限制符主要用来决定操作数的寻址方式。

Constraints are primarily used to decide the addressing modes for operands.

youdao

但，我们只花了很少的篇幅叙述限制符。

But we've said little about constraints.

youdao

当操作指定了“r”限制符，那么操作数将会被存储在通用寄存器内。

When operands are specified using this constraint, they get stored in General Purpose Registers(GPR).

youdao