shithub: mp3dec

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Optimize mp3d_scale_pcm using ssat instruction.

--- a/minimp3.h

+++ b/minimp3.h

@@ -191,6 +191,16 @@

 #define HAVE_SIMD 0

 #endif /* !defined(MINIMP3_NO_SIMD) */

+#if defined(__ARM_ARCH) && (__ARM_ARCH >= 6) && !defined(__aarch64__)

+#define HAVE_ARMV6 1

+static __inline__ __attribute__((always_inline)) int32_t minimp3_clip_int16_arm(int32_t a)

+{

+    int32_t x = 0;

+    __asm__ ("ssat %0, #16, %1" : "=r"(x) : "r"(a));

+    return x;

+}

+#endif

+

 typedef struct

 {

     const uint8_t *buf;

@@ -1407,10 +1417,16 @@

 #ifndef MINIMP3_FLOAT_OUTPUT

 static int16_t mp3d_scale_pcm(float sample)

 {

+#if HAVE_ARMV6

+    int32_t s32 = (int32_t)(sample + .5f);

+    s32 -= (s32 < 0);

+    int16_t s = (int16_t)minimp3_clip_int16_arm(s32);

+#else

     if (sample >=  32766.5) return (int16_t) 32767;

     if (sample <= -32767.5) return (int16_t)-32768;

     int16_t s = (int16_t)(sample + .5f);

     s -= (s < 0);   /* away from zero, to be compliant */

+#endif

     return s;

 }

 #else /* MINIMP3_FLOAT_OUTPUT */