[SAoC] "Druntime for Microcontrollers" project thread
feklushkin.denis at gmail.com
Mon Sep 14 09:11:07 UTC 2020
Hi! I am also very interested in this.
This is my unfinished work about porting D to ARM Cortex-M MCU:
Below in the comments I briefly write some thoughts that I came
by doing this work. Maybe it will be helpful.
On Monday, 14 September 2020 at 07:59:08 UTC, Severin Teona wrote:
> A big problem I encountered while porting the userland was the
> fact that the Druntime was not built for the target
> architecture and even if it would have been, it would not have
> fit the memory on the device.
Link Time Optimization (LTO) is available in LLVM-based ldc2 and
can dramatically (2-3 times!) decrease .text size.
> Starting from this point, I have decided to participate this
> year at Symmetry Autumn of Code and create a micro-runtime for
> the D language, to be used with microcontrollers and memory
> constrained devices.
Thought about this while working on my project and came to
conclusion that it makes no sense to write a new druntime. There
is nothing superfluous in the existing "regular" druntime, any
part of it is needed for key concepts of D.
> During SAoC, I have planned the next steps:
> Milestone 1: Build a runtime (doesn’t matter the size yet) for
> the specified architecture:
> - Try to build the runtime for the Cortex-M CPU architecture:
> * either by using the ‘ldc-build-runtime’ toolchain (which
> currently fails because of a ‘CMake’ error)
> * or by building and compiling manually the source code
> - If the build succeeds, I won’t be able to test it because the
> size of the druntime doesn’t fit in the microcontroller’s
> constrained resources.
QEMU have -m option to add slightly more memory into emulated
Cortex M3 devices - can be useful to fit all druntime tests.
> - Begin removing unnecessary functionalities (that a code
> running on a microcontroller does not need) from the ‘object.d’
> file (most probably by stubbing the code)
> Milestone 2: Try to have a small object.d implementation
> - Continue removing any functionality a small class doesn’t
> - Try to test the new ‘object.d’ on the microcontroller after a
> successful build of the file.
> Milestone 3: Attempt a port of the current Garbage Collector
> - Try to port the current GC for the target architecture
> - If that fails in the first 2 weeks, try to implement a
> small-sized GC from scratch (this could exceed the deadline of
> this milestone)
As I remember, current default Garbage Collector just works - it
is not need any porting.
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