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17.16.3 Macros to control conditional execution

There is one macro that may need to be defined for targets supporting conditional execution, independent of how they represent conditional branches.

— Macro: REVERSE_CONDEXEC_PREDICATES_P (op1, op2)

C表达式,返回真,如果条件执行断言op1,一个比较操作,为op2的反转, 反之亦然。定义该宏返回0,如果target具有条件执行断言,且不能被安全的反转。 不需要验证参数op1和op2相等,这已经被单独执行过。如果没有指定,该宏被定义为:

          #define REVERSE_CONDEXEC_PREDICATES_P (x, y) \
             (GET_CODE ((x)) == reversed_comparison_code ((y), NULL))