On 27.05.2013 20:47, Richard Henderson wrote:
> On 2013-05-27 04:43, Claudio Fontana wrote:
>>> Hmm, true. Although I'd been thinking more along the lines of
>>> arranging the code such that we'd use movz to set the zero.
>>
>> I think we need to keep treating zero specially if we want to keep the
>> optimization where we don't emit needless MOVK instructions for half-words
>> of value 0000h.
>>
>> I can however make one single function out of movi32 and movi64, it could
>> look like this:
>>
>> if (!value) {
>> tcg_out_movr(s, 0, rd, TCG_REG_ZXR);
>> return;
>> }
>>
>> base = (value > 0xffffffff) ? 0xd2800000 : 0x52800000;
>>
>> while (value) {
>> /* etc etc */
>> }
>
>
> if (type == TCG_TYPE_I32) {
> value = (uint32_t)value;
> ext = 0;
> } else if (value <= 0xffffffff) {
> ext = 0;
> } else {
> ext = 0x80000000;
> }
The check for type is probably unnecessary, since we don't gain anything (we
still have to check something once), so I'd rather use a uint64_t parameter and
then just check for value < 0xffffffff.
>
> base = 0x52800000; /* MOVZ */
> do {
> int shift = ctz64(value) & (63 & -16);
> int half = (value >> shift) & 0xffff;
> tcg_out32(s, base | ext | half << 5 | rd);
> value &= ~(0xffffUL << shift);
> base = 0x72800000; /* MOVK */
> } while (value != 0);
>
>
> Since we go through the loop at least once, we emit the movz for zero input.
> No need for any extra tests. And using ctz we can iterate fewer times.
Of course, doh. I'll make use of do..while.
Thanks,
Claudio
