[Bug target/112447] risc-v regression: FAIL: gcc.c-torture/execute/memset-3.c -O3

[juzhe.zhong at rivai dot ai via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112447

--- Comment #14 from JuzheZhong <juzhe.zhong at rivai dot ai> ---
Let me give you some guide which helps you to dig into the problem.

First, reduce the case as follows:

#include <string.h>

void abort (void);
void exit (int);

#ifndef MAX_OFFSET
#define MAX_OFFSET (sizeof (long long))
#endif

#ifndef MAX_COPY
#define MAX_COPY 15
#endif

#ifndef MAX_EXTRA
#define MAX_EXTRA (sizeof (long long))
#endif

#define MAX_LENGTH (MAX_OFFSET + MAX_COPY + MAX_EXTRA)

static union {
  char buf[MAX_LENGTH];
  long long align_int;
  long double align_fp;
} u;

char A = 'A';

void reset ()
{
  int i;

  for (i = 0; i < MAX_LENGTH; i++)
    u.buf[i] = 'a';
}

void check (int off, int len, int ch)
{
  char *q;
  int i;

  q = u.buf;
  for (i = 0; i < off; i++, q++)
    if (*q != 'a')
      abort ();

  for (i = 0; i < len; i++, q++)
    if (*q != ch)
      abort ();

  for (i = 0; i < MAX_EXTRA; i++, q++)
    if (*q != 'a')
      abort ();
}

int main ()
{
  int len;
  char *p;

  /* off == 0 */
  for (len = 0; len < MAX_COPY; len++)
    {
      reset ();

      p = memset (u.buf, '\0', len);
      if (p != u.buf) abort ();
      check (0, len, '\0');

      p = memset (u.buf, A, len);
      if (p != u.buf) abort ();
      check (0, len, 'A');

      p = memset (u.buf, 'B', len);
      if (p != u.buf) abort ();
      check (0, len, 'B');
    }

  /* off == 1 */
  for (len = 0; len < MAX_COPY; len++)
    {
      reset ();

      p = memset (u.buf+1, '\0', len);
      if (p != u.buf+1) abort ();
      check (1, len, '\0');

      p = memset (u.buf+1, A, len);
      if (p != u.buf+1) abort ();
      check (1, len, 'A');

      p = memset (u.buf+1, 'B', len);
      if (p != u.buf+1) abort ();
      check (1, len, 'B');
    }

  exit (0);
}