If available, use GCC 5's builtin functions for efficient integer
overflow checking. Also, add macros like INT_ADD_WRAPV that efficently
and safely compute the low-order bits of the correct answer.
A downside of these efficient functions is that they cannot be
used in constant expressions, so add macros like INT_CONST_ADD_OVERFLOW
and INT_CONST_ADD_WRAPV that can be used even in constant expressions.
* NEWS: Document the incompatible changes to INT_ADD_OVERFLOW etc.
* doc/intprops.texi (Integer Properties, Integer Type Overflow):
Document the changes.
(Wraparound Arithmetic): New section.
(Integer Range Overflow):
Put this subsection last, since it's least useful.
* lib/intprops.h (INT_CONST_ADD_OVERFLOW)
(INT_CONST_SUBTRACT_OVERFLOW, INT_CONST_MULTIPLY_OVERFLOW):
New macros, with the meaning that INT_ADD_OVERFLOW etc. used to have.
(INT_CONST_ADD_WRAPV, INT_CONST_SUBTRACT_WRAPV)
(INT_NEGATE_WRAPV, INT_CONST_MULTIPLY_WRAPV, INT_DIVIDE_WRAPV)
(INT_REMAINDER_WRAPV, _GL_INT_OP_WRAPV, _GL_EXPR_CAST)
(_GL_INT_OP_WRAPV_LONGISH, INT_ADD_WRAPV, INT_SUBTRACT_WRAPV)
(INT_MULTIPLY_WRAPV, _GL_OP_OVERFLOW, _GL_OP_WRAPV, _GL_OP_WRAPV_GENSYM):
New macros.
(INT_ADD_OVERFLOW, INT_SUBTRACT_OVERFLOW, INT_MULTIPLY_OVERFLOW):
Generate calls to GCC builtins if available, for speed.
* tests/test-intprops.c (INT_CONST_DIVIDE_OVERFLOW)
(INT_CONST_REMAINDER_OVERFLOW, INT_CONST_LEFT_SHIFT_OVERFLOW)
(INT_CONST_DIVIDE_WRAPV, INT_CONST_REMAINDER_WRAPV)
(INT_CONST_LEFT_SHIFT_WRAPV): New macros.
(main, CHECK_BINOP, CHECK_UNOP, CHECK_SUM, CHECK_PRODUCT)
(CHECK_QUOTIENT, CHECK_REMAINDER):
Test WRAPV and CONST flavors (when available) too.