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diff --git a/docs/language.md b/docs/language.md index 96f534b..8c10eb4 100644 --- a/docs/language.md +++ b/docs/language.md @@ -1,10 +1,10 @@ # hdass language reference -This is the language reference. hdass transpiles to x86-64 (NASM or fasm, `-t nasm`/`-t fasm`) and AArch64 (`-t arm64`); for which target supports what, the portable [`logical_registers`](#logical_registers) model, and the per-architecture syscall ABIs, see [Targets](targets.md). New here? Start with [Getting started](getting-started.md). Pipeline: `lex → parse → analyze → emit`. +this is the language reference. hdass transpiles to x86-64 (nasm or fasm, `-t nasm`/`-t fasm`) and aarch64 (`-t arm64`); for which target supports what, the portable [`logical_registers`](#logical_registers) model, and the per-architecture syscall abis, see [targets](targets.md). new here? start with [getting started](getting-started.md). pipeline: `lex → parse → analyze → emit`. -The examples below use x86-64 register names. The output isn't tied to an OS, but the examples and toolchain here target Linux (ELF, `ld`). +the examples below use x86-64 register names. the output isn't tied to an os, but the examples and toolchain here target linux (elf, `ld`). -## A first program +## a first program ```hdass [entry: main] @@ -29,36 +29,36 @@ proc main } ``` -Writes `type shi.` to stdout and exits. +writes `type shi.` to stdout and exits. -## Comments +## comments ```hdass rax = 1 // line /* block */ ``` -## Directives +## directives -Top-level `[key: value]` (or bare `[key]`), configuring the whole program. +top-level `[key: value]` (or bare `[key]`), configuring the whole program. -| Directive | Meaning | +| directive | meaning | | --- | --- | -| `[bits: 64]` / `[bits: 32]` / `[bits: 16]` | Target bitness. Default 64. | -| `[entry: NAME]` | Makes procedure `NAME` the entry point. | -| `[enable: NAME]` | Turns on an [extension](#extensions). | -| `[format: bin]` / `[format: elf]` | Output a flat binary instead of an ELF object. Default elf. | -| `[org: 0x7C00]` | Set the load address of a flat binary. | -| `[boot]` | Pad a flat binary to 510 bytes and append the `0xAA55` boot signature. | +| `[bits: 64]` / `[bits: 32]` / `[bits: 16]` | target bitness. default 64. | +| `[entry: NAME]` | makes procedure `NAME` the entry point. | +| `[enable: NAME]` | turns on an [extension](#extensions). | +| `[format: bin]` / `[format: elf]` | output a flat binary instead of an elf object. default elf. | +| `[org: 0x7C00]` | set the load address of a flat binary. | +| `[boot]` | pad a flat binary to 510 bytes and append the `0xAA55` boot signature. | -The last three build a raw binary instead of a linked ELF, enough for an x86 -boot sector. In `bin` format there are no sections or exported symbols, and code -comes first so execution starts at the origin. Unknown keys, a bad `bits` value, +the last three build a raw binary instead of a linked elf, enough for an x86 +boot sector. in `bin` format there are no sections or exported symbols, and code +comes first so execution starts at the origin. unknown keys, a bad `bits` value, and unknown extensions are errors. -## Constants and data +## constants and data -`const` names a constant integer expression — integer literals, character literals, other constants, a leading `-`, and `+` `-` `*` `/`. Integers are decimal, `0x` hex, or `0b` binary (these forms work anywhere an integer does). `data` puts a string in `.data`; the name is its address and `.len` is its length in bytes. +`const` names a constant integer expression — integer literals, character literals, other constants, a leading `-`, and `+` `-` `*` `/`. integers are decimal, `0x` hex, or `0b` binary (these forms work anywhere an integer does). `data` puts a string in `.data`; the name is its address and `.len` is its length in bytes. ```hdass const STDOUT = 1 @@ -67,9 +67,9 @@ const AREA = 8 * 6 // 48 data message = "type shi.