mlton/ssa/prepasses.sig

   1 (* Copyright (C) 2005-2007 Henry Cejtin, Matthew Fluet, Suresh
   2  *    Jagannathan, and Stephen Weeks.
   3  *
   4  * MLton is released under a BSD-style license.
   5  * See the file MLton-LICENSE for details.
   6  *)
   7
   8 signature PREPASSES_STRUCTS =
   9    sig
  10       include TYPE_CHECK
  11    end
  12
  13 signature PREPASSES =
  14    sig
  15       include PREPASSES_STRUCTS
  16
  17       (* A critical edge is one that connects a block with two or more
  18        * succesors to one with two or more predecessors.
  19        * This prepass breaks all critical edges by inserting an eta-block.
  20        * For some analyses and transformations, simply ensuring the unique
  21        * successor or predecessor property is sufficient.  (For example, see
  22        * the comments at the end of "Conditional Constant Propagation" in
  23        * Section 19.3 of Appel's "Modern Compiler Implementation in ML".)
  24        * However, passes that require critical edges to be broken in order
  25        * to accomodate code motion (for example, PRE), should also break an
  26        * edge that connects a block with non-functional control transfer to
  27        * one with two or more predecessors.
  28        *)
  29       val breakCriticalEdgesFunction:
  30          Function.t * {codeMotion: bool} -> Function.t
  31       val breakCriticalEdges:
  32          Program.t * {codeMotion: bool} -> Program.t
  33       val eliminateDeadBlocksFunction: Function.t -> Function.t
  34       val eliminateDeadBlocks: Program.t -> Program.t
  35       val orderFunctions: Program.t -> Program.t
  36       val reverseFunctions: Program.t -> Program.t
  37    end