[Bug target/67765] New: [SH] Improve treg_combine pass

[olegendo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67765

            Bug ID: 67765
           Summary: [SH] Improve treg_combine pass
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: olegendo at gcc dot gnu.org
  Target Milestone: ---
            Target: sh*-*-*

Currently the sh_treg_combine.cc pass uses conditional branches as a trigger
for its optimizations.  However, if the addsicc pattern is added from PR 54236
attachment 36012, then the following reduced test case, compiled with -O2 -m4
-ml, will exhibit the following sequence:

        cmp/eq  #32,r0
        movt    r7
.L7:
        cmp/hi  r6,r2
        bf/s    .L8
        tst     r7,r7     << r7 known to be 0 or 1 because of preceeding movt
        mov     #-1,r1
        addc    r1,r2     << r7 == 0: r2 = r2 + (-1) + 1 = r2 + 0
                             r7 == 1: r2 = r2 + (-1) + 0 = r2 - 1
                             r2 = r2 - r1

Without the addsicc pattern, a "sub r1,r2" is generated.  The treg_combine pass
should actually be triggered by the tst insn and should propagate known reg
values that originated from a movt or movrt insn into the following insns.


extern void free_bootmem (unsigned long addr, unsigned long size);

struct { unsigned long addr, size, type; } memory_chunk[16] = { { 0 } };

static char command_line[896] = { 0, };

void setup_arch(char **cmdline_p)
{
  char c = ' ', cn, *to = command_line, *from = ((char *) (0x10480));
  unsigned long start_pfn, end_pfn;
  int i = 0;

  for (;;)
  {
    cn = *(from++);
    if (!cn)
      break;
    if (cn == ' ' && c == ' ')
      continue;
    c = cn;
    if (to - command_line >= 896)
      break;
    *(to++) = c;
  }

  if (c == ' ' && to > command_line)
    to--;

  *to = '\0';

  unsigned long start_chunk, end_chunk;

  start_chunk = (memory_chunk[i].addr + (1UL << 12) - 1);
  start_chunk >>= 12;
  end_chunk = (memory_chunk[i].addr + memory_chunk[i].size);

  end_chunk >>= 12;
  if (start_chunk < start_pfn)
    start_chunk = start_pfn;
  if (end_chunk > end_pfn)
    end_chunk = end_pfn;
  if (start_chunk < end_chunk)
    free_bootmem(start_chunk << 12, (end_chunk - start_chunk) << 12);
}