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Subject: [Bug target/55190] New: [SH] ivopts causes loop setup bloat
Date: Sat, 03 Nov 2012 12:16:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55190

             Bug #: 55190
           Summary: [SH] ivopts causes loop setup bloat
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: olegendo@gcc.gnu.org
            Target: sh*-*-*


The following code:

struct X
{
  int a, b, c, d, e;
};

int test (X* x, unsigned int c)
{
  int s = 0;
  unsigned int i;
  for (i = 0; i < c; ++i)
    s += x[i].b;
  return s;
}

results in:
        tst     r5,r5
        bt/s    .L4
        mov     r5,r1
        shll2   r1
        add     r5,r1
        mov.l   .L9,r2
        shll2   r1
        add     #-20,r1
        shlr2   r1
        mul.l   r2,r1
        mov.l   .L10,r2
        add     #4,r4
        mov     #0,r0
        sts     macl,r1
        and     r2,r1
        add     #1,r1
.L3:
        mov.l   @r4,r2
        dt      r1
        add     #20,r4
        bf/s    .L3
        add     r2,r0
        rts
        nop
.L4:
        rts
        mov     #0,r0
.L11:
        .align 2
.L9:
        .long   214748365
.L10:
        .long   1073741823

In such cases, the loop counter setup code that seems to be produced by ivopts
can be left out, which would result in something like:

        tst     r5,r5
        bt/s    .L15
        add     #4,r4
        mov     #0,r0
.L14:
        mov.l   @r4,r1
        dt      r5
        add     #20,r4
        bf/s    .L14
        add     r1,r0
        rts
        nop
.L15:
        rts
        mov     #0,r0