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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 33 |
1 files changed, 24 insertions, 9 deletions
@@ -31,13 +31,8 @@ command codes. ## prerequisite knowledge -In this series, I want to *everything* that's going on to be understandable. I'm going to -need to assume some passing knowledge, so here's a quick overview of what you'll -want to know before starting. -You don't need to understand everything about each of these, just get -a general idea: +If you want to follow along with this series, you'll probably want to know about: -- the basics of programming - what a system call is - what memory is - what a compiler is @@ -56,8 +51,7 @@ decimal. - how pointers work - how floating-point numbers work -If you aren't familiar with x86-64 assembly, be sure to check out the instruction list -below. +If you're unfamiliar with x86-64 assembly, you should check out the instruction list below. ## principles @@ -99,7 +93,18 @@ x86-64 has a *gigantic* instruction set. The manual for it is over 2,000 pages long! To make things simpler, we will only use a small subset. Here are all the instructions we'll be using. If you're not familiar with -x86-64 assembly, you might want to look over these (but you don't need to understand everything). +x86-64 assembly, you might want to look over these. + +x86-64 has 16 integer registers: rax, rbx, rcx, rdx, rsp, rbp, rsi, rdi, r8, r9, r10, r11, r12, r13, r14, r15. +We will almost entirely be using the first 8 of these. +al refers to the bottom 8 bits of rax, likewise with bl, cl, dl; +ax refers to the bottom 16 bits of rax, likewise with bx, cx, dx; +eax refers to the bottom 32 bits of rax, likewise with ebx, ecx, edx. + +x86-64 also has 16 floating-point registers: xmm0 through xmm15. We'll only be using +xmm0 and xmm1. These registers can hold either four 32-bit floating-point numbers (`float`s) or +two 64-bit floating-point numbers (`double`s), but we'll only be using them to hold either one +`float` or one `double`. In the table below, `IMM64` means a 64-bit *immediate* (a constant number). `rdx:rax` refers to the 128-bit number you get by combining `rdx` and `rax`. @@ -184,6 +189,16 @@ ax bx cx dx sp bp si di │ ja IMM32 │ 0f 87 IMM32 │ jump if "above" (like jg but unsigned) │ │ jbe IMM32 │ 0f 86 IMM32 │ jump if below or equal to │ │ jae IMM32 │ 0f 83 IMM32 │ jump if above or equal to │ +│ sete al │ 0f 94 c0 │ set al to 1 if equal; 0 otherwise │ +│ setne al │ 0f 95 c0 │ set al to 1 if not equal │ +│ setl al │ 0f 9c c0 │ set al to 1 if less than │ +│ setg al │ 0f 9f c0 │ set al to 1 if greater than │ +│ setle al │ 0f 9e c0 │ set al to 1 if less than or equal to │ +│ setge al │ 0f 9d c0 │ set al to 1 if greater than or equal to│ +│ setb al │ 0f 92 c0 │ set al to 1 if below │ +│ seta al │ 0f 97 c0 │ set al to 1 if above │ +│ setbe al │ 0f 96 c0 │ set al to 1 if below or equal to │ +│ setae al │ 0f 93 c0 │ set al to 1 if above or equal to │ | movq rax, xmm0 | 66 48 0f 7e c0 | set rax to xmm0 | | movq xmm0, rax | 66 48 0f 6e c0 | set xmm0 to rax | | movq xmm1, rax | 66 48 0f 6e c8 | set xmm1 to rax | |