__lsx_vhaddw_w_h

LSX intrinsic · group: Integer Computation

Synopsis

__m128i __lsx_vhaddw_w_h (__m128i a, __m128i b)
#include <lsxintrin.h>
Instruction: vhaddw.w.h vr, vr, vr
CPU Flags: LSX

Description

Add odd-positioned signed 16-bit elements in a to even-positioned signed 16-bit elements in b, sign-extending both to 32-bit, to get the 32-bit result.

Operation

for (int i = 0; i < 4; i++) {
  dst.word[i] = (s32)(s16)a.half[2 * i + 1] + (s32)(s16)b.half[2 * i];
}

// Expands to:

if (0) {
  dst.word[0] = ((s32)((s16)a.half[1])) + ((s32)((s16)b.half[0]));
  dst.word[1] = ((s32)((s16)a.half[3])) + ((s32)((s16)b.half[2]));
  dst.word[2] = ((s32)((s16)a.half[5])) + ((s32)((s16)b.half[4]));
  dst.word[3] = ((s32)((s16)a.half[7])) + ((s32)((s16)b.half[6]));
}

Tested on real machine.

Latency and Throughput

CPU	µarch	Latency	Throughput (IPC)
3C5000	LA464	2	2
3A6000	LA664	2	2
3C6000	LA664	2	2
2K1000LA	LA264	2	1
2K3000	LA364E	2	1

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