abs/fabs/labs not builtin in C++

abs/fabs/labs not builtin in C++

[Andreas Schwab]

Why are abs, labs and fabs not builtins in C++?  A comment in cp/decl.c
claims they don't work with libg++, but i could not find any problems
after enabling them, and libg++ is obsolete anyway.


1997-12-09  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* call.c (build_over_call): Convert builtin abs, labs and fabs to
	tree-codes.

	* decl.c (init_decl_processing): Reenable abs, labs and fabs as
	builtins.

*** egcs-971207/gcc/cp/call.c.~1~	Tue Dec  9 00:33:39 1997
--- egcs-971207/gcc/cp/call.c	Tue Dec  9 11:24:31 1997
*************** build_over_call (fn, convs, args, flags)
*** 5591,5596 ****
--- 5591,5613 ----
    else
      fn = build_addr_func (fn);
  
+   /* Recognize certain built-in functions so we can make tree-codes
+      other than CALL_EXPR.  We do this when it enables fold-const.c
+      to do something useful.  */
+ 
+   if (TREE_CODE (fn) == ADDR_EXPR
+       && TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL
+       && DECL_BUILT_IN (TREE_OPERAND (fn, 0)))
+     switch (DECL_FUNCTION_CODE (TREE_OPERAND (fn, 0)))
+       {
+       case BUILT_IN_ABS:
+       case BUILT_IN_LABS:
+       case BUILT_IN_FABS:
+ 	if (converted_args == 0)
+ 	  return integer_zero_node;
+ 	return build_unary_op (ABS_EXPR, TREE_VALUE (converted_args), 0);
+       }
+ 
    fn = build_call (fn, TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))), converted_args);
    if (TREE_TYPE (fn) == void_type_node)
      return fn;
*** egcs-971207/gcc/cp/decl.c.~1~	Tue Dec  9 00:33:58 1997
--- egcs-971207/gcc/cp/decl.c	Tue Dec  9 11:23:39 1997
*************** init_decl_processing ()
*** 5263,5273 ****
  
    if (!flag_no_builtin)
      {
- #if 0 /* These do not work well with libg++.  */
        builtin_function ("abs", int_ftype_int, BUILT_IN_ABS, NULL_PTR);
        builtin_function ("fabs", double_ftype_double, BUILT_IN_FABS, NULL_PTR);
        builtin_function ("labs", long_ftype_long, BUILT_IN_LABS, NULL_PTR);
- #endif
        builtin_function ("fabsf", float_ftype_float, BUILT_IN_FABS, NULL_PTR);
        builtin_function ("fabsl", ldouble_ftype_ldouble, BUILT_IN_FABS,
  			NULL_PTR);
--- 5263,5271 ----

Re: abs/fabs/labs not builtin in C++

[Richard Henderson]

On Wed, Dec 10, 1997 at 11:15:01AM +0100, Andreas Schwab wrote:
> Why are abs, labs and fabs not builtins in C++?

Don't know about labs/fabs, but I believe the std c++ library
overloads abs.  That's not to say that we can't define the
overloads as builtins as well, but...


r~

Re: abs/fabs/labs not builtin in C++

[Joe Buck]

> Why are abs, labs and fabs not builtins in C++?  A comment in cp/decl.c
> claims they don't work with libg++, but i could not find any problems
> after enabling them, and libg++ is obsolete anyway.

If this is done, we need to make sure to provide all the proper overloads.
Essentially there should be an abs() for every builtin numeric type.