On 3 November 2002 13:23, Martin J. Bligh wrote:
> > Here is the cure: force_inline will guarantee inlining.
> >
> > To use _only_ with functions which meant to be almost
> > optimized away to nothing but are large and gcc might decide
> > they are _too_ large for inlining.
>
> So aside from the ugliness of code, which one actually runs faster?
This can *never* run faster non-inlined because it is called with
n being compile time constant:
static inline void * __constant_memcpy(void * to, const void * from, size_t n)
{
switch (n) {
case 0:
return to;
case 1:
*(unsigned char *)to = *(const unsigned char *)from;
return to;
case 2:
*(unsigned short *)to = *(const unsigned short *)from;
return to;
case 3:
*(unsigned short *)to = *(const unsigned short *)from;
*(2+(unsigned char *)to) = *(2+(const unsigned char *)from);
return to;
case 4:
*(unsigned long *)to = *(const unsigned long *)from;
return to;
case 6: /* for Ethernet addresses */
*(unsigned long *)to = *(const unsigned long *)from;
*(2+(unsigned short *)to) = *(2+(const unsigned short *)from);
return to;
case 8:
*(unsigned long *)to = *(const unsigned long *)from;
*(1+(unsigned long *)to) = *(1+(const unsigned long *)from);
return to;
case 12:
*(unsigned long *)to = *(const unsigned long *)from;
*(1+(unsigned long *)to) = *(1+(const unsigned long *)from);
*(2+(unsigned long *)to) = *(2+(const unsigned long *)from);
return to;
case 16:
*(unsigned long *)to = *(const unsigned long *)from;
*(1+(unsigned long *)to) = *(1+(const unsigned long *)from);
*(2+(unsigned long *)to) = *(2+(const unsigned long *)from);
*(3+(unsigned long *)to) = *(3+(const unsigned long *)from);
return to;
case 20:
*(unsigned long *)to = *(const unsigned long *)from;
*(1+(unsigned long *)to) = *(1+(const unsigned long *)from);
*(2+(unsigned long *)to) = *(2+(const unsigned long *)from);
*(3+(unsigned long *)to) = *(3+(const unsigned long *)from);
*(4+(unsigned long *)to) = *(4+(const unsigned long *)from);
return to;
}
#define COMMON(x) \
__asm__ __volatile__( \
"rep ; movsl" \
x \
: "=&c" (d0), "=&D" (d1), "=&S" (d2) \
: "0" (n/4),"1" ((long) to),"2" ((long) from) \
: "memory");
{
int d0, d1, d2;
switch (n % 4) {
case 0: COMMON(""); return to;
case 1: COMMON("\n\tmovsb"); return to;
case 2: COMMON("\n\tmovsw"); return to;
default: COMMON("\n\tmovsw\n\tmovsb"); return to;
}
}
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This archive was generated by hypermail 2b29 : Thu Nov 07 2002 - 22:00:30 EST