At 14:33 07.12.2006 +0100, Fabian Cenedese wrote:
>Hi
>
>Is there a flag to tell gcc NOT to use float assembler commands
>for 64bit data? We have problems that the generated code contains
>float commands while the target (partially) has no float support.
>
>To make it clear: This is not about the soft-float library which would
>emulate float commands. We don't want gcc to even generate
>those unless it really is about float operations.
>
>Here's one example (for PPC603), but there also are others:
>
>inline uint64 GetSystemTicks()
>{
> union {
> uint64 s;
> struct {
> uint32 high;
> uint32 low;
> } m;
> } result;
>
> uint32 tmp=0;
> asm volatile (
> "mftbu %0" "\n\t"
> "mftb %1" "\n\t"
> "mftbu %2" "\n\t"
> "cmpw %3,%4" "\n\t"
> "beq 0f" "\n\t"
> "mftbu %0" "\n\t"
> "mftb %1" "\n\t"
> "0:"
> : "=r" (result.m.high), "=r" (result.m.low), "=r" (tmp)
> : "0" (result.m.high), "2" (tmp));
>
> return result.s;
>}
>
>...(snip)...
> mr 0,10 # tmp120,
> stw 0,8(31) # result.m.high, tmp120
> stw 9,12(31) # result.m.low, tmp121
> stw 11,16(31) # tmp, tmp122
>-> lfd 0,8(31) # result.s, result.s
>-> stfd 0,24(31) #, result.s
> lwz 9,24(31) #, <result>
> lwz 10,28(31) #, <result>
> mr 3,9 # <result>, <result>
> mr 4,10 # <result>, <result>
> lwz 11,0(1) #,
> lwz 31,-4(11) #,
> mr 1,11 #,
> blr #
>
>The float commands are simply used for moving 64 bit of data around.
>That may be faster than 2x32 but not working here. I'm interested in
>workarounds for various gcc versions (2.95, 3.4, 4.x).
Doesn't anybody know a way around this? Or has the same problem?
The issue is not new as seen here:
http://gcc.gnu.org/ml/gcc-help/2000-10/msg00166.html
http://gcc.gnu.org/ml/gcc-bugs/2000-10/msg00546.html
Thanks for any ideas (even changing gcc source code).
bye Fabi
