The registers are set with values before entering the function or procedure. How these are set depends on how the function or procedure was defined. There are two possibilities.
Stand alone, or explicitly defined procedures and functions
eax holds the value of the first parameter of the function or procedure if such exists.
ebx holds the address of the data block of the function or procedure. You must be careful when using ebx, for it must hold its initial value whenever you refer to a function or procedure's parameters or data in your assembler code block. Furthermore ebx must hold its initial value when exiting. The Delphi manual actually says don't touch.
ecx holds the value of the third parameter.
edx holds the second parameter value.
eax holds the result of the function, or in the case of a procedure, convention states it holds the value of any relevant error code you may define.
ebx must hold its initial value. Failure to ensure this will cause a system crash.
Object method, procedures and functions
eax holds the address of the parent object's data block. You don't need to maintain this value, however it is needed whenever you wish to access or change the values of the parent object's fields.
ebx is the same as above.
ecx holds the second parameter value.
edx holds the value of the first parameter.
On exit, the register values are as for a stand alone procedure or function.
注：64位汇编，过程或函数的前面四个传参寄存器变成了：RCX, RDX, R8, R9（或XMM0-XMM3）
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