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Optimized and correct version of movemask128 for ARM #102

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Apr 18, 2022
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Optimized and correct version of movemask128 for ARM #102

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20 changes: 9 additions & 11 deletions src/util/arch/arm/simd_utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -379,17 +379,15 @@ static really_inline m128 eq64_m128(m128 a, m128 b) {
}

static really_inline u32 movemask128(m128 a) {
static const uint8x16_t powers = { 1, 2, 4, 8, 16, 32, 64, 128, 1, 2, 4, 8, 16, 32, 64, 128 };

// Compute the mask from the input
uint8x16_t mask = (uint8x16_t) vpaddlq_u32(vpaddlq_u16(vpaddlq_u8(vandq_u8((uint8x16_t)a, powers))));
uint8x16_t mask1 = vextq_u8(mask, (uint8x16_t)zeroes128(), 7);
mask = vorrq_u8(mask, mask1);

// Get the resulting bytes
uint16_t output;
vst1q_lane_u16((uint16_t*)&output, (uint16x8_t)mask, 0);
return output;
uint8x16_t input = vreinterpretq_u8_s32(a);
uint16x8_t high_bits = vreinterpretq_u16_u8(vshrq_n_u8(input, 7));
uint32x4_t paired16 =
vreinterpretq_u32_u16(vsraq_n_u16(high_bits, high_bits, 7));
uint64x2_t paired32 =
vreinterpretq_u64_u32(vsraq_n_u32(paired16, paired16, 14));
uint8x16_t paired64 =
vreinterpretq_u8_u64(vsraq_n_u64(paired32, paired32, 28));
return vgetq_lane_u8(paired64, 0) | ((int) vgetq_lane_u8(paired64, 8) << 8);
}

static really_inline m128 set1_16x8(u8 c) {
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