LAS16-106: GNU Toolchain Development Lifecycle

GNU Toolchain LifecycleRyan S. Arnold

ENGINEERS AND DEVICESWORKING TOGETHER




A man builds a fine house; and now he has a master, and a task for life; he is to furnish,

watch, show it, and keep it in repair, the rest of his days

- Ralph Waldo Emerson



Wrong!


GNU/Linux Distribution : (Distro) is a formally supported collection of interoperable

programs.

These programs have been quality and integration tested in order to guarantee that

they are compatible.



http://www.ubuntu.com/info/release-end-of-lifehttps://wiki.ubuntu.com/LTS

http://www.ubuntu.com/info/release-end-of-life


https://wiki.ubuntu.com/LTS


http://www.ubuntu.com/info/release-end-of-lifehttps://wiki.ubuntu.com/LTS



https://wiki.ubuntu.com/LTS


https://access.redhat.com/articles/3078https://access.redhat.com/support/policy/updates/errata/

RHEL6.0 GA 2010-11-09RHEL6.8 - 2016-05-10RHEL7.0 GA - 2014-06-09RHEL7.2 - 2015-11-19 (AArch64)

https://access.redhat.com/articles/3078

https://access.redhat.com/support/policy/updates/errata/




Protip: Submit Early & Submit Often





Toolchain Lifecycle - Linear Progression●Idea conception (micro-

architecture)●ISA●KABI (contract with user-space)●Kernel enablement●Platform identification●KABI implementation●Kernel upstreaming●ABI (binary contract between

programs)

●GNU Toolchain Implementation●Platform identification●ASM Instruction support●Codegen●Optimization●GNU Toolchain Upstreaming●Linux Distribution Adoption●Customer’s Hands●Linux Distro updates.


Wrong!


Idea Conception

Distro Adoption

KernelEnablement

CompilerEnablement

ToolchainUpstreaming





Phases●Phase 0 - Legal & Branding●Phase 1 - Platform Enablement●Phase 2 - ABI Enablement●Phase 3 - Optimization●Phase 4 - Distro Adoption


Phase 0 - Legal and Branding


Danger! If your legal dept is dragging their feet on approving upstream contribution your

schedule is in jeopardy.



Phase 1 - Platform Enablement


ISA - Instruction Set Architecture


It is a cardinal sin to not implement all required parts of the ISA


Models


Linux Kernel Platform Enablement



www.kernel.org/category/releases.html


Assembler, Linker & Compiler Microarch Identification


GCC Instruction-Set & Cost Model


Danger! Sometimes early enablement might give away details of the processor, such as information about the pipeline bandwidth.



Glibc Platform Identification



Protip: Get the KABI enablement code upstream as soon as possible!


Rev 1 Hardware


Phase 3 - ABI Enablement


Using The Existing ABI


Danger! You implemented all required parts of the ISA right? If not, you’ve defined a new ABI

that you have to implement.


Protip: Don’t use an ABI change as a way to squeeze out more performance (unless it

benefits all microarch variants)


New ABI? Really?


It is a cardinal sin to release binaries compiled with a pre-release ABI into the wild.


Danger! Just because you proposed the change doesn’t mean you get to own the ABI.


GCC, Linker, and Assembler ABI Changes


Listen to your patch reviewers and implement changes requested or your update patches will

be ignored.


Danger! If you don’t respect the opinion of the person who will be maintaining your software,

then your contribution isn’t going to be respected.


Protip: Drop what you’re doing and turn around a patch re-spin as soon as possible

after a maintainer has reviewed your patch.


Protip: You might be asked to implement a generic solution in place of a number of arch-

specific implementations. Do it!


Glibc ABI Changes


If you’re implementing a glibc ABI change/addition you need a complete release

cycle for evaluation.


Phase 3 - Upstreaming Optimizations


GCC Optimizations


Glibc Optimizations & IFUNC


Phase 4 - Distro Adoption



A man builds a fine house; and now he has a master, and a task for life; he is to furnish,

watch, show it, and keep it in repair, the rest of his days

- Ralph Waldo Emerson

Thank You#LAS16

For further information: www.linaro.orgLAS16 keynotes and videos on: connect.linaro.org

LAS16-106: GNU Toolchain Development Lifecycle

Technology