[Bug tree-optimization/38865] New: missing FRE with VIEW_CONVERT_EXPR

[pinskia at gcc dot gnu dot org]

Take:
struct s { int i; };
float a (struct s *sv)
{
  sv->i = 0;
  int d = sv->i;
  return *(float*)&d;
}


float a1 (struct s *sv)
{
  sv->i = 0;
  return *(float*)&sv->i;
}

We miss that we could constant prop 0 into the VIEW_CONVERT_EXPR.
Likewise for non aliasing issues but with vectors:
#define vector __attribute__((vector_size(16) ))
struct s { vector int i; };
vector float a (struct s *sv)
{
  sv->i = (vector int){0,0,0};
  vector int d = sv->i;
  return (vector float)(d);
}


vector float a1 (struct s *sv)
{
  sv->i = (vector int){0,0,0};
  return (vector float)sv->i;
}


-- 
           Summary: missing FRE with VIEW_CONVERT_EXPR
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38865