[Bug tree-optimization/17616] New: Micro-optimize tree_code_class

[kazu at cs dot umass dot edu]

We can put IS_EXPR_CODE_CLASS items first in tree_code_class so that
IS_EXPR_CODE_CLASS can be implemented with a single assembly instruction.

That is, the suggested order would be

  tcc_reference,   /* A reference to storage.  */
  tcc_comparison,  /* A comparison expression.  */
  tcc_unary,       /* A unary arithmetic expression.  */
  tcc_binary,      /* A binary arithmetic expression.  */
  tcc_statement,   /* A statement expression, which have side effects
                      but usually no interesting value.  */
  tcc_expression,  /* Any other expression.  */
  tcc_exceptional, /* An exceptional code (fits no category).  */
  tcc_constant,    /* A constant.  */
  tcc_type,        /* A type object code.  */
  tcc_declaration  /* A declaration (also serving as variable refs).  */

Currently, IS_EXPR_CODE_CLASS is effectively implemented as (CLASS - 4) <= 5.

After reordering, we can do CLASS <= 5.

-- 
           Summary: Micro-optimize tree_code_class
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17616