Change the graph structure to contain the code generator object for

embedded code objects (e.g. functions) rather than the generated code
object.  This change means that the compiler generates code for
everything at the end, rather then generating code for each function
as it finds it.  Implementation note: _convert_LOAD_CONST in
pyassem.py must be change to call getCode().

Other changes follow.  Several changes creates extra edges between
basic blocks to reflect control flow for loops and exceptions.  These
missing edges had gone unnoticed because they do not affect the
current compilation process.

pyassem.py:
    Add _enable_debug() and _disable_debug() methods that print
    instructions and blocks to stdout as they are generated.

    Add edges between blocks for instructions like SETUP_LOOP,
    FOR_LOOP, etc.

    Add pruneNext to get rid of bogus edges remaining after
    unconditional transfer ops (e.g. JUMP_FORWARD)

    Change repr of Block to omit block length.

pycodegen.py:
    Make sure a new block is started after FOR_LOOP, etc.

    Change assert implementation to use RAISE_VARARGS 1 when there is
    no user-specified failure output.

misc.py:
    Implement __contains__ and copy for Set.

3 files changed, 133 insertions, 21 deletions

diff --git a/Lib/compiler/misc.py b/Lib/compiler/misc.py
index e57acae78c..29ff866780 100644
--- a/Lib/compiler/misc.py
+++ b/Lib/compiler/misc.py
@@ -14,6 +14,8 @@ class Set:
         self.elts = {}
     def __len__(self):
         return len(self.elts)
+    def __contains__(self, elt):
+        return self.elts.has_key(elt)
     def add(self, elt):
         self.elts[elt] = elt
     def elements(self):
@@ -22,6 +24,10 @@ class Set:
         return self.elts.has_key(elt)
     def remove(self, elt):
         del self.elts[elt]
+    def copy(self):
+        c = Set()
+        c.elts.update(self.elts)
+        return c
 
 class Stack:
     def __init__(self):
diff --git a/Lib/compiler/pyassem.py b/Lib/compiler/pyassem.py
index dcc8bc08fa..0b6701ef9f 100644
--- a/Lib/compiler/pyassem.py
+++ b/Lib/compiler/pyassem.py
@@ -3,10 +3,18 @@
 import dis
 import new
 import string
+import sys
 import types
 
 from compiler import misc
 
+def xxx_sort(l):
+    l = l[:]
+    def sorter(a, b):
+        return cmp(a.bid, b.bid)
+    l.sort(sorter)
+    return l
+
 class FlowGraph:
     def __init__(self):
         self.current = self.entry = Block()
@@ -16,13 +24,18 @@ class FlowGraph:
         self.blocks.add(self.exit)
 
     def startBlock(self, block):
+        if self._debug:
+            if self.current:
+                print "end", repr(self.current)
+                print "   ", self.current.get_children()
+            print repr(block)
         self.current = block
 
-    def nextBlock(self, block=None):
-        if block is None:
-            block = self.newBlock()
+    def nextBlock(self, block=None, force=0):
         # XXX think we need to specify when there is implicit transfer
-        # from one block to the next
+        # from one block to the next.  might be better to represent this
+        # with explicit JUMP_ABSOLUTE instructions that are optimized
+        # out when they are unnecessary.
         #
         # I think this strategy works: each block has a child
         # designated as "next" which is returned as the last of the
@@ -30,6 +43,16 @@ class FlowGraph:
         # reverse post order, the "next" block will always be emitted
         # immediately after its parent.
         # Worry: maintaining this invariant could be tricky
+        if block is None:
+            block = self.newBlock()
+
+        # Note: If the current block ends with an unconditional
+        # control transfer, then it is incorrect to add an implicit
+        # transfer to the block graph.  The current code requires
+        # these edges to get the blocks emitted in the right order,
+        # however. :-(  If a client needs to remove these edges, call
+        # pruneEdges().
+        
         self.current.addNext(block)
         self.startBlock(block)
 
@@ -41,13 +64,24 @@ class FlowGraph:
     def startExitBlock(self):
         self.startBlock(self.exit)
 
