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Subject: [Bug tree-optimization/56365] New: Missed opportunities for smin/smax standard name patterns
Date: Sun, 17 Feb 2013 15:27:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56365

             Bug #: 56365
           Summary: Missed opportunities for smin/smax standard name
                    patterns
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: olegendo@gcc.gnu.org


While working on a patch for PR 55303 to add signed / unsigned clipping insns
for the SH2A target, I've noticed the following (tested with -O2 on 196091 for
SH and ARM cross configs):

int test_03 (int a, int b)
{
  int r = a + b;
  if (r > 127)
    r = 127;
  else if (r < -128)
    r = -128;
  return r;
}

This will utilize smin / smax standard name patterns.

The following equivalent (if I'm not mistaken), however:

static inline int min (int a, int b) { return a < b ? a : b; }
static inline int max (int a, int b) { return a < b ? b : a; }

int test_04 (int a, int b)
{
  return max (-128, min (127, a));
}

will not expand to smin / smax patterns.


Another case is:

int test_05 (int a)
{
  if (127 <= a)
    a = 127;
  else if (a <= -128)
    a = -128;
  return a;
}

For integers this could also be done with smin / smax, but it isn't.