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f348b8ed6d
This improves integration with other projects. Like for example Guile already has files named jit.c and jit.h; it's easier to manage if lightening uses its own file names.
37 lines
1.5 KiB
Markdown
37 lines
1.5 KiB
Markdown
# Lightening
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Lightening is a just-in-time code generation library derived from GNU
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Lightning, adapted to the purposes of the GNU Guile project.
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## Use
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```
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gcc -flto -O2 -g -o lightening.o -c lightening/lightening.c
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gcc -flto -O2 -g -o my-program lightening.o my-program.c
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```
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See the GNU Lightning manual for more on how to program against
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Lightening (much of the details are the same).
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## What's the difference with GNU Lightning?
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This project is called Lightening because it's lighter-weight than GNU
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Lightning. When you go to generate code at run-time with GNU Lightning,
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what happens is that you build up a graph of nodes which GNU Lightning
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"optimizes" before finally emitting machine code. These optimizations
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can improve register allocation around call sites. However they are not
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helpful from a Guile perspective, as they get in the way of register
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allocation that we need to do; and they actually prevent access to all
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the registers that we would like to have.
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Guile needs a simple, light-weight code generation library. The GNU
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Lightning architecture-specific backends provide the bulk of this
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functionality, and Lightening wraps it all in a lightweight API.
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## Status
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Only the x86-64 port is currently usable. I plan to re-enable 32-bit
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x86 shortly, and then work on 32-bit and 64-bit ARM. Other
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architectures may come with time, but help is very much appreciated
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there. The test suite is still in progress but will be fairly
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comprehensive in terms of API surface.
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