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[[Category:AssemblerAssembly Language]] This page contains very basic information on the x86_64 architecture: the [[Register|register]] layout and naming and the some basic instructions. == Registers ==

* 16-bit registers using no prefix (original registers: _x) or a 'dw' suffix (added registers: r__dr__w): ax, r15dr15w* 8-bit registers using 'h' ("high byte" of 16 bits) suffix (original registers - bits 8-15: _h): ah, bh* 8-bit registers using 'l' ("low byte" of 16 bits) suffix (original registers - bits 0-7: _l) or 'b' suffix (added registers: r__b): al, bl, r15b Usage during [[Syscalls|syscall]]/function call:* First six arguments are in rdi, rsi, rdx, rcx, r8d, r9d; remaining arguments are on the stack.* For syscalls, the syscall number is in rax. For procedure calls, rax should be set to 0.* Return value is in rax.* The called routine is expected to preserve rsp,rbp, rbx, r12, r13, r14, and r15 but may trample any other registers.

Usage during syscall/function call:=== Floating-Point and SIMD Registers ===* First six arguments are in rdi, rsi, rdx, rcx, r8d, r9d; remaining arguments are on the stack* x86_64 also defines a set of large registers for floating-point and single-instruction/multiple-data (SIMD) operations. For syscallsdetails, refer to the syscall number is in rax* Return value is in rax* The called routine is expected to save rsp,rbp, rbx, r12, r13, r14, and r15 but may trample any other registersIntel or AMD documentation.

These instructions are sufficient to complete the [[SPO600 Assembler Lab]](GAS syntax):  add %r10,%r11 // add r10 and r11, put result in r11 add $5,%r10 // add 5 to r10, put result in r10 call ''label'' // call a subroutine / function / procedure cmp %r10,%r11 // compare register r10 with register r11. The comparison sets flags in the processor status register which affect conditional jumps. cmp $99,%r11 // compare the number 99 with register r11. The comparison sets flags in the processor status register which affect conditional jumps. div %r10 // divide rax by the given register (r10), places quotient into rax and remainder into rdx (rdx must be zero before this instruction) inc %r10 // increment r10 jmp ''label'' // jump to label je ''label'' // jump to label if equal jne ''label'' // jump to label if not equal jl ''label'' // jump to label if less jg ''label'' // jump to label if greater mov %r10,%r11 // move data from r10 to r11 mov $99,%r10 // put the immediate value 99 into r10 mov %r10,(%r11) // move data from r10 to address pointed to by r11 mov (%r10),%r11 // move data from address pointed to by r10 to r10 mul %r10 // multiplies rax by r10, places result in rax and overflow in rdx push %r10 // push r10 onto the stack pop %r10 // pop r10 off the stack ret // routine from subroutine (counterpart to call) syscall // invoke a syscall (in 32-bit mode, use "int $0x80" instead) Note the syntax:* [[Register]] names are prefixed by %* [[Immediate Value|Immediate values]] are prefixed by $* Indirect memory access is indicated by (parenthesis).* Hexadecimal values are indicated by a 0x prefix.* Character values are indicated by quotation marks. Escapes (such as '\n') are permitted.* Data sources are given as the first argument (mov %r10,%r11 moves FROM r10 INTO r11). For the MOV instruction:* You can append a suffix indicating the amount of data to be moved -- e.g., q for quadword (64 bits), d for doubleword (32 bits), w for word (16 bits), or b for byte (8 bits).

== References ==* CPU Instruction Set and Software Developer Manuals* For full information on * AMD: https://developer.amd.com/resources/developer-guides-manuals/ (see the x86_64 registers and instruction setAMD64 Architecture section, see particularly the ''AMD64 Architecture Programmer’s Manual Volume 3: General Purpose and System Instructions'')** Intel manuals: http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html* Web sites** http://ref.x86asm.net/** http://sandpile.org/* GAS Manual - Using as, The GNU Assembler: https://sourceware.org/binutils/docs/as/