\n" // message -> address, message.len -> 10 ``` -## Enums and structs +## enums and structs -Both describe compile-time values reached with `Name.member`, which folds to an integer. +both describe compile-time values reached with `Name.member`, which folds to an integer. `enum` names a set of constants numbered from 0: @@ -84,7 +84,7 @@ enum Status rax = Status.Fail // mov rax, 2 ``` -`struct` describes a packed memory layout (no padding). Fields are `name` or `name: size`, where size defaults to `qword`. `Name.field` is the field's byte offset, and `Name.size` is the total size. +`struct` describes a packed memory layout (no padding). fields are `name` or `name: size`, where size defaults to `qword`. `Name.field` is the field's byte offset, and `Name.size` is the total size. ```hdass struct Point @@ -98,11 +98,11 @@ rsi += Point.y // add rsi, 8 rax = Point.size // mov rax, 17 ``` -A struct is layout only — it allocates nothing. Pair it with a `stack` buffer sized by `Name.size` and pointer arithmetic (see [examples/records.hdass](../examples/records.hdass)). +a struct is layout only — it allocates nothing. pair it with a `stack` buffer sized by `Name.size` and pointer arithmetic (see [examples/records.hdass](../examples/records.hdass)). -## Procedures +## procedures -`proc` groups a body. Parameters name registers — `value` below is `rdi`. +`proc` groups a body. parameters name registers — `value` below is `rdi`. ```hdass proc print_number(value: rdi) @@ -111,13 +111,13 @@ proc print_number(value: rdi) } ``` -Each procedure ends with `ret`, except the entry point. `[entry: NAME]` exports `NAME` with `global` and drops its `ret`, so it must end the program itself (an exit syscall). Link with `ld -e NAME`. +each procedure ends with `ret`, except the entry point. `[entry: NAME]` exports `NAME` with `global` and drops its `ret`, so it must end the program itself (an exit syscall). link with `ld -e NAME`. -## Registers +## registers -Written by their architecture names — `rax`–`rdi`, `rbp`, `rsp`, `r8`–`r15` — and their sub-registers (`al`, `ax`, `eax`, `dl`, …), which imply a store's size. The [`logical_registers`](#logical_registers) extension adds `r1`–`r14`. The segment registers (`cs ds es fs gs ss`) and control registers (`cr0 cr2 cr3 cr4`) are also recognised, for systems code that sets up segments or switches CPU modes. +written by their architecture names — `rax`–`rdi`, `rbp`, `rsp`, `r8`–`r15` — and their sub-registers (`al`, `ax`, `eax`, `dl`, …), which imply a store's size. the [`logical_registers`](#logical_registers) extension adds `r1`–`r14`. the segment registers (`cs ds es fs gs ss`) and control registers (`cr0 cr2 cr3 cr4`) are also recognised, for systems code that sets up segments or switches cpu modes. -## Statements +## statements ```hdass rax = SYS_WRITE // mov @@ -135,9 +135,9 @@ print_number(r12) // call; args go into the callee's parameter registers stack buf[Point.size] // stack buffer (size is any constant); buf is its base address ``` -## Control flow (`if` / `else` / `while`) +## control flow (`if` / `else` / `while`) -`if <expr> <cmp> <expr>` guards either the single next statement or a `{ }` block, and an optional `else` takes its own statement or block. `else if` chains because the `else` body is itself a statement. Comparisons are `==` `!=` `<` `<=` `>` `>=`; a float compare needs an `xmm` register on the left (see [Floating point](#floating-point)). +`if <expr> <cmp> <expr>` guards either the single next statement or a `{ }` block, and an optional `else` takes its own statement or block. `else if` chains because the `else` body is itself a statement. comparisons are `==` `!