Some issues to resolve with XFree 4.0 yet

[Franz Sirl]

At 12:45 29.03.00, Gabriel Paubert wrote:
>BTW, did anybody think of adding a __builtin_byteswap to GCC ?
>
>This would allow the compiler to directly generate *brx instructions on
>PPC by combining them with memory loads and stores. I'm aware that it
>would require an additional constraint letter for indexed addressing modee
>only but this is required for Altivec anyway.
>
>And this would open opportunities for quite a lot of optimizations, for
>example when setting or clearing some bits in a device register. In this
>latter case (and in the given example) operands are often constants and
>the compiler could generate non byte swapped load and stores and byte swap
>the constants.

Hmm, I was thinking about adding __attribute__((little_endian)) and
__attribute__((big_endian)) to further describe variables. This should give
us optimum optimization on various platforms. Even things like:

union {
         unsigned long little_var __attribute__((little_endian));
         unsigned long big_var __attribute__((big_endian));
}

should be possible then.

Franz.


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