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Keeping up with the Gophers
A brief history of gccgo, improvements, and the future
Chris Manghane
Google Gopher | Compilers and Toolchains
* gccgo: "The Other Go Compiler"
- Written and maintained by Ian Lance Taylor (released November 2009)
2010-01-26 Ian Lance Taylor <>
* MAINTAINERS: Add myself as Go frontend maintainer.
- Compiler frontend for the Go language written in C++
.image keeping-up/gccgo_structure.png 320 _
* gccgo: The Go Team didn't know
"Ian just showed up at our door with a fully working compiler" ~ probably Rob
.html keeping-up/gource_explosion.html
* Why write a Go compiler in C++?
* rationale: architecture support
- cmd/gc (2009) targets 4 major architectures: i386, amd64, ARM, and IBM POWER
- gcc (4.3, 2009) targets 45 architectures officially, 28 unofficially
- leveraging gcc => minimal work to support Go on existing architectures
* rationale: code generation
- gcc has ~30 years of work put into code analysis and optimization
- cmd/gc has only recently focused on code generation (khr's SSA work)
- leveraging gcc => minimal work to produce optimized binaries
* rationale: technical honesty
- "Keeping each other honest"
- Distinct implementations => Inconsistencies in specification and implementations
- Users have options when an implementation lacks features
- Compilers seek feature parity => Compilers learn from each other
- Compilers generate better binaries => Virtuous cycle
* gccgo improvements through a telescope
* gofrontend: no dependency on gcc
- gcc implements gofrontend's backend interface
gofrontend (gcc/go/gofrontend/
.code keeping-up/backend_interface.diff
backend (gcc/go/
.code keeping-up/cst.gcc
* gccgo: builds the `go` tool
- One way to build code across multiple compilers
.code keeping-up/go_build.log
* gofrontend: basic escape analysis
- Implementation of _Escape_analysis_for_Java_ by JD Choi
.code keeping-up/escape.go
Connection Graph
.image keeping-up/escape.png
* Keeping up
* gccgo: runtime and garbage collector parity
- gccgo runtime is a modified version of Go 1.3 runtime
- Go 1.4 runtime was rewritten in Go
- Go 1.4 changed GC type info
* beyond gccgo: compiler stack maps
- Stack map records locations of live values at a certain address
- Allows Garbage Collector to be precise about types on stack
- Enables contiguous stacks to readjust copied pointers
- Little support in C compilers: gcc has no support, LLVM support is WIP
* llvmgo: another "other Go compiler"
- gofrontend provides backend interface LLVM can implement
- LLVM byte code is trusted in secure environments such as PNaCl
- Run native Go in the web
* OS support: OSX and Windows
- gccgo support on not unixes
- Expert needed