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Diffstat (limited to 'compiler/ic/design.rst')
| -rw-r--r-- | compiler/ic/design.rst | 40 |
1 files changed, 27 insertions, 13 deletions
diff --git a/compiler/ic/design.rst b/compiler/ic/design.rst index 1a33f6a27..b096e3103 100644 --- a/compiler/ic/design.rst +++ b/compiler/ic/design.rst @@ -7,12 +7,8 @@ The frontend produces a set of `.rod` files. Every `.nim` module produces its own `.rod` file. - The IR must be a faithful representation of the AST in memory. -- The backend can do its own caching but doesn't have to. -- We know by comparing 'nim check compiler/nim' against 'nim c compiler/nim' - that 2/3 of the compiler's runtime is spent in the frontend. Hence we - implement IC for the frontend first and only later for the backend. The - backend will recompile everything until we implement its own caching - mechanisms. +- The backend can do its own caching but doesn't have to. In the + current implementation the backend also caches its results. Advantage of the "set of files" vs the previous global database: - By construction, we either read from the `.rod` file or from the @@ -29,14 +25,32 @@ mechanism needs to be implemented that we could get wrong. ModuleIds are rod-file specific too. -Configuration setup changes ---------------------------- - -For a MVP these are not detected. Later the configuration will be -stored in every `.rod` file. - Global state ------------ -Global persistent state will be kept in a project specific `.rod` file. +There is no global state. + +Rod File Format +--------------- + +It's a simple binary file format. `rodfiles.nim` contains some details. + + +Backend +------- + +Nim programmers have to come to enjoy whole-program dead code elimination, +by default. Since this is a "whole program" optimization, it does break +modularity. However, thanks to the packed AST representation we can perform +this global analysis without having to unpack anything. This is basically +a mark&sweep GC algorithm: + +- Start with the top level statements. Every symbol that is referenced + from a top level statement is not "dead" and needs to be compiled by + the backend. +- Every symbol referenced from a referenced symbol also has to be + compiled. + +Caching logic: Only if the set of alive symbols is different from the +last run, the module has to be regenerated. |