[PATCH 2/2] endianmacros: Replace borked PA_FLOAT32_SWAP() with PA_READ_FLOAT32RE() / PA_WRITE_FLOAT32RE()

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I was considering whether "const void *p"  should instead be a "const 
float *p" (in the function prototypes), but maybe not - a reversed float 
cannot be considered a float anymore, due to the NaN problems you 
describe below.

OTOH, that leaves us with a few float pointers in the callers to these 
functions, which should perhaps be converted to void* too, but then you 
can't index them...

So hey, it fixes a bug, and I assume you have run the relevant tests and 
they succeeded. So while it's slightly inconsistent to mix float* and 
void*, this one is acked too.

On 2014-09-03 02:25, Peter Meerwald wrote:
> From: Peter Meerwald <pmeerw at debian>
>
> building PA with -O0 leads to test failure in mix-test on i386
>
> issue reported by Felipe, see
> http://lists.freedesktop.org/archives/pulseaudio-discuss/2014-August/021406.html
>
> the problem is the value 0xbeffbd7f: when byte-swapped it becomes 0x7fbdffbe and according
> to IEEE-754 represents a signalling NaN (starting with s111 1111 10, see http://en.wikipedia.org/wiki/NaN)
>
> when this value is assigned to a floating point register, it becomes 0x7ffdffbe, representing
> a quiet NaN (starting with s111 1111 11) -- a signalling NaN is turned into a quiet NaN!
>
> so PA_FLOAT32_SWAP(PA_FLOAT32_SWAP(x)) != x for certain values, uhuh!
>
> the following test code can be used; due to volatile, it will always demonstrate the issue;
> without volatile, it depends on the optimization level (i386, 32-bit, gcc 4.9):
>
> // snip
>
> static inline float PA_FLOAT32_SWAP(float x) {
>      union {
>          float f;
>          uint32_t u;
>      } t;
>
>      t.f = x;
>      t.u = bswap_32(t.u);
>      return t.f;
> }
>
> int main() {
>    unsigned x = 0xbeffbd7f;
>    volatile float f = PA_FLOAT32_SWAP(*(float *)&x);
>    printf("%08x %08x %08x %f\n", 0xbeffbd7f, *(unsigned *)&f, bswap_32(*(unsigned *)&f), f);
> }
> // snip
>
> the problem goes away with optimization when no temporary floating point registers are used
>
> the proposed solution is to avoid passing swapped floating point data in a
> float; this is done with new functions PA_READ_FLOAT32RE() and PA_WRITE_FLOAT32RE()
> which use uint32_t to dereference a pointer and byte-swap the data, hence no temporary
> float variable is used
>
> also delete PA_FLOAT32_TO_LE()/_BE(), not used
>
> Signed-off-by: Peter Meerwald <pmeerw at pmeerw.net>
> Reported-by: Felipe Sateler <fsateler at debian.org>
> ---
>   src/pulsecore/endianmacros.h | 23 ++++++++++++-----------
>   src/pulsecore/mix.c          | 11 ++++-------
>   src/pulsecore/sample-util.c  |  4 ++--
>   src/pulsecore/sconv-s16le.c  | 22 ++++++++--------------
>   src/pulsecore/svolume_c.c    |  4 ++--
>   src/tests/mix-test.c         |  4 ++--
>   src/tests/resampler-test.c   |  4 ++--
>   7 files changed, 32 insertions(+), 40 deletions(-)
>
> diff --git a/src/pulsecore/endianmacros.h b/src/pulsecore/endianmacros.h
> index 4822fc4..2e73136 100644
> --- a/src/pulsecore/endianmacros.h
> +++ b/src/pulsecore/endianmacros.h
