__lsx_vssrarni_wu_d

LSX intrinsic · group: Shift

Synopsis

__m128i __lsx_vssrarni_wu_d (__m128i a, __m128i b, imm0_63 imm)
#include <lsxintrin.h>
Instruction: vssrarni.wu.d vr, vr, imm
CPU Flags: LSX

Description

Arithmetic right shift with rounding the signed 64-bit elements in a and b by imm, saturate the result to unsigned 32-bit, write the 32-bit result into the lower half of each 128-bit lane of dst, and zero the upper half.

Operation

for (int i = 0; i < 4; i++) {
  if (i < 2) {
    s64 temp;
    if (imm == 0) {
      temp = (s64)b.dword[i];
    } else {
      temp = ((s64)b.dword[i] >> imm) + (((s64)b.dword[i] >> (imm - 1)) & 1);
    }
    dst.word[i] = clamp<s64>(temp, 0, 4294967295);
  } else {
    s64 temp;
    if (imm == 0) {
      temp = (s64)a.dword[i - 2];
    } else {
      temp = ((s64)a.dword[i - 2] >> imm) +
             (((s64)a.dword[i - 2] >> (imm - 1)) & 1);
    }
    dst.word[i] = clamp<s64>(temp, 0, 4294967295);
  }
}

Tested on real machine.

Latency and Throughput

CPU	µarch	Latency	Throughput (IPC)
3C5000	LA464	4	1
3A6000	LA664	4	2
3C6000	LA664	4	2
2K1000LA	LA264	3	0.5(1/2)
2K3000	LA364E	3	0.5(1/2)

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