苹果为何将R8l用作字节寄存器而不是R8b? [英] Why does Apple use R8l for the byte registers instead of R8b?

问题描述

我在进行代码64位清理主题

╔═════════════════════╤══════════════════════════════════════════════════════╗
║ Register name       │ Description                                          ║
╠═════════════════════╪══════════════════════════════════════════════════════╣
║ R8                  │ A 64-bit register.                                   ║
╟─────────────────────┼──────────────────────────────────────────────────────╢
║ R8d                 │ A 32-bit register containing the bottom half of R8.  ║
╟─────────────────────┼──────────────────────────────────────────────────────╢
║ R8w                 │ A 16-bit register containing the bottom half of R8d. ║
╟─────────────────────┼──────────────────────────────────────────────────────╢
║ R8l (Lowercase "l") │ An 8-bit register containing the bottom half of R8w. ║
╚═════════════════════╧══════════════════════════════════════════════════════╝

使用l后缀，我首先认为它是一个long寄存器，就像GAS语法一样.

With the l suffix I first thought that it's a long register like in GAS syntax.

为什么苹果使用别人的名字?

Why is Apple using a different name from everybody else?

推荐答案

正如罗斯·里奇(Ross Ridge)的评论一样，这是因为AMD和英特尔的寄存器命名约定不同

As from Ross Ridge's comment, that's because of the difference in AMD and Intel's register naming convention

摘自《 AMD64体系结构程序员手册》，第1卷:应用程序编程

From AMD64 Architecture Programmer’s Manual, Volume 1: Application Programming

3.1.2 64位模式寄存器

在64位模式下，将八个新GPR添加到八个旧版GPR中，所有16个GPR均为64位宽，并且可访问所有寄存器的低字节.第27页的图3-3显示了64位模式下可用的GPR，标志寄存器和指令指针寄存器. GPR包括:

3.1.2 64-Bit-Mode Registers

In 64-bit mode, eight new GPRs are added to the eight legacy GPRs, all 16 GPRs are 64 bits wide, and the low bytes of all registers are accessible. Figure 3-3 on page 27 shows the GPRs, flags register, and instruction-pointer register available in 64-bit mode. The GPRs include:

• 十六个8位低字节寄存器(AL，BL，CL，DL，SIL，DIL，BPL，SPL， R8B，R9B，R10B，R11B，R12B，R13B，R14B，R15B ).
• 四个8位高字节寄存器(AH，BH，CH，DH)，仅当不使用REX前缀时才可寻址.
• 16个16位寄存器(AX，BX，CX，DX，DI，SI，BP，SP，R8W，R9W，R10W，R11W，R12W， R13W，R14W，R15W).
• 16个32位寄存器(EAX，EBX，ECX，EDX，EDI，ESI，EBP，ESP，R8D，R9D，R10D，R11D，R12D，R13D，​​R14D，R15D).
• 十六个64位寄存器(RAX，RBX，RCX，RDX，RDI，RSI，RBP，RSP，R8，R9，R10，R11，R12，R13，R14，R15).

• Sixteen 8-bit low-byte registers (AL, BL, CL, DL, SIL, DIL, BPL, SPL, R8B, R9B, R10B, R11B, R12B, R13B, R14B, R15B).
• Four 8-bit high-byte registers (AH, BH, CH, DH), addressable only when no REX prefix is used.
• Sixteen 16-bit registers (AX, BX, CX, DX, DI, SI, BP, SP, R8W, R9W, R10W, R11W, R12W, R13W, R14W, R15W).
• Sixteen 32-bit registers (EAX, EBX, ECX, EDX, EDI, ESI, EBP, ESP, R8D, R9D, R10D, R11D, R12D, R13D, R14D, R15D).
• Sixteen 64-bit registers (RAX, RBX, RCX, RDX, RDI, RSI, RBP, RSP, R8, R9, R10, R11, R12, R13, R14, R15).

与Intel®64和IA-32架构相比-软件开发人员手册

Compared to Intel® 64 and IA-32 Architectures - Software Developer’s Manual Volume 1: Basic Architecture

3.7.2.1 64位模式下的寄存器操作数

64位模式下的寄存器操作数可以是以下任意值:

3.7.2.1 Register Operands in 64-Bit Mode

Register operands in 64-bit mode can be any of the following:

• 64位通用寄存器(RAX，RBX，RCX，RDX，RSI，RDI，RSP，RBP或R8-R15)
• 32位通用寄存器(EAX，EBX，ECX，EDX，ESI，EDI，ESP，EBP或R8D-R15D)
• 16位通用寄存器(AX，BX，CX，DX，SI，DI，SP，BP或R8W-R15W)
• 8位通用寄存器:AL，BL，CL，DL，SIL，DIL，SPL，BPL和 R8L-R15L 可以使用REX前缀使用；可以使用AL，BL，CL，DL，AH，BH，CH，DH，而无需使用REX前缀.

• 64-bit general-purpose registers (RAX, RBX, RCX, RDX, RSI, RDI, RSP, RBP, or R8-R15)
• 32-bit general-purpose registers (EAX, EBX, ECX, EDX, ESI, EDI, ESP, EBP, or R8D-R15D)
• 16-bit general-purpose registers (AX, BX, CX, DX, SI, DI, SP, BP, or R8W-R15W)
• 8-bit general-purpose registers: AL, BL, CL, DL, SIL, DIL, SPL, BPL, and R8L-R15L are available using REX prefixes; AL, BL, CL, DL, AH, BH, CH, DH are available without using REX prefixes.

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