Author: Ronan Lamy <ronan.l...@gmail.com>
Branch: ssa-flow
Changeset: r74514:273f7c704efb
Date: 2014-11-13 23:49 +0000
http://bitbucket.org/pypy/pypy/changeset/273f7c704efb/
Log: create remove_trivial_links(): the SSA version of join_blocks()
diff --git a/rpython/translator/simplify.py b/rpython/translator/simplify.py
--- a/rpython/translator/simplify.py
+++ b/rpython/translator/simplify.py
@@ -246,6 +246,44 @@
seen.append(case)
block.recloseblock(*exits)
+def remove_trivial_links(graph):
+ """Remove trivial links by merging their source and target blocks
+
+ A link is trivial if it only renames variables, is the single exit of its
+ source and the single parent of its target.
+ """
+ entrymap = mkentrymap(graph)
+ block = graph.startblock
+ seen = set([block])
+ stack = list(block.exits)
+ renaming = {}
+ while stack:
+ link = stack.pop()
+ if link.target in seen:
+ continue
+ source = link.prevblock
+ target = link.target
+ if (source.exitswitch is None and len(entrymap[target]) == 1 and
+ target.exits): # stop at the returnblock
+ assert len(source.exits) == 1
+ for vprev, vtarg in zip(link.args, target.inputargs):
+ while vprev in renaming:
+ vprev = renaming[vprev]
+ renaming[vtarg] = vprev
+ target.renamevariables(renaming)
+ source.operations.extend(target.operations)
+ source.exitswitch = newexitswitch = target.exitswitch
+ exits = target.exits
+ source.recloseblock(*exits)
+ if isinstance(newexitswitch, Constant) and newexitswitch !=
c_last_exception:
+ exits = replace_exitswitch_by_constant(source, newexitswitch)
+ stack.extend(exits)
+ else:
+ target.renamevariables(renaming)
+ seen.add(target)
+ stack.extend(target.exits)
+
+
def join_blocks(graph):
"""Links can be deleted if they are the single exit of a block and
the single entry point of the next block. When this happens, we can
@@ -962,9 +1000,9 @@
all_passes = [
eliminate_empty_blocks,
+ remove_assertion_errors,
+ remove_trivial_links,
SSA_to_SSI,
- remove_assertion_errors,
- join_blocks,
coalesce_bool,
transform_dead_op_vars,
remove_identical_vars,
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