This is a personal fork of Avo. You probably don't want to depend on this.
Generate x86 Assembly with Go
avo makes high-performance Go assembly easier to write, review and maintain. The avo package presents a familiar assembly-like interface that simplifies development without sacrificing performance:
- Use Go control structures for assembly generation;
avoprograms are Go programs - Register allocation: write functions with virtual registers and
avoassigns physical registers for you - Automatically load arguments and store return values: ensure memory offsets are correct for complex structures
- Generation of stub files to interface with your Go package
For more about avo:
- Introductory talk "Better
x86Assembly Generation with Go" at dotGo 2019 (slides) - Longer tutorial at Gophercon 2019 showing a highly-optimized dot product (slides)
- Watch Filippo Valsorda live code the rewrite of
filippo.io/edwards25519assembly withavo - Explore projects using
avo - Discuss
avoand general Go assembly topics in the #assembly channel of Gophers Slack
Note: APIs subject to change while avo is still in an experimental phase. You can use it to build real things but we suggest you pin a version with your package manager of choice.
Install avo with go get:
$ go get -u honnef.co/go/avo
avo assembly generators are pure Go programs. Here's a function that adds two uint64 values:
//go:build ignore
package main
import . "honnef.co/go/avo/build"
func main() {
TEXT("Add", NOSPLIT, "func(x, y uint64) uint64")
Doc("Add adds x and y.")
x := Load(Param("x"), GP64())
y := Load(Param("y"), GP64())
ADDQ(x, y)
Store(y, ReturnIndex(0))
RET()
Generate()
}go run this code to see the assembly output. To integrate this into the rest of your Go package we recommend a go:generate line to produce the assembly and the corresponding Go stub file.
//go:generate go run asm.go -out add.s -stubs stub.goAfter running go generate the add.s file will contain the Go assembly.
// Code generated by command: go run asm.go -out add.s -stubs stub.go. DO NOT EDIT.
#include "textflag.h"
// func Add(x uint64, y uint64) uint64
TEXT ·Add(SB), NOSPLIT, $0-24
MOVQ x+0(FP), AX
MOVQ y+8(FP), CX
ADDQ AX, CX
MOVQ CX, ret+16(FP)
RETThe same call will produce the stub file stub.go which will enable the function to be called from your Go code.
// Code generated by command: go run asm.go -out add.s -stubs stub.go. DO NOT EDIT.
package add
// Add adds x and y.
func Add(x uint64, y uint64) uint64See the examples/add directory for the complete working example.
See examples for the full suite of examples.
Sum a slice of uint64s:
func main() {
TEXT("Sum", NOSPLIT, "func(xs []uint64) uint64")
Doc("Sum returns the sum of the elements in xs.")
ptr := Load(Param("xs").Base(), GP64())
n := Load(Param("xs").Len(), GP64())
Comment("Initialize sum register to zero.")
s := GP64()
XORQ(s, s)
Label("loop")
Comment("Loop until zero bytes remain.")
CMPQ(n, Imm(0))
JE(LabelRef("done"))
Comment("Load from pointer and add to running sum.")
ADDQ(Mem{Base: ptr}, s)
Comment("Advance pointer, decrement byte count.")
ADDQ(Imm(8), ptr)
DECQ(n)
JMP(LabelRef("loop"))
Label("done")
Comment("Store sum to return value.")
Store(s, ReturnIndex(0))
RET()
Generate()
}The result from this code generator is:
// Code generated by command: go run asm.go -out sum.s -stubs stub.go. DO NOT EDIT.
#include "textflag.h"
// func Sum(xs []uint64) uint64
TEXT ·Sum(SB), NOSPLIT, $0-32
MOVQ xs_base+0(FP), AX
MOVQ xs_len+8(FP), CX
// Initialize sum register to zero.
XORQ DX, DX
loop:
// Loop until zero bytes remain.
CMPQ CX, $0x00
JE done
// Load from pointer and add to running sum.
ADDQ (AX), DX
// Advance pointer, decrement byte count.
ADDQ $0x08, AX
DECQ CX
JMP loop
done:
// Store sum to return value.
MOVQ DX, ret+24(FP)
RETFull example at examples/sum.
For demonstrations of avo features:
- args: Loading function arguments.
- returns: Building return values.
- complex: Working with
complex{64,128}types. - data: Defining
DATAsections. - ext: Interacting with types from external packages.
- pragma: Apply compiler directives to 8000 generated functions.
Implementations of full algorithms:
- sha1: SHA-1 cryptographic hash.
- fnv1a: FNV-1a hash function.
- dot: Vector dot product.
- md5x16: AVX-512 accelerated MD5.
- geohash: Integer geohash encoding.
- stadtx:
StadtXhash port from dgryski/go-stadtx.
Popular projects1 using avo:
The Go programming language
Optimized Go Compression Packages
[mirror] Go supplementary cryptography libraries
Reed-Solomon Erasure Coding in Go
Universal Utilities for Go
CIRCL: Cloudflare Interoperable Reusable Cryptographic Library
Go library providing algorithms optimized to leverage the characteristics of modern CPUs
XXH3 algorithm in Go
Pure Go implementation of BLAKE3 with AVX2 and SSE4.1 acceleration
An AVX-512 accelerated implementation of the BLAKE3 cryptographic hash function
See the full list of projects using avo.
Contributions to avo are welcome:
- Feedback from using
avoin a real project is incredibly valuable. Consider porting an existing project toavo. - Submit bug reports to the issues page.
- Pull requests accepted. Take a look at outstanding issues for ideas (especially the "good first issue" label).
- Join us in the #assembly channel of Gophers Slack.
Inspired by the PeachPy and asmjit projects. Thanks to Damian Gryski for advice, and his extensive library of PeachPy Go projects.
avo is available under the BSD 3-Clause License.
Footnotes
-
Projects drawn from the
avothird-party test suite. Popularity estimated from Github star count collected on Feb 1, 2026. ↩