__lsx_vfrstp_b

LSX intrinsic · group: Misc

Synopsis

__m128i __lsx_vfrstp_b (__m128i a, __m128i b, __m128i c)
#include <lsxintrin.h>
Instruction: vfrstp.b vr, vr, vr
CPU Flags: LSX

Description

For each 128-bit lane, find the first negative 8-bit element in b. Write its index into the lane of a selected by the first element of the corresponding lane of c modulo 16, or write the maximum valid index plus one if no such element exists. Other elements of a remain unchanged.

Operation

for (int i = 0; i < 16; i++) {
  dst.byte[i] = a.byte[i];
}
int i;
for (i = 0; i < 16; i++) {
  if ((s8)b.byte[i] < 0) {
    break;
  }
}
dst.byte[c.byte[0] % 16] = i;

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	1	1

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