gcc/jit/notes.txt

   1 Client Code   . Generated .            libgccjit.so
   2               . code      .
   3               .           . JIT API  . JIT "Frontend". (libbackend.a)
   4 ....................................................................................
   5    │          .           .          .               .
   6     ──────────────────────────>      .               .
   7               .           .    │     .               .
   8               .           .    V     .               .
   9               .           .    ──> libgccjit.c       .
  10               .           .        │ (error-checking).
  11               .           .        │                 .
  12               .           .        ──> jit-recording.c
  13               .           .              (record API calls)
  14               .           .    <───────              .
  15               .           .    │     .               .
  16    <───────────────────────────      .               .
  17    │          .           .          .               .
  18    │          .           .          .               .
  19    V          .           .  gcc_jit_context_compile .
  20     ──────────────────────────>      .               .
  21               .           .    │ start of recording::context::compile ()
  22               .           .    │     .               .
  23               .           .    │ start of playback::context::compile ()
  24               .           .    │   (create tempdir)  .
  25               .           .    │     .               .
  26               .           .    │ ACQUIRE MUTEX       .
  27               .           .    │     .               .
  28               .           .    V───────────────────────> toplev::main (for now)
  29               .           .          .               .       │
  30               .           .          .               .   (various code)
  31               .           .          .               .       │
  32               .           .          .               .       V
  33               .           .          .    <───────────────── langhook:parse_file
  34               .           .          .    │          .
  35               .           .          .    │ (jit_langhook_parse_file)
  36               .           .          .    │          .
  37 ..........................................│..................VVVVVVVVVVVVV...
  38               .           .          .    │          .       No GC in here
  39               .           .          .    │ jit-playback.c
  40               .           .          .    │   (playback of API calls)
  41               .           .          .    ───────────────> creation of functions,
  42               .           .          .               .     types, expression trees
  43               .           .          .    <──────────────── etc
  44               .           .          .    │(handle_locations: add locations to
  45               .           .          .    │ linemap and associate them with trees)
  46               .           .          .    │          .
  47               .           .          .    │          .       No GC in here
  48 ..........................................│..................AAAAAAAAAAAAA...
  49               .           .          .    │ for each function
  50               .           .          .    ──> postprocess
  51               .           .          .        │      .
  52               .           .          .        ────────────> cgraph_finalize_function
  53               .           .          .        <────────────
  54               .           .          .     <──       .
  55               .           .          .    │          .
  56               .           .          .    ──────────────────> (end of
  57               .           .          .               .       │ langhook_parse_file)
  58               .           .          .               .       │
  59               .           .          .               .   (various code)
  60               .           .          .               .       │
  61               .           .          .               .       ↓
  62               .           .          .    <───────────────── langhook:write_globals
  63               .           .          .    │          .
  64               .           .          .    │ (jit_langhook_write_globals)
  65               .           .          .    │          .
  66               .           .          .    │          .
  67               .           .          .    ──────────────────> finalize_compilation_unit
  68               .           .          .               .       │
  69               .           .          .               .   (the middle─end and backend)
  70               .           .          .               .       ↓
  71               .           .    <───────────────────────────── end of toplev::main
  72               .           .    │     .               .
  73               .           .    V───────────────────────> toplev::finalize
  74               .           .          .               . │   (purge internal state)
  75               .           .    <──────────────────────── end of toplev::finalize
  76               .           .    │     .               .
  77               .           .    V─> playback::context::postprocess:
  78               .           .      │   .               .
  79               .           .      │   (assuming an in-memory compile):
  80               .           .      │   .               .
  81               .           .      --> Convert assembler to DSO, via embedded
  82               .           .          copy of driver:
  83               .           .           driver::main ()
  84               .           .             invocation of "as"
  85               .           .             invocation of "ld"
  86               .           .           driver::finalize ()
  87               .           .      <----
  88               .           .      │   .               .
  89               .           .      │   . Load DSO (dlopen "fake.so")
  90               .           .      │   .               .
  91               .           .      │   . Bundle it up in a jit::result
  92               .           .    <──   .               .
  93               .           .    │     .               .
  94               .           .    │ RELEASE MUTEX       .
  95               .           .    │     .               .
  96               .           .    │ end of playback::context::compile ()
  97               .           .    │     .               .
  98               .           .    │ playback::context dtor
  99               .           .     ──>  .               .
 100               .           .       │ Normally we cleanup the tempdir here:
 101               .           .       │   ("fake.so" is unlinked from the
 102               .           .       │    filesystem at this point)
 103               .           .       │ If the client code requested debuginfo, the
 104               .           .       │ cleanup happens later (in gcc_jit_result_release)
 105               .           .       │ to make it easier on the debugger (see PR jit/64206)
 106               .           .    <──   .               .
 107               .           .    │     .               .
 108               .           .    │ end of recording::context::compile ()
 109    <───────────────────────────      .               .
 110    │          .           .          .               .
 111    V          .           .  gcc_jit_result_get_code .
 112     ──────────────────────────>      .               .
 113               .           .    │ dlsym () within loaded DSO
 114    <───────────────────────────      .               .
 115    Get (void*).           .          .               .
 116    │          .           .          .               .
 117    │ Call it  .           .          .               .
 118    ───────────────>       .          .               .
 119               .    │      .          .               .
 120               .    │      .          .               .
 121    <───────────────       .          .               .
 122    │          .           .          .               .
 123 etc│          .           .          .               .
 124    │          .           .          .               .
 125    V          .           .  gcc_jit_result_release  .
 126     ──────────────────────────>      .               .
 127               .           .    │ dlclose () the loaded DSO
 128               .           .    │    (code becomes uncallable)
 129               .           .    │     .               .
 130               .           .    │ If the client code requested debuginfo, then
 131               .           .    │ cleanup of the tempdir was delayed.
 132               .           .    │ If that was the case, clean it up now.
 133    <───────────────────────────      .               .
 134    │          .           .          .               .