Commit 86b1f082ddd291543ca63bf474973e5b8a82ba6c
2015-10-30T13:45:26
intprops: add WRAPV and const flavors for GCC 5 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.