[Bug rtl-optimization/109866] New: Sometimes using sub/test instead just test

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109866

            Bug ID: 109866
           Summary: Sometimes using sub/test instead just test
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int g(void); int h(void); int t(void);
int f(int a, int b)
{
  int c = a - b;
  if(c == 0)
    return g();
  if (c > 0)
    return h();
  return t();
}
```
This is reduced from bzip2 in spec 2006, though I am not so sure any more.
On x86_64 GCC produces:
```
        subl    %esi, %edi
        testl   %edi, %edi
        je      .L5
        jle     .L3
        jmp     h()
.L3:
        jmp     t()
.L5:
        jmp     g()
```
But GCC should produce (likes clang/LLVM does):
```
        cmpl    %esi, %edi
        je      .L5
        jle     .L3
        jmp     h()
.L3:
        jmp     t()
.L5:
        jmp     g()
```

Note a similar thing happens with aarch64 target too.