[Bug rtl-optimization/58517] icvt (after combine) puts ccreg clobbering insn between ccset insn and cc use

[olegendo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58517

Oleg Endo <olegendo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-10-05
          Component|target                      |rtl-optimization
            Summary|[SH] wrong code with subc   |icvt (after combine) puts
                   |and movsicc                 |ccreg clobbering insn
                   |(-mpretend-cmove) after ce2 |between ccset insn and cc
                   |                            |use
     Ever confirmed|0                           |1

--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> ---
This seems to be a bug in ifcvt.c

Reduced test cases:

int
test_subc (int q, int read, int end)
{
  return q < read ? (read - q - 1) : (end - q);
}

int
test_addc (int q, int read, int end)
{
  return q < read ? (read + q + 1) : (end + q);
}

compiled with -O2 -m4 -mpretend-cmove:

_test_subc:
        sett
        mov     r5,r0
        sub     r4,r6
        subc    r4,r0   ! 36    *subc
        bf      0f      ! 34    *movsicc_t_true/1
        mov     r6,r0
0:
        rts    
        nop

_test_addc:
        sett
        mov     r4,r0
        add     r4,r6
        addc    r5,r0   ! 34    *addc
        bf      0f      ! 32    *movsicc_t_true/1
        mov     r6,r0
0:
        rts    
        nop

In both above cases the comparison 'q < read' is eliminated, because ifcvt
moves the T_REG clobbering subc/addc insn between the 'q < read' comparison
(sets T_REG) and the conditional branch (uses T_REG).