Content #
Input operands make values from C variables and expressions available to the assembly code. Operands are separated by commas. Each operand has this format:
[ [asmSymbolicName] ] constraint (cexpression)
asmSymbolicName #
为operand指定符号名，可在汇编代码中通过加中括号的方式来引用，比如：
%[Value]
cexpression #
This is the C variable or expression being passed to the asm statement as input.