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73a8b950cb
* reworked ID handling * the packed AST now has its own ID mechanism * basic serialization code works * extract rodfiles to its own module * rodfiles: store and compare configs * rodfiles: store dependencies * store config at the end * precise dependency tracking * dependency tracking for rodfiles * completed loading of PSym, PType, etc * removed dead code * bugfix: do not realloc seqs when taking addr into an element * make IC opt-in for now * makes tcompilerapi green again * final cleanups Co-authored-by: Andy Davidoff <github@andy.disruptek.com>
42 lines
1.5 KiB
ReStructuredText
42 lines
1.5 KiB
ReStructuredText
====================================
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Incremental Recompilations
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====================================
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We split the Nim compiler into a frontend and a backend.
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The frontend produces a set of `.rod` files. Every `.nim` module
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produces its own `.rod` file.
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- The IR must be a faithful representation of the AST in memory.
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- The backend can do its own caching but doesn't have to.
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- We know by comparing 'nim check compiler/nim' against 'nim c compiler/nim'
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that 2/3 of the compiler's runtime is spent in the frontend. Hence we
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implement IC for the frontend first and only later for the backend. The
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backend will recompile everything until we implement its own caching
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mechanisms.
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Advantage of the "set of files" vs the previous global database:
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- By construction, we either read from the `.rod` file or from the
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`.nim` file, there can be no inconsistency. There can also be no
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partial updates.
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- No dependency to external packages (SQLite). SQLite simply is too
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slow and the old way of serialization was too slow too. We use a
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format designed for Nim and expect to base further tools on this
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file format.
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References to external modules must be (moduleId, symId) pairs.
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The symbol IDs are module specific. This way no global ID increment
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mechanism needs to be implemented that we could get wrong. ModuleIds
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are rod-file specific too.
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Global state
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------------
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Global persistent state will be kept in a project specific `.rod` file.
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Rod File Format
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---------------
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It's a simple binary file format. `rodfiles.nim` contains some details.
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