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audio: Fix ARM NEON audio converter bugs.
(Patch from Sylvain, I'm just applying it.)

Fixes Bugzilla #4186.
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icculus committed Jun 14, 2019
1 parent 5c56c88 commit 33b235f4c3dcac56fdc9f05b02289e4396df9c6e
Showing 1 changed file with 9 additions and 10 deletions.
@@ -25,8 +25,7 @@
#include "SDL_cpuinfo.h"
#include "SDL_assert.h"

/* !!! FIXME: disabled until we fix https://bugzilla.libsdl.org/show_bug.cgi?id=4186 */
#if 0 /*def __ARM_NEON */
#ifdef __ARM_NEON
#define HAVE_NEON_INTRINSICS 1
#endif

@@ -926,16 +925,16 @@ SDL_Convert_U8_to_F32_NEON(SDL_AudioCVT *cvt, SDL_AudioFormat format)
/* Aligned! Do NEON blocks as long as we have 16 bytes available. */
const uint8_t *mmsrc = (const uint8_t *) src;
const float32x4_t divby128 = vdupq_n_f32(DIVBY128);
const float32x4_t one = vdupq_n_f32(1.0f);
const float32x4_t negone = vdupq_n_f32(-1.0f);
while (i >= 16) { /* 16 * 8-bit */
const uint8x16_t bytes = vld1q_u8(mmsrc); /* get 16 uint8 into a NEON register. */
const uint16x8_t uint16hi = vmovl_u8(vget_high_u8(bytes)); /* convert top 8 bytes to 8 uint16 */
const uint16x8_t uint16lo = vmovl_u8(vget_low_u8(bytes)); /* convert bottom 8 bytes to 8 uint16 */
/* split uint16 to two uint32, then convert to float, then multiply to normalize, subtract to adjust for sign, store. */
vst1q_f32(dst, vmlsq_f32(vcvtq_f32_u32(vmovl_u16(vget_high_u16(uint16hi))), divby128, one));
vst1q_f32(dst+4, vmlsq_f32(vcvtq_f32_u32(vmovl_u16(vget_low_u16(uint16hi))), divby128, one));
vst1q_f32(dst+8, vmlsq_f32(vcvtq_f32_u32(vmovl_u16(vget_high_u16(uint16lo))), divby128, one));
vst1q_f32(dst+12, vmlsq_f32(vcvtq_f32_u32(vmovl_u16(vget_low_u16(uint16lo))), divby128, one));
vst1q_f32(dst, vmlaq_f32(negone, vcvtq_f32_u32(vmovl_u16(vget_high_u16(uint16hi))), divby128));
vst1q_f32(dst+4, vmlaq_f32(negone, vcvtq_f32_u32(vmovl_u16(vget_low_u16(uint16hi))), divby128));
vst1q_f32(dst+8, vmlaq_f32(negone, vcvtq_f32_u32(vmovl_u16(vget_high_u16(uint16lo))), divby128));
vst1q_f32(dst+12, vmlaq_f32(negone, vcvtq_f32_u32(vmovl_u16(vget_low_u16(uint16lo))), divby128));
i -= 16; mmsrc -= 16; dst -= 16;
}

@@ -1021,12 +1020,12 @@ SDL_Convert_U16_to_F32_NEON(SDL_AudioCVT *cvt, SDL_AudioFormat format)
if ((((size_t) src) & 15) == 0) {
/* Aligned! Do NEON blocks as long as we have 16 bytes available. */
const float32x4_t divby32768 = vdupq_n_f32(DIVBY32768);
const float32x4_t one = vdupq_n_f32(1.0f);
const float32x4_t negone = vdupq_n_f32(-1.0f);
while (i >= 8) { /* 8 * 16-bit */
const uint16x8_t uints = vld1q_u16((uint16_t const *) src); /* get 8 uint16 into a NEON register. */
/* split uint16 to two int32, then convert to float, then multiply to normalize, subtract for sign, store. */
vst1q_f32(dst, vmlsq_f32(one, vcvtq_f32_u32(vmovl_u16(vget_low_u16(uints))), divby32768));
vst1q_f32(dst+4, vmlsq_f32(one, vcvtq_f32_u32(vmovl_u16(vget_high_u16(uints))), divby32768));
vst1q_f32(dst, vmlaq_f32(negone, vcvtq_f32_u32(vmovl_u16(vget_low_u16(uints))), divby32768));
vst1q_f32(dst+4, vmlaq_f32(negone, vcvtq_f32_u32(vmovl_u16(vget_high_u16(uints))), divby32768));
i -= 8; src -= 8; dst -= 8;
}
}

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