> @@ -71,25 +71,32 @@ static inline void PA_WRITE24LE(uint8_t *p, uint32_t u) {
>       p[0] = (uint8_t) u;
>   }
>
> -static inline float PA_FLOAT32_SWAP(float x) {
> +static inline float PA_READ_FLOAT32RE(const void *p) {
>       union {
>           float f;
>           uint32_t u;
>       } t;
>
> -    t.f = x;
> -    t.u = PA_UINT32_SWAP(t.u);
> +    t.u = PA_UINT32_SWAP(*(uint32_t *) p);
>       return t.f;
>   }
>
> +static inline void PA_WRITE_FLOAT32RE(void *p, float x) {
> +    union {
> +        float f;
> +        uint32_t u;
> +    } t;
> +
> +    t.f = x;
> +    *(uint32_t *) p = PA_UINT32_SWAP(t.u);
> +}
> +
>   #define PA_MAYBE_INT16_SWAP(c,x) ((c) ? PA_INT16_SWAP(x) : (x))
>   #define PA_MAYBE_UINT16_SWAP(c,x) ((c) ? PA_UINT16_SWAP(x) : (x))
>
>   #define PA_MAYBE_INT32_SWAP(c,x) ((c) ? PA_INT32_SWAP(x) : (x))
>   #define PA_MAYBE_UINT32_SWAP(c,x) ((c) ? PA_UINT32_SWAP(x) : (x))
>
> -#define PA_MAYBE_FLOAT32_SWAP(c,x) ((c) ? PA_FLOAT32_SWAP(x) : (x))
> -
>   #ifdef WORDS_BIGENDIAN
>    #define PA_INT16_FROM_LE(x) PA_INT16_SWAP(x)
>    #define PA_INT16_FROM_BE(x) ((int16_t)(x))
> @@ -115,9 +122,6 @@ static inline float PA_FLOAT32_SWAP(float x) {
>    #define PA_UINT32_TO_LE(x) PA_UINT32_SWAP(x)
>    #define PA_UINT32_TO_BE(x) ((uint32_t)(x))
>
> - #define PA_FLOAT32_TO_LE(x) PA_FLOAT32_SWAP(x)
> - #define PA_FLOAT32_TO_BE(x) ((float) (x))
> -
>    #define PA_READ24NE(x) PA_READ24BE(x)
>    #define PA_WRITE24NE(x,y) PA_WRITE24BE((x),(y))
>
> @@ -148,9 +152,6 @@ static inline float PA_FLOAT32_SWAP(float x) {
>    #define PA_UINT32_TO_LE(x) ((uint32_t)(x))
>    #define PA_UINT32_TO_BE(x) PA_UINT32_SWAP(x)
>
> - #define PA_FLOAT32_TO_LE(x) ((float) (x))
> - #define PA_FLOAT32_TO_BE(x) PA_FLOAT32_SWAP(x)
> -
>    #define PA_READ24NE(x) PA_READ24LE(x)
>    #define PA_WRITE24NE(x,y) PA_WRITE24LE((x),(y))
>
> diff --git a/src/pulsecore/mix.c b/src/pulsecore/mix.c
> index 10567d6..03c71f0 100644
> --- a/src/pulsecore/mix.c
> +++ b/src/pulsecore/mix.c
> @@ -576,17 +576,14 @@ static void pa_mix_float32re_c(pa_mix_info streams[], unsigned nstreams, unsigne
>
>           for (i = 0; i < nstreams; i++) {
>               pa_mix_info *m = streams + i;
> -            float v, cv = m->linear[channel].f;
> +            float cv = m->linear[channel].f;
>
> -            if (PA_LIKELY(cv > 0)) {
> -                v = PA_FLOAT32_SWAP(*(float*) m->ptr);
> -                v *= cv;
> -                sum += v;
> -            }
> +            if (PA_LIKELY(cv > 0))
> +                sum += PA_READ_FLOAT32RE(m->ptr) * cv;
>               m->ptr = (uint8_t*) m->ptr + sizeof(float);
>           }
>
> -        *data = PA_FLOAT32_SWAP(sum);
> +        PA_WRITE_FLOAT32RE(data, sum);
>
>           if (PA_UNLIKELY(++channel >= channels))
>               channel = 0;
> diff --git a/src/pulsecore/sample-util.c b/src/pulsecore/sample-util.c
> index dc5c1fd..539f3b8 100644
> --- a/src/pulsecore/sample-util.c
> +++ b/src/pulsecore/sample-util.c
> @@ -296,9 +296,9 @@ void pa_sample_clamp(pa_sample_format_t format, void *dst, size_t dstr, const vo
>           for (; n > 0; n--) {
>               float f;
>
> -            f = PA_FLOAT32_SWAP(*s);
