Commits on May 25, 2023

1. tools: speedup compilation of js2c output …

   Incremental compilation of Node.js is slow. Currently on a powerful
   Linux machine, it takes about 9 seconds and 830 MB of memory to compile
   `gen/node_javascript.cc` with g++. This is the longest step when
   recompiling a small change to a Javascript file.
   
   `gen/node_javascript.cc` contains a lot of large binary literals of our
   Javascript source code. It is well-known that embedding large binary
   literals as C/C++ arrays is slow. One workaround is to include the data
   as string literals instead. This is particularly nice for the Javascript
   included via js2c, which look better as string literals anyway.
   
   Add a build flag `NODE_JS2C_USE_STRING_LITERALS` to js2c. When this flag
   is set, we emit string literals instead of array literals, i.e.:
   
   ```c++
   // old: static const uint8_t X[] = { ... };
   static const uint8_t *X = R"JS2C1b732aee(...)JS2C1b732aee";
   
   // old: static const uint16_t Y[] = { ... };
   static const uint16_t *Y = uR"JS2C1b732aee(...)JS2C1b732aee";
   ```
   
   This requires some modest refactoring in order to deal with the flag
   being on or off, but the new code itself is actually shorter.
   
   I only enabled the new flag on Linux/macOS, since those are systems that
   I have available for testing. On my Linux system with gcc, it speeds up
   compilation by 5.5s (9.0s -> 3.5s). On my Mac system with clang, it
   speeds up compilation by 2.2s (3.7s -> 1.5s). (I don't think this flag
   will work with MSVC, but it'd probably speed up clang on windows.)
   
   The long-term goal here is probably to allow this to occur incrementally
   per Javascript file & in parallel, to avoid recompiling all of
   `gen/node_javascript.cc`. Unfortunately the necessary gyp incantations
   seem impossible (or at least, far beyond me). Anyway, a 60% speedup is a
   nice enough win.
   
   Refs: nodejs#47984

   

   kvakil committed May 25, 2023
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