x86-64-integer-registers.md

x86-64 Integer Registers

#	64-bit	32-bit	16-bit	8-bit
1	%rax	%eax	%ax	%al	Return value
2	%rbx	%ebx	%bx	%bl	Callee saved
3	%rcx	%ecx	%cx	%cl	4th argument
4	%rdx	%edx	%dx	%dl	3th argument
5	%rsi	%esi	%si	%sil	2nd argument
6	%rdi	%edi	%di	%dil	1st argument
7	%rbp	%ebp	%bp	%bpl	Callee saved
8	%rsp	%esp	%sp	%spl	Stack pointer
9	%r8	%r8d	%r8w	%r8b	5th argument
10	%r9	%r9d	%r9w	%r9b	6th argument
11	%r10	%r10d	%r10w	%r10b	Caller saved
12	%r11	%r11d	%r11w	%r11b	Caller saved
13	%r12	%r12d	%r12w	%r12b	Callee saved
14	%r13	%r13d	%r13w	%r13b	Callee saved
15	%r14	%r14d	%r14w	%r14b	Callee saved
16	%r15	%r14d	%r14w	%r15b	Callee saved