[Bug middle-end/28075] New: gimplifier introduces unnecessary type conversions

[rguenth at gcc dot gnu dot org]

typedef struct {
  double min;
  double max;
} interval;
inline interval add(interval x, interval y)
{
  interval r;
  r.min = x.min + y.min;
  r.max = x.max + y.max;
  return r;
}
interval foo (interval a, interval b, interval c)
{
  return add (a, add (b, c));
}

for the temporary for gimplifying the nested call to add, the gimplifier
introduces a temporary of type TYPE_MAIN_VARIANT (interval), which survives
as added casts.

This happens here:

static inline tree
create_tmp_from_val (tree val)
{
  return create_tmp_var (TYPE_MAIN_VARIANT (TREE_TYPE (val)), get_name (val));
}

in the optimized dump we still have

foo (a, b, c)
{
  double r$min;
  double r$min;
  double a$max;
  double a$min;
  struct interval y;
  struct
  {
    double min;
    double max;
  } D.1542;

<bb 2>:
  a$max = a.max;
  a$min = a.min;
  r$min = b.min + c.min;
  D.1542.max = b.max + c.max;
  D.1542.min = r$min;
  y = (struct interval) D.1542;
  r$min = y.min + a$min;
  <retval>.max = y.max + a$max;
  <retval>.min = r$min;
  return <retval>;

}

by simply removing this TYPE_MAIN_VARAINT there we end up with two
temporary structures less:

Analyzing Edge Insertions.
foo (a, b, c)
{
  double r$min;

<bb 2>:
  r$min = b.min + c.min + a.min;
  <retval>.max = b.max + c.max + a.max;
  <retval>.min = r$min;
  return <retval>;

}


-- 
           Summary: gimplifier introduces unnecessary type conversions
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, memory-hog, compile-time-hog
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28075