> +            f = PA_READ_FLOAT32RE(s);
>               f = PA_CLAMP_UNLIKELY(f, -1.0f, 1.0f);
> -            *d = PA_FLOAT32_SWAP(f);
> +            PA_WRITE_FLOAT32RE(d, f);
>
>               s = (const float*) ((const uint8_t*) s + sstr);
>               d = (float*) ((uint8_t*) d + dstr);
> diff --git a/src/pulsecore/sconv-s16le.c b/src/pulsecore/sconv-s16le.c
> index 45cf972..0c1d16c 100644
> --- a/src/pulsecore/sconv-s16le.c
> +++ b/src/pulsecore/sconv-s16le.c
> @@ -157,8 +157,7 @@ void pa_sconv_s16le_to_float32re(unsigned n, const int16_t *a, float *b) {
>       for (; n > 0; n--) {
>           int16_t s = *(a++);
>           float k = INT16_FROM(s) * (1.0f / (1 << 15));
> -        k = PA_FLOAT32_SWAP(k);
> -        *(b++) = k;
> +        PA_WRITE_FLOAT32RE(b++, k);
>       }
>   }
>
> @@ -169,8 +168,7 @@ void pa_sconv_s32le_to_float32re(unsigned n, const int32_t *a, float *b) {
>       for (; n > 0; n--) {
>           int32_t s = *(a++);
>           float k = INT32_FROM(s) * (1.0f / (1U << 31));
> -        k = PA_FLOAT32_SWAP(k);
> -        *(b++) = k;
> +        PA_WRITE_FLOAT32RE(b++, k);
>       }
>   }
>
> @@ -180,8 +178,7 @@ void pa_sconv_s16le_from_float32re(unsigned n, const float *a, int16_t *b) {
>
>       for (; n > 0; n--) {
>           int16_t s;
> -        float v = *(a++);
> -        v = PA_FLOAT32_SWAP(v) * (1 << 15);
> +        float v = PA_READ_FLOAT32RE(a++) * (1 << 15);
>           s = (int16_t) PA_CLAMP_UNLIKELY(lrintf(v), -0x8000, 0x7FFF);
>           *(b++) = INT16_TO(s);
>       }
> @@ -193,8 +190,7 @@ void pa_sconv_s32le_from_float32re(unsigned n, const float *a, int32_t *b) {
>
>       for (; n > 0; n--) {
>           int32_t s;
> -        float v = *(a++);
> -        v = PA_FLOAT32_SWAP(v) * (1U << 31);
> +        float v = PA_READ_FLOAT32RE(a++) * (1U << 31);
>           s = (int32_t) PA_CLAMP_UNLIKELY(llrintf(v), -0x80000000LL, 0x7FFFFFFFLL);
>           *(b++) = INT32_TO(s);
>       }
> @@ -325,7 +321,7 @@ void pa_sconv_s24le_to_float32re(unsigned n, const uint8_t *a, float *b) {
>       for (; n > 0; n--) {
>           int32_t s = READ24(a) << 8;
>           float k = s * (1.0f / (1U << 31));
> -        *b = PA_FLOAT32_SWAP(k);
> +        PA_WRITE_FLOAT32RE(b, k);
>           a += 3;
>           b++;
>       }
> @@ -337,8 +333,7 @@ void pa_sconv_s24le_from_float32re(unsigned n, const float *a, uint8_t *b) {
>
>       for (; n > 0; n--) {
>           int32_t s;
> -        float v = *a;
> -        v = PA_FLOAT32_SWAP(v) * (1U << 31);
> +        float v = PA_READ_FLOAT32RE(a) * (1U << 31);
>           s = (int32_t) PA_CLAMP_UNLIKELY(llrint(v), -0x80000000LL, 0x7FFFFFFFLL);
>           WRITE24(b, ((uint32_t) s) >> 8);
>           a++;
> @@ -411,7 +406,7 @@ void pa_sconv_s24_32le_to_float32re(unsigned n, const uint32_t *a, float *b) {
>       for (; n > 0; n--) {
>           int32_t s = (int32_t) (UINT32_FROM(*a) << 8);
>           float k = s * (1.0f / (1U << 31));
> -        *b = PA_FLOAT32_SWAP(k);
> +        PA_WRITE_FLOAT32RE(b, k);
>           a++;
>           b++;
>       }
> @@ -437,8 +432,7 @@ void pa_sconv_s24_32le_from_float32re(unsigned n, const float *a, uint32_t *b) {
>
>       for (; n > 0; n--) {
