[Bug] Instruction rv64uv-vaadd result of Ara is different from result of Spike.

[jin8495]

I added a test case into vaadd intending to happen overflow as below.

// rv64uv/vaadd.c

#include "vector_macros.h"

void TEST_CASE1(void) {
// ...
}

void TEST_CASE2(void) {
// ...
}

void TEST_CASE3(void) {
// ...
}

// Dont use VCLEAR here, it results in a glitch where are values are off by 1
void TEST_CASE4(void) {
// ...
}

void TEST_CASE5(void) {
  set_vxrm(0); // setting vxrm to rnu rounding mode
  VSET(4, e8, m1);
  VLOAD_8(v1, -128, -128, -128, 128);
  VLOAD_8(v2, -2, -2, -2, -2);
  __asm__ volatile("vaadd.vv v3, v1, v2" ::);
  VCMP_U8(5, v3, -65, -65, -65, -65);
}

int main(void) {
  INIT_CHECK();
  enable_vec();
  TEST_CASE1();
  TEST_CASE2();
  TEST_CASE3();
  TEST_CASE4();
  TEST_CASE5();
  EXIT_CHECK();
}

And when I launched Spike to check the result. It passed the test.

But Verilator answers the test differently.

[mp-17]

Hello @jin8495,

Thanks a lot for pointing that out! @M-Ijaz-10x, we can use this example to debug the issue :-)