[pulseaudio-discuss] [PATCH v3] netbsd: Stop depending upon nonstandard __WORDSIZE

[Kamil Rytarowski]

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On 16.12.2015 11:02, Pali Rohár wrote:
> On Wednesday 16 December 2015 10:40:05 Kamil Rytarowski wrote:
>> There is no way to check CPU type in a portable way across ABIs.
>> 
>> Go for pa_mult_s16_volume() version without need for int64_t. 
>> It's actually the same as in src/tests/mult-s16-test.c.
>> 
>> This change fixes build on NetBSD. --- 
>> src/pulsecore/sample-util.h | 5 ----- src/tests/mult-s16-test.c
>> | 9 ++------- 2 files changed, 2 insertions(+), 12 deletions(-)
>> 
>> diff --git a/src/pulsecore/sample-util.h
>> b/src/pulsecore/sample-util.h index c817bc9..9862938 100644 ---
>> a/src/pulsecore/sample-util.h +++ b/src/pulsecore/sample-util.h 
>> @@ -55,10 +55,6 @@ void pa_deinterleave(const void *src, void
>> *dst[], unsigned channels, size_t ss, void
>> pa_sample_clamp(pa_sample_format_t format, void *dst, size_t
>> dstr, const void *src, size_t sstr, unsigned n);
>> 
>> static inline int32_t pa_mult_s16_volume(int16_t v, int32_t cv)
>> { -#if __WORDSIZE == 64 || ((ULONG_MAX) > (UINT_MAX)) -    /*
>> Multiply with 64 bit integers on 64 bit platforms */ -    return
>> (v * (int64_t) cv) >> 16; -#else /* Multiplying the 32 bit volume
>> factor with the * 16 bit sample might result in an 48 bit value.
>> We * want to do without 64 bit integers and hence do @@ -68,7
>> +64,6 @@ static inline int32_t pa_mult_s16_volume(int16_t v,
>> int32_t cv) { int32_t hi = cv >> 16; int32_t lo = cv & 0xFFFF; 
>> return ((v * lo) >> 16) + (v * hi); -#endif }
>> 
> 
> Hi! There is probably no portable way for checking CPU type. But
> you do not need to know CPU type here. You need to know if CPU has
> fast 64bit numeric operations (and use 64bit speed optimization),
> right?
> 
> And this could be possible by checking size of int_fast32_t type 
> (defined in stdint.h). If is same as size of int_fast64_t type then
> you could use 64bit optimization otherwise not (= 32bit integers
> are faster then 64bit).
> 
> But I will let this suggestion for reviewing of other people.
> 

This sounds like a good way to go.

I noted that we trigger UB in pa_mult_s16_volume(), as results of bit
shifts over signed integers are undefined. I will try to address it
too (as a separate commit).

>> pa_usec_t pa_bytes_to_usec_round_up(uint64_t length, const
>> pa_sample_spec *spec); diff --git a/src/tests/mult-s16-test.c
>> b/src/tests/mult-s16-test.c index d2a351c..20ad107 100644 ---
>> a/src/tests/mult-s16-test.c +++ b/src/tests/mult-s16-test.c @@
>> -93,13 +93,8 @@ int main(int argc, char *argv[]) { if
>> (!getenv("MAKE_CHECK")) pa_log_set_level(PA_LOG_DEBUG);
>> 
>> -#if __WORDSIZE == 64 || ((ULONG_MAX) > (UINT_MAX)) -
>> pa_log_debug("This seems to be 64-bit code."); -#elif  __WORDSIZE
>> == 32 -    pa_log_debug("This seems to be 32-bit code."); -#else 
>> -    pa_log_debug("Don't know if this is 32- or 64-bit code."); 
>> -#endif +    pa_log_debug("On this platform, integer size is %zu
>> and long size is %zu", +            sizeof(int), sizeof(long));
>> 
>> s = suite_create("Mult-s16"); tc = tcase_create("mult-s16");
> 
> With your change this comment looks now as not useful (but maybe
> I'm mistaken).
> 

I'm going to change the message to: whether there are detected fast
64-bit integer operations.
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