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diff --git a/rod/passes.nim b/rod/passes.nim
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+#
+#
+#           The Nimrod Compiler
+#        (c) Copyright 2009 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+# This module implements the passes functionality. A pass must implement the
+# `TPass` interface.
+
+import 
+  strutils, lists, options, ast, astalgo, llstream, msgs, platform, os, 
+  condsyms, idents, rnimsyn, types, extccomp, math, magicsys, nversion, nimsets, 
+  syntaxes, times, rodread
+
+type 
+  TPassContext* = object of TObject # the pass's context
+  PPassContext* = ref TPassContext
+  TPass* = tuple[open: proc (module: PSym, filename: string): PPassContext, 
+      openCached: proc (module: PSym, filename: string, rd: PRodReader): PPassContext, 
+                 close: proc (p: PPassContext, n: PNode): PNode, 
+                 process: proc (p: PPassContext, topLevelStmt: PNode): PNode] # a 
+                                                                              # pass is a 
+                                                                              # tuple of 
+                                                                              # procedure 
+                                                                              # vars
+                                                                              # 
+                                                                              # ``TPass.close`` 
+                                                                              # may 
+                                                                              # produce 
+                                                                              # additional 
+                                                                              # nodes. 
+                                                                              # These 
+                                                                              # are 
+                                                                              # passed to 
+                                                                              # the 
+                                                                              # other
+                                                                              # 
+                                                                              # close 
+                                                                              # procedures. 
+                                                                              # This 
+                                                                              # mechanism is 
+                                                                              # needed 
+                                                                              # for 
+                                                                              # the 
+                                                                              # instantiation of
+                                                                              # 
+                                                                              # generics.
+
+proc registerPass*(p: TPass)
+proc initPass*(p: var TPass)
+  # This implements a memory preserving scheme: Top level statements are
+  # processed in a pipeline. The compiler never looks at a whole module
+  # any longer. However, this is simple to change, as new passes may perform
+  # whole program optimizations. For now, we avoid it to save a lot of memory.
+proc processModule*(module: PSym, filename: string, stream: PLLStream, 
+                    rd: PRodReader)
+proc astNeeded*(s: PSym): bool
+  # The ``rodwrite`` module uses this to determine if the body of a proc
+  # needs to be stored. The passes manager frees s.sons[codePos] when
+  # appropriate to free the procedure body's memory. This is important
+  # to keep memory usage down.
+  # the semantic checker needs these:
+var 
+  gImportModule*: proc (filename: string): PSym
+  gIncludeFile*: proc (filename: string): PNode
+
+# implementation
+
+proc astNeeded(s: PSym): bool = 
+  if (s.kind in {skMethod, skProc}) and
+      ({sfCompilerProc, sfCompileTime} * s.flags == {}) and
+      (s.typ.callConv != ccInline) and (s.ast.sons[genericParamsPos] == nil): 
+    result = false
+  else: 
+    result = true
+  
+const 
+  maxPasses = 10
+
+type 
+  TPassContextArray = array[0..maxPasses - 1, PPassContext]
+
+var 
+  gPasses: array[0..maxPasses - 1, TPass]
+  gPassesLen: int
+
+proc registerPass(p: TPass) = 
+  gPasses[gPassesLen] = p
+  inc(gPassesLen)
+
+proc openPasses(a: var TPassContextArray, module: PSym, filename: string) = 
+  for i in countup(0, gPassesLen - 1): 
+    if not isNil(gPasses[i].open): a[i] = gPasses[i].open(module, filename)
+    else: a[i] = nil
+  
+proc openPassesCached(a: var TPassContextArray, module: PSym, filename: string, 
+                      rd: PRodReader) = 
+  for i in countup(0, gPassesLen - 1): 
+    if not isNil(gPasses[i].openCached): 
+      a[i] = gPasses[i].openCached(module, filename, rd)
+    else: 
+      a[i] = nil
+  
+proc closePasses(a: var TPassContextArray) = 
+  var m: PNode
+  m = nil
+  for i in countup(0, gPassesLen - 1): 
+    if not isNil(gPasses[i].close): m = gPasses[i].close(a[i], m)
+    a[i] = nil                # free the memory here
+  
+proc processTopLevelStmt(n: PNode, a: var TPassContextArray) = 
+  var m: PNode
+  # this implements the code transformation pipeline
+  m = n
+  for i in countup(0, gPassesLen - 1): 
+    if not isNil(gPasses[i].process): m = gPasses[i].process(a[i], m)
+  
+proc processTopLevelStmtCached(n: PNode, a: var TPassContextArray) = 
+  var m: PNode
+  # this implements the code transformation pipeline
+  m = n
+  for i in countup(0, gPassesLen - 1): 
+    if not isNil(gPasses[i].openCached): m = gPasses[i].process(a[i], m)
+  
+proc closePassesCached(a: var TPassContextArray) = 
+  var m: PNode
+  m = nil
+  for i in countup(0, gPassesLen - 1): 
+    if not isNil(gPasses[i].openCached) and not isNil(gPasses[i].close): 
+      m = gPasses[i].close(a[i], m)
+    a[i] = nil                # free the memory here
+  
+proc processModule(module: PSym, filename: string, stream: PLLStream, 
+                   rd: PRodReader) = 
+  var 
+    p: TParsers
+    n: PNode
+    a: TPassContextArray
+    s: PLLStream
+  if rd == nil: 
+    openPasses(a, module, filename)
+    if stream == nil: 
+      s = LLStreamOpen(filename, fmRead)
+      if s == nil: 
+        rawMessage(errCannotOpenFile, filename)
+        return 
+    else: 
+      s = stream
+    while true: 
+      openParsers(p, filename, s)
+      while true: 
+        n = parseTopLevelStmt(p)
+        if n == nil: break 
+        processTopLevelStmt(n, a)
+      closeParsers(p)
+      if s.kind != llsStdIn: break 
+    closePasses(a)            # id synchronization point for more consistent code generation:
+    IDsynchronizationPoint(1000)
+  else: 
+    openPassesCached(a, module, filename, rd)
+    n = loadInitSection(rd)   #MessageOut('init section' + renderTree(n));
+    for i in countup(0, sonsLen(n) - 1): processTopLevelStmtCached(n.sons[i], a)
+    closePassesCached(a)
+
+proc initPass(p: var TPass) = 
+  p.open = nil
+  p.openCached = nil
+  p.close = nil
+  p.process = nil