x86-64 Registers and Instructions

64-bit	32-bit	16-bit	8-bit	Special Purpose for functions	When calling a function	When writing a function
rax	eax	ax	ah,al	Return Value	Might be changed	Use freely
rbx	ebx	bx	bh,bl		Will not be changed	Save before using!
rcx	ecx	cx	ch,cl	4^th integer argument	Might be changed	Use freely
rdx	edx	dx	dh,dl	3^rd integer argument	Might be changed	Use freely
rsi	esi	si	sil	2^nd integer argument	Might be changed	Use freely
rdi	edi	di	sil	1^st integer argument	Might be changed	Use freely
rbp	ebp	bp	bpl	Frame Pointer	Maybe Be Careful	Maybe Be Careful
rsp	esp	sp	spl	Stack Pointer	Be Very Careful!	Be Very Careful!
r8	r8d	r8w	r8b	5^th integer argument	Might be changed	Use freely
r9	r9d	r9w	r9b	6^th integer argument	Might be changed	Use freely
r10	r10d	r10w	r10b		Might be changed	Use freely
r11	r11d	r11w	r11b		Might be changed	Use freely
r12	r12d	r12w	r12b		Will not be changed	Save before using!
r13	r13d	r13w	r13b		Will not be changed	Save before using!
r14	r14d	r14w	r14b		Will not be changed	Save before using!
r15	r15d	r15w	r15b		Will not be changed	Save before using!

"Might be changed" = "Caller saved"; "Will not be changed" = "Callee saved".

The first 8 floating point arguments are passed in registers xmm0 to xmm7.

Arithmetic	Logic	Jumps	Stack
add ⟨dest⟩ ⟨src⟩ sub ⟨dest⟩ ⟨src⟩ inc ⟨dest⟩ dec ⟨dest⟩ imul ⟨dest⟩ ⟨src⟩ div ⟨dest⟩	and ⟨dest⟩ ⟨src⟩ or ⟨dest⟩ ⟨src⟩ not ⟨dest⟩ shr ⟨dest⟩, ⟨imm⟩ shr ⟨dest⟩, cl shl ⟨dest⟩, ⟨imm⟩ shl ⟨dest⟩, cl sar ⟨dest⟩, ⟨imm⟩ sar ⟨dest⟩, cl	jmp ⟨label⟩ cmp ⟨dest⟩ ⟨src⟩ je ⟨label⟩ jne ⟨label⟩ jg ⟨label⟩ jge ⟨label⟩ jl ⟨label⟩ jle ⟨label⟩	call ⟨label⟩ ret push ⟨src⟩ pop ⟨dest⟩

⟨dest⟩ is register or memory
⟨src⟩ is register or memory or immediate
⟨imm⟩ is immediate (byte only)