=` `<` `<=` `>` `>=`; a float compare needs an `xmm` register on the left (see [floating point](#floating-point)). ```hdass if rax > rbx @@ -151,7 +151,7 @@ else rdi = -1 ``` -`while <expr> <cmp> <expr>` runs its statement or `{ }` block for as long as the condition holds, testing it before each pass. It is the same condition as `if`, and desugars to a label, the test, the body, and a jump back — the `loop:`/`goto` you would write by hand. Use `goto` to break out early. +`while <expr> <cmp> <expr>` runs its statement or `{ }` block for as long as the condition holds, testing it before each pass. it is the same condition as `if`, and desugars to a label, the test, the body, and a jump back — the `loop:`/`goto` you would write by hand. use `goto` to break out early. ```hdass rbx = 0 @@ -162,22 +162,22 @@ while rcx > 0 } ``` -An optional `.name` right after `while` names the loop's generated labels, so they read as `.name` (top) and `.name_end` (exit) instead of the anonymous `.while_N` — handy for finding a loop in the emitted assembly. Give nested loops distinct names. +an optional `.name` right after `while` names the loop's generated labels, so they read as `.name` (top) and `.name_end` (exit) instead of the anonymous `.while_N` — handy for finding a loop in the emitted assembly. give nested loops distinct names. ```hdass while .countdown rcx > 0 // emits `.countdown:` … `jmp .countdown` … `.countdown_end:` rcx -= 1 ``` -A **conditional select** picks one of two register values without a branch: `dst = a if <cond> else b`. It lowers to `csel` on AArch64 (one instruction) and `cmov` on x86 (a default move plus a conditional move, arranged so `dst` may safely alias either source). Both sources must be registers. +a **conditional select** picks one of two register values without a branch: `dst = a if <cond> else b`. it lowers to `csel` on aarch64 (one instruction) and `cmov` on x86 (a default move plus a conditional move, arranged so `dst` may safely alias either source). both sources must be registers. ```hdass r3 = r1 if r1 > r2 else r2 // r3 = max(r1, r2), branchless ``` -## Dereference (`^`) +## dereference (`^`) -`^reg` is the memory at the address in `reg` — NASM's `[reg]`. On the left of `=` it stores there. The store width comes from the value operand, so a sized sub-register picks the size: +`^reg` is the memory at the address in `reg` — nasm's `[reg]`. on the left of `=` it stores there. the store width comes from the value operand, so a sized sub-register picks the size: ```hdass ^rsi = rdx // mov [rsi], rdx (qword) @@ -185,7 +185,7 @@ r3 = r1 if r1 > r2 else r2 // r3 = max(r1, r2), branchless ^rsi = eax // mov [rsi], eax (dword) ``` -A leading size keyword sets the width explicitly. It down-converts a full register to the matching sub-register, and gives an immediate a width NASM would otherwise reject: +a leading size keyword sets the width explicitly. it down-converts a full register to the matching sub-register, and gives an immediate a width nasm would otherwise reject: ```hdass ^byte rsi = rdx // mov byte [rsi], dl (rdx -> its low byte) @@ -195,7 +195,7 @@ A leading size keyword sets the width explicitly. It down-converts a full regist ^byte rsi = 10 // mov byte [rsi], 10 ``` -`^reg` is also a value — it loads from that address. A size keyword loads a narrower value and zero-extends it into the target: +`^reg` is also a value — it loads from that address. a size keyword loads a narrower value and zero-extends it into the target: ```hdass rax = ^rsi // mov rax, [rsi] @@ -204,7 +204,7 @@ rcx = ^dword rsi // mov ecx, [rsi] (32-bit load zero-extends) rdx = ^rsi + 4 // load, then add 4 ``` -`^signed` before the size sign-extends instead, so a narrower value keeps its sign in the full register. It needs a `byte`, `word`, or `dword` size (a full-width load has nothing to extend): +`^signed` before the size sign-extends instead, so a narrower value keeps its sign in the full register. it needs a `byte`, `word`, or `dword` size (a full-width load has nothing to extend): ```hdass rax = ^signed