+    _debug = 0
+
+    def _enable_debug(self):
+        self._debug = 1
+
+    def _disable_debug(self):
+        self._debug = 0
+
     def emit(self, *inst):
-        # XXX should jump instructions implicitly call nextBlock?
+        if self._debug:
+            print "\t", inst
         if inst[0] == 'RETURN_VALUE':
             self.current.addOutEdge(self.exit)
+        if len(inst) == 2 and isinstance(inst[1], Block):
+            self.current.addOutEdge(inst[1])
         self.current.emit(inst)
 
-    def getBlocks(self):
+    def getBlocksInOrder(self):
         """Return the blocks in reverse postorder
 
         i.e. each node appears before all of its successors
@@ -64,13 +98,57 @@ class FlowGraph:
         # hack alert
         if not self.exit in order:
             order.append(self.exit)
+
+##        for b in order:
+##            print repr(b)
+##            print "\t", b.get_children()
+##            print b
+##            print
+            
         return order
 
+    def getBlocks(self):
+        return self.blocks.elements()
+
+    def getRoot(self):
+        """Return nodes appropriate for use with dominator"""
+        return self.entry
+    
+    def getContainedGraphs(self):
+        l = []
+        for b in self.getBlocks():
+            l.extend(b.getContainedGraphs())
+        return l
+
+    _uncond_transfer = ('RETURN_VALUE', 'RAISE_VARARGS',
+                        'JUMP_ABSOLUTE', 'JUMP_FORWARD')
+
+    def pruneNext(self):
+        """Remove bogus edge for unconditional transfers
+
+        Each block has a next edge that accounts for implicit control
+        transfers, e.g. from a JUMP_IF_FALSE to the block that will be
+        executed if the test is true.
+
+        These edges must remain for the current assembler code to
+        work. If they are removed, the dfs_postorder gets things in
+        weird orders.  However, they shouldn't be there for other
+        purposes, e.g. conversion to SSA form.  This method will
+        remove the next edge when it follows an unconditional control
+        transfer.
+        """
+        try:
+            op, arg = self.insts[-1]
+        except (IndexError, TypeError):
+            return
+        if op in self._uncond_transfer:
+            self.next = []
+
 def dfs_postorder(b, seen):
     """Depth-first search of tree rooted at b, return in postorder"""
     order = []
     seen[b] = b
-    for c in b.children():
+    for c in b.get_children():
         if seen.has_key(c):
             continue
         order = order + dfs_postorder(c, seen)
@@ -91,10 +169,9 @@ class Block:
 
     def __repr__(self):
         if self.label:
-            return "<block %s id=%d len=%d>" % (self.label, self.bid,
-                                                len(self.insts)) 
+            return "<block %s id=%d>" % (self.label, self.bid)
         else:
-            return "<block id=%d len=%d>" % (self.bid, len(self.insts))
+            return "<block id=%d>" % (self.bid)
 
     def __str__(self):
         insts = map(str, self.insts)
@@ -120,9 +197,26 @@ class Block:
         self.next.append(block)
         assert len(self.next) == 1, map(str, self.next)
 
-    def children(self):
+    def get_children(self):
+        if self.next and self.next[0] in self.outEdges:
+            self.outEdges.remove(self.next[0])
         return self.outEdges.elements() + self.next
 
+    def getContainedGraphs(self):
+        """Return all graphs contained within this block.
+
+        For example, a MAKE_FUNCTION block will contain a reference to
+        the graph for the function body.
+        """
+        contained = []
+        for inst in self.insts:
+            if len(inst) == 1:
+                continue
+            op = inst[1]
+            if hasattr(op, 'graph'):
+                contained.append(op.graph)
+        return contained
+
 # flags for code objects
 CO_OPTIMIZED = 0x0001
 CO_NEWLOCALS = 0x0002
@@ -204,7 +298,7 @@ class PyFlowGraph(FlowGraph):
         pc = 0
         begin = {}
         end = {}
-        for b in self.getBlocks():
+        for b in self.getBlocksInOrder():
             begin[b] = pc
             for inst in b.getInstructions():
                 insts.append(inst)
@@ -274,6 +368,8 @@ class PyFlowGraph(FlowGraph):
 
