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Subject: [Bug target/49263] SH Target: underutilized "TST #imm, R0" instruction
Date: Mon, 27 Aug 2012 19:52:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49263

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2012-08-27
         Resolution|FIXED                       |
         AssignedTo|unassigned at gcc dot       |olegendo at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #18 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-08-27 19:51:42 UTC ---
Not quite so done, actually.  The following example case does not work
properly:


void test00 (int* x, int xb)
{
  if (! (xb & 128))
    x[0] = 0;
}

-O2 -m4:
        mov     r5,r0
        and     #128,r0
        tst     r0,r0
        bf      .L3
        mov.l   r0,@r4
.L3:
        rts    
        nop



void test01 (int* x, int xb)
{
  if (! (xb & 0x55))
    x[0] = 0;
}

-O2 -m4:
        mov     r5,r0
        and     #85,r0
        tst     r0,r0
        bf      .L7
        mov.l   r0,@r4
.L7:
        rts
        nop


It seems that combine is trying to look for the following patterns:

Failed to match this instruction:
(set (pc)
    (if_then_else (ne (zero_extract:SI (reg:SI 5 r5 [ xb ])
                (const_int 1 [0x1])
                (const_int 7 [0x7]))
            (const_int 0 [0]))
        (label_ref:SI 15)
        (pc)))


Failed to match this instruction:
(set (pc)
    (if_then_else (ne (and:SI (reg:SI 5 r5 [ xb ])
                (const_int 85 [0x55]))
            (const_int 0 [0]))
        (label_ref:SI 15)
        (pc)))



Another case that could see some improvement ...

bool test04 (int* x, int xb)
{
  return ! (xb & 0x55);
}

-O2 -m4 (OK):
        mov     r5,r0
        tst     #85,r0
        rts
        movt    r0


bool test02 (int* x, int xb)
{
  return ! (xb & (1 << 6));
}

-O2 -m4 (NG):
        mov     r5,r0
        mov     #-6,r1
        shld    r1,r0
        xor     #1,r0
        rts
        and     #1,r0