byte rsi // movsx rax, byte [rsi] @@ -212,9 +212,9 @@ rbx = ^signed word rsi // movsx rbx, word [rsi] rcx = ^signed dword rsi // movsxd rcx, dword [rsi] ``` -## Raw instructions +## raw instructions -Any statement that isn't an assignment, label, call or keyword is emitted as a bare instruction: a mnemonic and its operands, written in hdass's own operand syntax. This is the escape hatch for everything outside the assignment and control-flow model: `int`, `hlt`, `cli`/`sti`, `lgdt`, port I/O, the mode switch. Operands are the usual registers, immediates, constants and `^memory`, and share the mnemonic's line. +any statement that isn't an assignment, label, call or keyword is emitted as a bare instruction: a mnemonic and its operands, written in hdass's own operand syntax. this is the escape hatch for everything outside the assignment and control-flow model: `int`, `hlt`, `cli`/`sti`, `lgdt`, port i/o, the mode switch. operands are the usual registers, immediates, constants and `^memory`, and share the mnemonic's line. ```hdass cli @@ -225,19 +225,19 @@ cr0 = eax // an ordinary move; segment/control regs work with `=` too hlt ``` -Mnemonics pass straight through, so a typo is reported by the assembler. Operands render through the same path as everywhere else, so an instruction is as portable as the rest of the language, though the mnemonics themselves are architecture-specific. +mnemonics pass straight through, so a typo is reported by the assembler. operands render through the same path as everywhere else, so an instruction is as portable as the rest of the language, though the mnemonics themselves are architecture-specific. -## Expressions +## expressions -Assignment values and `if` operands: registers, integers, chars (`'0'`), constants, data names, member access (`data.len`), and `+` `-` `*` `/` `%`. Operators are left-associative and each right-hand operand must be a single term, so `a * b + c` works but `a + b * c` (a nested right operand) doesn't yet. +assignment values and `if` operands: registers, integers, chars (`'0'`), constants, data names, member access (`data.len`), and `+` `-` `*` `/` `%`. operators are left-associative and each right-hand operand must be a single term, so `a * b + c` works but `a + b * c` (a nested right operand) doesn't yet. -A leading `-` negates a term (`rax = -5`, `rbx = rax + -3`, `const OFFSET = -8`). It only applies to values that fold to a constant, so it emits a negative immediate; negating a register (`-rbx`) is not supported. +a leading `-` negates a term (`rax = -5`, `rbx = rax + -3`, `const OFFSET = -8`). it only applies to values that fold to a constant, so it emits a negative immediate; negating a register (`-rbx`) is not supported. -## Extensions +## extensions ### logical_registers -Uniform names for the general-purpose registers, so you don't juggle the irregular `rax`/`rbx`/`rsi`/… spellings. `r1`–`r14` map to: +uniform names for the general-purpose registers, so you don't juggle the irregular `rax`/`rbx`/`rsi`/… spellings. `r1`–`r14` map to: | `r1` | `r2` | `r3` | `r4` | `r5` | `r6` | `r7` | `r8` | `r9` | `r10` | `r11` | `r12` | `r13` | `r14` | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | @@ -251,7 +251,7 @@ r4 = r10 // mov rdx, r11 r6 += r1 // add rdi, rax ``` -A `.8`/`.16`/`.32`/`.64` suffix selects the width, mapping to the sub-register: +a `.8`/`.16`/`.32`/`.64` suffix selects the width, mapping to the sub-register: ```hdass r1.8 // al @@ -261,18 +261,18 @@ r1.64 // rax ^byte rsi = r4 // mov byte [rsi], dl (r4 -> rdx -> dl) ``` -Arch `r8`–`r15` share the `rN` spelling, so with the extension on a bare `r8` is the *logical* register (which is arch `r9`). Reach arch `r8`–`r15` through logical `r7`–`r14`. Architecture names like `rax` and `rsi` still work everywhere. +arch `r8`–`r15` share the `rN` spelling, so with the extension on a bare `r8` is the *logical* register (which is arch `r9`). reach arch `r8`–`r15` through logical `r7`–`r14`. architecture names like `rax` and `rsi` still work everywhere. -## Floating point +## floating point -Floating-point values live in the SSE registers `xmm0`–`xmm15` (double precision). Float literals like `3.14` are placed in `.data` and loaded for you. +floating-point values live in the sse registers `xmm0`–`xmm15` (double precision). float literals like `3.14` are placed in `.data` and loaded for you. ```hdass xmm0 = 3.5 // movsd from a .data slot xmm0 *= xmm1 // += -= *= /= -> addsd subsd mulsd divsd ``` -An `=` between a float register and a general-purpose register converts: +an `=` between a float register and a general-purpose register converts: ```hdass xmm0 = rax // int -> float (cvtsi2sd) @@ -293,9 +293,9 @@ if xmm0 > 4.0 goto escaped ``` -See [examples/mandelbrot.hdass](../examples/mandelbrot.hdass) for a float program. Not yet supported: mixing floats and ints in one expression, and printing floats. +see [examples/mandelbrot.hdass](../examples/mandelbrot.hdass) for a float program. not yet supported: mixing floats and ints in one expression, and printing floats. -## Building a program +## building a program ```bash hdass program.hdass -o program.asm # nasm (default) @@ -304,7 +304,7 @@ ld -e main program.o -o program ./program ``` -Or target fasm with `-t fasm`, which assembles in one step: +or target fasm with `-t fasm`, which assembles in one step: ```bash hdass -t fasm program.hdass -o program.asm @@ -312,7 +312,7 @@ fasm program.asm program.o ld -e main program.o -o program ``` -For `-t arm64` and the full toolchain (including the AArch64 cross-assembler and qemu), see [Getting started](getting-started.md); the [README](../README.md) has the Docker setup. +for `-t arm64` and the full toolchain (including the aarch64 cross-assembler and qemu), see [getting started](getting-started.md); the [readme](../README.md) has the docker setup. -## Some stinkies -Clobbering is your responsibility: `syscall` trashes `rcx` and `r11`, while a callee can trash any registers it touches, so nothing is saved automatically. `examples/fibonacci.hdass`, for example, keeps its counter in `r15` for this reason. Register widths must also match, meaning something like `rax = r1.8` would become `mov rax, al`, which will not assemble. Division clobbers extra registers: `/` `%` and their `=` forms use `idiv` through `rax:rdx`, so both are overwritten regardless of the destination. The divisor can be anything — a register, a constant, or an immediate — but an immediate or an `rax`/`rdx` divisor is first copied into `r11`, so those also clobber `r11`. Labels and procedures become plain assembler symbols, so avoid names the target assembler reserves: `loop`, for instance, is an instruction mnemonic that fasm rejects as a label (nasm allows it). Finally, the entry procedure has no `ret`; it should end with an exit syscall. +## some stinkies +clobbering is your responsibility: `syscall` trashes `rcx` and `r11`, while a callee can trash any registers it touches, so nothing is saved automatically. `examples/fibonacci.hdass`, for example, keeps its counter in `r15` for this reason. register widths must also match, meaning something like `rax = r1.8` would become `mov rax, al`, which will not assemble. division clobbers extra registers: `/` `%` and their `=` forms use `idiv` through `rax:rdx`, so both are overwritten regardless of the destination. the divisor can be anything — a register, a constant, or an immediate — but an immediate or an `rax`/`rdx` divisor is first copied into `r11`, so those also clobber `r11`. labels and procedures become plain assembler symbols, so avoid names the target assembler reserves: `loop`, for instance, is an instruction mnemonic that fasm rejects as a label (nasm allows it). finally, the entry procedure has no `ret`; it should end with an exit syscall. |