On 09/05/2013 06:32 AM, Claudio Fontana wrote:
>> {
>> - uint32_t half, base, shift, movk = 0;
>> - /* construct halfwords of the immediate with MOVZ/MOVK with LSL */
>> - /* using MOVZ 0x52800000 | extended reg.. */
>> - base = (value > 0xffffffff) ? 0xd2800000 : 0x52800000;
>> - /* count trailing zeros in 16 bit steps, mapping 64 to 0. Emit the
>> - first MOVZ with the half-word immediate skipping the zeros, with a
>> shift
>> - (LSL) equal to this number. Then morph all next instructions into
>> MOVKs.
>> - Zero the processed half-word in the value, continue until empty.
>> - We build the final result 16bits at a time with up to 4 instructions,
>> - but do not emit instructions for 16bit zero holes. */
>
> Please do not remove these comments.
> In my judgement this part of the code profits from some verbose clarification.
> What is happening might be obvious to you, but not to others trying to step
> in.
Fair enough.
> In general I'd prefer to keep movi as it was (functionally-wise) for the
> time being, replacing it with a more efficient version once we can get some
> numbers (which will be soon) with which to justify (or not) the added code
> complexity.
The most important thing we're not doing at the moment is handling negative
numbers efficiently. E.g. we're using 4 insns to load -1.
r~
