pyassem.py:
Fix annoying bugs in flow graph layout code. In some cases the
implicit control transfers weren't honored. In other cases,
JUMP_FORWARD instructions jumped backwards.
Remove unused arg from nextBlock().
pycodegen.py
Add optional force kwarg to set_lineno() that will emit a
SET_LINENO even if it is the same as the previous lineno.
Use explicit LOAD_FAST and STORE_FAST to access list comp implicit
variables. (The symbol table doesn't know about them.)
diff --git a/Lib/compiler/pyassem.py b/Lib/compiler/pyassem.py
index 15e91f4..e8810ae 100644
--- a/Lib/compiler/pyassem.py
+++ b/Lib/compiler/pyassem.py
@@ -27,11 +27,12 @@
if self._debug:
if self.current:
print "end", repr(self.current)
+ print " next", self.current.next
print " ", self.current.get_children()
print repr(block)
self.current = block
- def nextBlock(self, block=None, force=0):
+ def nextBlock(self, block=None):
# XXX think we need to specify when there is implicit transfer
# from one block to the next. might be better to represent this
# with explicit JUMP_ABSOLUTE instructions that are optimized
@@ -95,12 +96,110 @@
b.addNext(self.exit)
order = dfs_postorder(self.entry, {})
order.reverse()
+ self.fixupOrder(order, self.exit)
# hack alert
if not self.exit in order:
order.append(self.exit)
return order
+ def fixupOrder(self, blocks, default_next):
+ """Fixup bad order introduced by DFS."""
+
+ # XXX This is a total mess. There must be a better way to get
+ # the code blocks in the right order.
+
+ self.fixupOrderHonorNext(blocks, default_next)
+ self.fixupOrderForward(blocks, default_next)
+
+ def fixupOrderHonorNext(self, blocks, default_next):
+ """Fix one problem with DFS.
+
+ The DFS uses child block, but doesn't know about the special
+ "next" block. As a result, the DFS can order blocks so that a
+ block isn't next to the right block for implicit control
+ transfers.
+ """
+ index = {}
+ for i in range(len(blocks)):
+ index[blocks[i]] = i
+
+ for i in range(0, len(blocks) - 1):
+ b = blocks[i]
+ n = blocks[i + 1]
+ if not b.next or b.next[0] == default_next or b.next[0] == n:
+ continue
+ # The blocks are in the wrong order. Find the chain of
+ # blocks to insert where they belong.
+ cur = b
+ chain = []
+ elt = cur
+ while elt.next and elt.next[0] != default_next:
+ chain.append(elt.next[0])
+ elt = elt.next[0]
+ # Now remove the blocks in the chain from the current
+ # block list, so that they can be re-inserted.
+ l = []
+ for b in chain:
+ assert index[b] > i
+ l.append((index[b], b))
+ l.sort()
+ l.reverse()
+ for j, b in l:
+ del blocks[index[b]]
+ # Insert the chain in the proper location
+ blocks[i:i + 1] = [cur] + chain
+ # Finally, re-compute the block indexes
+ for i in range(len(blocks)):
+ index[blocks[i]] = i
+
+ def fixupOrderForward(self, blocks, default_next):
+ """Make sure all JUMP_FORWARDs jump forward"""
+ index = {}
+ chains = []
+ cur = []
+ for b in blocks:
+ index[b] = len(chains)
+ cur.append(b)
+ if b.next and b.next[0] == default_next:
+ chains.append(cur)
+ cur = []
+ chains.append(cur)
+
+ while 1:
+ constraints = []
+
+ for i in range(len(chains)):
+ l = chains[i]
+ for b in l:
+ for c in b.get_children():
+ if index[c] < i:
+ forward_p = 0
+ for inst in b.insts:
+ if inst[0] == 'JUMP_FORWARD':
+ if inst[1] == c:
+ forward_p = 1
+ if not forward_p:
+ continue
+ constraints.append((index[c], i))
+
+ if not constraints:
+ break
+
+ # XXX just do one for now
+ # do swaps to get things in the right order
+ goes_before, a_chain = constraints[0]
+ assert a_chain > goes_before
+ c = chains[a_chain]
+ chains.remove(c)
+ chains.insert(goes_before, c)
+
+
+ del blocks[:]
+ for c in chains:
+ for b in c:
+ blocks.append(b)
+
def getBlocks(self):
return self.blocks.elements()