M. Garner Jr. wrote: Is there an intrinsic to wrap the bswap x86 instruction. I have
written a function to do this with inline assembler but I am
wondering if an intrinsic wouldn't be a better solution.
it would be. AFIAK there is no such intrinsic.
-cd