>           int32_t s;
> -        float v = *a;
> -        v = PA_FLOAT32_SWAP(v) * (1U << 31);
> +        float v = PA_READ_FLOAT32RE(a) * (1U << 31);
>           s = (int32_t) PA_CLAMP_UNLIKELY(llrint(v), -0x80000000LL, 0x7FFFFFFFLL);
>           *b = UINT32_TO(((uint32_t) s) >> 8);
>           a++;
> diff --git a/src/pulsecore/svolume_c.c b/src/pulsecore/svolume_c.c
> index ad2df18..2e2db12 100644
> --- a/src/pulsecore/svolume_c.c
> +++ b/src/pulsecore/svolume_c.c
> @@ -125,9 +125,9 @@ static void pa_volume_float32re_c(float *samples, const float *volumes, unsigned
>       for (channel = 0; length; length--) {
>           float t;
>
> -        t = PA_FLOAT32_SWAP(*samples);
> +        t = PA_READ_FLOAT32RE(samples);
>           t *= volumes[channel];
> -        *samples++ = PA_FLOAT32_SWAP(t);
> +        PA_WRITE_FLOAT32RE(samples++, t);
>
>           if (PA_UNLIKELY(++channel >= channels))
>               channel = 0;
> diff --git a/src/tests/mix-test.c b/src/tests/mix-test.c
> index d5bae13..e95607d 100644
> --- a/src/tests/mix-test.c
> +++ b/src/tests/mix-test.c
> @@ -150,7 +150,7 @@ static void compare_block(const pa_sample_spec *ss, const pa_memchunk *chunk, in
>               float *u = d;
>
>               for (i = 0; i < chunk->length / pa_frame_size(ss); i++) {
> -                float uu = PA_MAYBE_FLOAT32_SWAP(ss->format != PA_SAMPLE_FLOAT32NE, *u);
> +                float uu = ss->format == PA_SAMPLE_FLOAT32NE ? *u : PA_READ_FLOAT32RE(u);
>                   fail_unless(fabsf(uu - *v) <= 1e-6f, NULL);
>                   ++u;
>                   ++v;
> @@ -264,7 +264,7 @@ static pa_memblock* generate_block(pa_mempool *pool, const pa_sample_spec *ss) {
>               if (ss->format == PA_SAMPLE_FLOAT32RE) {
>                   float *u = d;
>                   for (i = 0; i < 10; i++)
> -                    u[i] = PA_FLOAT32_SWAP(float32ne_result[0][i]);
> +                    PA_WRITE_FLOAT32RE(&u[i], float32ne_result[0][i]);
>               } else
>                   memcpy(d, float32ne_result[0], sizeof(float32ne_result[0]));
>
> diff --git a/src/tests/resampler-test.c b/src/tests/resampler-test.c
> index 60345af..f547770 100644
> --- a/src/tests/resampler-test.c
> +++ b/src/tests/resampler-test.c
> @@ -98,7 +98,7 @@ static void dump_block(const char *label, const pa_sample_spec *ss, const pa_mem
>               float *u = d;
>
>               for (i = 0; i < chunk->length / pa_frame_size(ss); i++) {
> -                printf("%4.3g ", ss->format == PA_SAMPLE_FLOAT32NE ? *u : PA_FLOAT32_SWAP(*u));
> +                printf("%4.3g ", ss->format == PA_SAMPLE_FLOAT32NE ? *u : PA_READ_FLOAT32RE(u));
>                   u++;
>               }
>
> @@ -222,7 +222,7 @@ static pa_memblock* generate_block(pa_mempool *pool, const pa_sample_spec *ss) {
>
>               if (ss->format == PA_SAMPLE_FLOAT32RE)
>                   for (i = 0; i < 10; i++)
> -                    u[i] = PA_FLOAT32_SWAP(u[i]);
> +                    PA_WRITE_FLOAT32RE(&u[i], u[i]);
>
>               break;
>           }
>

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic


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