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rtl_sdr_fm: make SIMD runtime dispatch thread-safe with pthread_once and ensure AVX2/SSE2 paths compile by relying on function-level target attributes (remove AVX2/SSE2 guards). Gate NEON rotate to AArch64 (ARMv7 falls back to scalar) while retaining NEON widen for portability and performance.

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This commit is contained in:
arancormonk
2025-09-03 23:21:37 -04:00
parent 4e64ef1c11
commit 2ce089ccf8
1 changed files with 14 additions and 16 deletions
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30
src/rtl_sdr_fm.cpp
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@@ -108,6 +108,8 @@ static int upsample_fixedpoint_enabled = 1;/* DSD_FME_UPSAMPLE_FP (1 default) */
/* Forward declaration for runtime SIMD dispatch initializer */
static void dsd_fme_init_runtime_dispatch(void);
static void dsd_fme_init_runtime_dispatch_once(void);
static pthread_once_t dsd_fme_dispatch_once_control = PTHREAD_ONCE_INIT;
/* =====================
USB widening helper dispatch setup
@@ -191,7 +193,6 @@ static inline void widen_rotate90_u8_to_s16_bias127_scalar(const unsigned char *
/* AVX2 specializations */
static void DSD_FME_TARGET_ATTR("avx2") widen_u8_to_s16_bias127_avx2(const unsigned char *src, int16_t *dst, uint32_t len)
{
#if defined(__AVX2__)
uint32_t i = 0;
const __m256i bias256 = _mm256_set1_epi16(127);
for (; i + 32 <= len; i += 32) {
@@ -205,14 +206,10 @@ static void DSD_FME_TARGET_ATTR("avx2") widen_u8_to_s16_bias127_avx2(const unsig
_mm256_storeu_si256((__m256i*)(dst + i + 16), hi);
}
for (; i < len; i++) dst[i] = (int16_t)src[i] - 127;
#else
widen_u8_to_s16_bias127_scalar(src, dst, len);
#endif
}
static void DSD_FME_TARGET_ATTR("avx2") widen_rotate90_u8_to_s16_bias127_avx2(const unsigned char *src, int16_t *dst, uint32_t len)
{
#if defined(__AVX2__)
const __m256i shuffle = _mm256_setr_epi8(
0, 1, 3, 2, 4, 5, 7, 6, 8, 9,11,10,12,13,15,14,
0, 1, 3, 2, 4, 5, 7, 6, 8, 9,11,10,12,13,15,14);
@@ -242,15 +239,11 @@ static void DSD_FME_TARGET_ATTR("avx2") widen_rotate90_u8_to_s16_bias127_avx2(co
dst[i + 0] = (int16_t)src[i + 0] - 127;
dst[i + 1] = (int16_t)src[i + 1] - 127;
}
#else
widen_rotate90_u8_to_s16_bias127_scalar(src, dst, len);
#endif
}
/* SSE2 specializations (safe on x86_64; guarded by runtime dispatch) */
static void DSD_FME_TARGET_ATTR("sse2") widen_u8_to_s16_bias127_sse2(const unsigned char *src, int16_t *dst, uint32_t len)
{
#if defined(__SSE2__)
uint32_t i = 0;
const __m128i bias = _mm_set1_epi16(127);
const __m128i zero = _mm_setzero_si128();
@@ -264,9 +257,6 @@ static void DSD_FME_TARGET_ATTR("sse2") widen_u8_to_s16_bias127_sse2(const unsig
_mm_storeu_si128((__m128i*)(dst + i + 8), hi);
}
for (; i < len; i++) dst[i] = (int16_t)src[i] - 127;
#else
widen_u8_to_s16_bias127_scalar(src, dst, len);
#endif
}
static void DSD_FME_TARGET_ATTR("sse2") widen_rotate90_u8_to_s16_bias127_sse2(const unsigned char *src, int16_t *dst, uint32_t len)
@@ -296,6 +286,7 @@ static void widen_u8_to_s16_bias127_neon(const unsigned char *src, int16_t *dst,
static void widen_rotate90_u8_to_s16_bias127_neon(const unsigned char *src, int16_t *dst, uint32_t len)
{
#if defined(__aarch64__)
const uint8x16_t tbl_idx = {0,1,3,2,4,5,7,6, 8,9,11,10,12,13,15,14};
const int16x8_t c127 = vdupq_n_s16(127);
const int16x8_t c128 = vdupq_n_s16(128);
@@ -322,15 +313,16 @@ static void widen_rotate90_u8_to_s16_bias127_neon(const unsigned char *src, int1
dst[i + 0] = (int16_t)src[i + 0] - 127;
dst[i + 1] = (int16_t)src[i + 1] - 127;
}
#else
/* ARMv7 NEON lacks vqtbl1q_u8; use scalar fallback for rotate+widen */
widen_rotate90_u8_to_s16_bias127_scalar(src, dst, len);
#endif
}
#endif
/* Non-privileged CPU feature checks (CPUID/XGETBV on x86, getauxval on Linux/ARM) */
static void dsd_fme_init_runtime_dispatch(void)
static void dsd_fme_init_runtime_dispatch_once(void)
{
static int done = 0;
if (done) return;
done = 1;
int use_avx2 = 0;
int use_sse2 = 0;
@@ -399,6 +391,12 @@ static void dsd_fme_init_runtime_dispatch(void)
#endif
}
static void dsd_fme_init_runtime_dispatch(void)
{
/* Thread-safe, idempotent initialization */
pthread_once(&dsd_fme_dispatch_once_control, dsd_fme_init_runtime_dispatch_once);
}
/* =====================
Saturating helpers
===================== */