doc/guide/src/DeadCode.adoc

   1 DeadCode
   2 ========
   3
   4 <:DeadCode:> is an optimization pass for the <:CoreML:>
   5 <:IntermediateLanguage:>, invoked from <:CoreMLSimplify:>.
   6
   7 == Description ==
   8
   9 This pass eliminates declarations from the
  10 <:BasisLibrary:Basis Library> not needed by the user program.
  11
  12 == Implementation ==
  13
  14 * <!ViewGitFile(mlton,master,mlton/core-ml/dead-code.sig)>
  15 * <!ViewGitFile(mlton,master,mlton/core-ml/dead-code.fun)>
  16
  17 == Details and Notes ==
  18
  19 In order to compile small programs rapidly, a pass of dead code
  20 elimination is run in order to eliminate as much of the Basis Library
  21 as possible.  The dead code elimination algorithm used is not safe in
  22 general, and only works because the Basis Library implementation has
  23 special properties:
  24
  25 * it terminates
  26 * it performs no I/O
  27
  28 The dead code elimination includes the minimal set of
  29 declarations from the Basis Library so that there are no free
  30 variables in the user program (or remaining Basis Library
  31 implementation).  It has a special hack to include all
  32 bindings of the form:
  33 [source,sml]
  34 ----
  35  val _ = ...
  36 ----
  37
  38 There is an <:MLBasisAnnotations:ML Basis annotation>,
  39 `deadCode true`, that governs which code is subject to this unsafe
  40 dead-code elimination.