README
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gojit -- pure-golang runtime code-generation
This is the result of my spending the hack day at Gophercon 2014 playing with doing JIT from golang code. This repository contains several packages:
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gojitContains the basic JIT support -- allocate executable chunks of memory, and convert them into callable golang functions.
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amd64Contains a simplistic amd64 assembler designed for use with
gojit -
bfContains a just-in-time compiler for Brainfuck that demos the above packages
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gobfContains a binary that provides a command-line interface to
bf
Using
gobf can be fetched using
go get github.com/nelhage/gojit/gobf
And then run as gobf file.bf. For some built-in examples:
$ gobf $GOPATH/src/github.com/nelhage/gojit/bf/test/hello.bf
Hello World!
$ gobf $GOPATH/src/github.com/nelhage/gojit/bf/test/hello.bf | gobf $GOPATH/src/github.com/nelhage/gojit/bf/test/rot13.bf
Uryyb Jbeyq!
Portability
This code has been tested on darwin/amd64 and linux/amd64. It is
extremely unlikely to work anywhere else.
Documentation
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Overview ¶
Package gojit contains basic support for writing JITs in golang. It contains functions for allocating byte slices in executable memory, and converting between such slices and golang function types.
Index ¶
Constants ¶
const PageSize = 4096
PageSize is the size of a memory page. The len argument to Alloc should be an integer multiple of the page size.
Variables ¶
This section is empty.
Functions ¶
func Alloc ¶
Alloc returns a byte slice of the specified length that is marked RWX -- i.e. the memory in it can be both written and executed. This is just a simple wrapper around syscall.Mmap.
len most likely needs to be a multiple of PageSize.
func Build ¶
func Build(b []byte) func()
Build returns a nullary golang function that will result in jumping into the specified byte slice. The slice should in most cases be a slice returned by Alloc, although you could also use syscall.Mmap or syscall.Mprotect directly.
func BuildCgo ¶
func BuildCgo(b []byte) func()
BuildCgo is like Build, but the resulting provided code will be called by way of the cgo runtime. This has the advantage of being much easier and safer to program against (your JIT'd code need only conform to your platform's C ABI), at the cost of significant overhead for each call into your code.
func BuildTo ¶
func BuildTo(b []byte, out interface{})
BuildTo converts a byte-slice into an arbitrary-signatured function. The out argument should be a pointer to a variable of `func' type.
Arguments to the resulting function will be passed to code using a hybrid of the GCC and 6c ABIs: The compiled code will receive, via the GCC ABI, a single argument, a void* pointing at the beginning of the 6c argument frame. For concreteness, on amd64, a func([]byte) int would result in %rdi pointing at the 6c stack frame, like so:
24(%rdi) [ return value ] 16(%rdi) [ cap(slice) ] 8(%rdi) [ len(slice) ] 0(%rdi) [ uint8* data ]
func BuildToCgo ¶
func BuildToCgo(b []byte, out interface{})
BuildToCgo is as Build, but uses cgo like BuildCGo
Types ¶
Source Files
Directories
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| Path | Synopsis |
|---|---|
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Package amd64 implements a simple amd64 assembler.
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Package amd64 implements a simple amd64 assembler. |
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Package bf implements a JIT compiler for the Brainfuck programming language.
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Package bf implements a JIT compiler for the Brainfuck programming language. |