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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/59533] [SH] Missed cmp/pz opportunity
Date: Sun, 25 Jan 2015 17:42:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59533

--- Comment #7 from Oleg Endo <olegendo at gcc dot gnu.org> ---
If a shll is followed by a cbranch:

unsigned int
test_09_0 (int x, unsigned int y, unsigned int z)
{
  return ~(x >> 31) ? y : z;
}

        shll    r4
        bf      .L4
        mov     r6,r5
.L4:
        rts
        mov    r5,r0

it's better to use cmp/pz and invert the branch condition.
Combine is looking for the following pattern:

Failed to match this instruction:
(set (pc)
    (if_then_else (ge (reg:SI 4 r4 [ x ])
            (const_int 0 [0]))
        (label_ref:SI 17)
        (pc)))

One option could be adding a pattern like:

(define_insn_and_split "*cbranch"
  [(set (pc)
        (if_then_else (match_operand 0 "treg_set_expr")
                      (label_ref (match_operand 1))
                      (pc)))
   (clobber (reg:SI T_REG))]