[pulseaudio-discuss] [PATCH 06/10] core: Add ARM NEON optimized remapping code

[Tanu Kaskinen]

On 03/29/2013 05:56 PM, Peter Meerwald wrote:
> +static inline void mono_to_stereo_float_neon_a9(float *dst, const float *src, unsigned n) {
> +    int i = n&  1;
> +
> +    __asm__ __volatile__ (
> +        "movs       %[n], %[n], lsr #1      \n\t"
> +        "beq        2f                      \n\t"
> +
> +        "1:                                 \n\t"
> +        "ldm        %[src]!, {r4,r6}        \n\t"
> +        "mov        r5, r4                  \n\t"
> +        "mov        r7, r6                  \n\t"
> +        "subs       %[n], %[n], #1          \n\t"
> +        "stm        %[dst]!, {r4-r7}        \n\t"
> +        "bgt        1b                      \n\t"
> +
> +        "2:                                 \n\t"
> +
> +        : [dst] "+r" (dst), [src] "+r" (src), [n] "+r" (n) /* output operands (or input operands that get modified) */
> +        : /* input operands */
> +        : "memory", "cc", "r4", "r5", "r6", "r7" /* clobber list */
> +    );

Could you add a comment explaining why we have separate implementations 
for A8 and A9? Also, this isn't NEON code at all, is it? So perhaps the 
function name should be mono_to_stereo_float_generic_arm or something 
like that.

> +static void init_remap_neon(pa_remap_t *m) {
> +    unsigned n_oc, n_ic;
> +
> +    n_oc = m->o_ss->channels;
> +    n_ic = m->i_ss->channels;
> +
> +    /* find some common channel remappings, fall back to full matrix operation. */
> +    if (n_ic == 1&&  n_oc == 2&&
> +            m->map_table_i[0][0] == PA_VOLUME_NORM&&  m->map_table_i[1][0] == PA_VOLUME_NORM) {
> +        if (arm_flags&  PA_CPU_ARM_CORTEX_A8) {
> +            m->do_remap = (pa_do_remap_func_t) remap_mono_to_stereo_neon_a8;
> +            pa_log_info("Using ARM NEON/A8 mono to stereo remapping");
> +        }
> +        else {
> +            m->do_remap = (pa_do_remap_func_t) remap_mono_to_stereo_neon_a9;
> +            pa_log_info("Using ARM NEON/A9 mono to stereo remapping");

This log message is incorrect, if I'm right in that the code in 
remap_mono_to_stereo_neon_a9() isn't NEON code.

The remapping code looks correct, thanks for this work!

-- 
Tanu