     _converters = {}
     def _convert_LOAD_CONST(self, arg):
+        if hasattr(arg, 'getCode'):
+            arg = arg.getCode()
         return self._lookupName(arg, self.consts)
 
     def _convert_LOAD_FAST(self, arg):
diff --git a/Lib/compiler/pycodegen.py b/Lib/compiler/pycodegen.py
index bf54c3203e..a1b5d1db1a 100644
--- a/Lib/compiler/pycodegen.py
+++ b/Lib/compiler/pycodegen.py
@@ -160,7 +160,7 @@ class CodeGenerator:
         self.set_lineno(node)
         for default in node.defaults:
             self.visit(default)
-        self.emit('LOAD_CONST', gen.getCode())
+        self.emit('LOAD_CONST', gen)
         self.emit('MAKE_FUNCTION', len(node.defaults))
 
     def visitClass(self, node):
@@ -195,7 +195,7 @@ class CodeGenerator:
             self.emit('POP_TOP')
             self.visit(suite)
             self.emit('JUMP_FORWARD', end)
-            self.nextBlock(nextTest)
+            self.startBlock(nextTest)
             self.emit('POP_TOP')
         if node.else_:
             self.visit(node.else_)
@@ -243,10 +243,11 @@ class CodeGenerator:
         self.nextBlock(start)
         self.set_lineno(node)
         self.emit('FOR_LOOP', anchor)
+        self.nextBlock()
         self.visit(node.assign)
         self.visit(node.body)
         self.emit('JUMP_ABSOLUTE', start)
-        self.nextBlock(anchor)
+        self.startBlock(anchor)
         self.emit('POP_BLOCK')
         if node.else_:
             self.visit(node.else_)
@@ -304,7 +305,7 @@ class CodeGenerator:
         if len(node.ops) > 1:
             end = self.newBlock()
             self.emit('JUMP_FORWARD', end)
-            self.nextBlock(cleanup)
+            self.startBlock(cleanup)
             self.emit('ROT_TWO')
             self.emit('POP_TOP')
             self.nextBlock(end)
@@ -344,11 +345,11 @@ class CodeGenerator:
             if cont:
                 skip_one = self.newBlock()
                 self.emit('JUMP_FORWARD', skip_one)
-                self.nextBlock(cont)
+                self.startBlock(cont)
                 self.emit('POP_TOP')
                 self.nextBlock(skip_one)
             self.emit('JUMP_ABSOLUTE', start)
-            self.nextBlock(anchor)
+            self.startBlock(anchor)
         self.delName(append)
         
         self.__list_count = self.__list_count - 1
@@ -363,6 +364,7 @@ class CodeGenerator:
         self.emit('SET_LINENO', node.lineno)
         self.nextBlock(start)
         self.emit('FOR_LOOP', anchor)
+        self.nextBlock()
         self.visit(node.assign)
         return start, anchor
 
@@ -390,9 +392,13 @@ class CodeGenerator:
         self.visit(node.test)
         self.emit('JUMP_IF_TRUE', end)
         self.nextBlock()
+        self.emit('POP_TOP')
         self.emit('LOAD_GLOBAL', 'AssertionError')
-        self.visit(node.fail)
-        self.emit('RAISE_VARARGS', 2)
+        if node.fail:
+            self.visit(node.fail)
+            self.emit('RAISE_VARARGS', 2)
+        else:
+            self.emit('RAISE_VARARGS', 1)
         self.nextBlock(end)
         self.emit('POP_TOP')
 
@@ -419,10 +425,11 @@ class CodeGenerator:
             lElse = end
         self.set_lineno(node)
         self.emit('SETUP_EXCEPT', handlers)
+        self.nextBlock()
         self.visit(node.body)
         self.emit('POP_BLOCK')
         self.emit('JUMP_FORWARD', lElse)
-        self.nextBlock(handlers)
+        self.startBlock(handlers)
         
         last = len(node.handlers) - 1
         for i in range(len(node.handlers)):
@@ -446,6 +453,8 @@ class CodeGenerator:
             self.emit('JUMP_FORWARD', end)
             if expr:
                 self.nextBlock(next)
+            else:
+                self.nextBlock()
             self.emit('POP_TOP')
         self.emit('END_FINALLY')
         if node.else_:
@@ -457,6 +466,7 @@ class CodeGenerator:
         final = self.newBlock()
         self.set_lineno(node)
         self.emit('SETUP_FINALLY', final)
+        self.nextBlock()
         self.visit(node.body)
         self.emit('POP_BLOCK')
         self.emit('LOAD_CONST', None)