在汇编语言中使用asm（国外英文资料）.docVIP

在汇编语言中使用asm（国外英文资料） Using asm in assembly language, you can also use C statements. That means you dont need to know where your data is in registers or memory. You need to describe the assembly instructions that appear in the machine, adding a mandatory constraint for each operand. For example, this is a method using the 68881 s fsinx directive: Asm ( fsin x % 1, % 0 : = f (result) : f (Angle)); This is the input operand when the result is output operand in C. Each has an f as its operand constraint, which means a floating point recorder. Display the operands for output; All output operands must be =. Constraints use the same statement in the machine (see constraints). Each operand is described by the operation constraint string after the C statement in parentheses. A colon will separate the first output operands and if there is a last one, the same is true. The comma separates the operands in each group. The sum of operands is generally limited to 301; This restriction may be broken in the future version of GCC. If you have no output and only input, you need to add two consecutive colon Numbers in the output. As with GCC 3.1, it may also use the symbolic name you can reference in the sink code to specify the input and output operands. These names are specified within the square brackets before the constraint string, and the % [name] can be used in the sink code instead of the percentile of the operation number. Examples of using named operands are as follows: Asm ( fsin x % [Angle], % [output] [output] = f (result) [Angle] f (Angle)); Note that the names of the symbol operands are not related to other C language identifiers. You can use any name you like, even those who now some label, but must ensure that no two identical in the same assembly symbolic name. The output operation expression must be left; The compiler can recognize it. The input operands dont need that. The compiler cannot identify the operands that have reasonable data types for the instructions. It