Make branch extraction more intelligent (#652)

Closes #632. Before introducing a branch, simplify each of the would-be new nodes and see if they simplify to bottom If there are more than 1 non-bottom node, add all these simplified nodes to the CFG, creating a split/branch. If not, simply continue straight-line execution. This should reduce eliminate some infeasible branching by simplifying earlier in the process. Also should eliminate repeated branching encountered in runtimeverification/evm-semantics#2065 when creating new proofs from branches. --------- Co-authored-by: devops <[email protected]> Co-authored-by: Petar Maksimović <[email protected]>
runtimeverification · Sep 18, 2023 · 620bd5e · 620bd5e
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diff --git a/pyk/package/version b/pyk/package/version
@@ -1 +1 @@
-0.1.443
+0.1.444
diff --git a/pyk/pyproject.toml b/pyk/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry]
 name = "pyk"
-version = "0.1.443"
+version = "0.1.444"
 description = ""
 authors = [
     "Runtime Verification, Inc. <[email protected]>",

diff --git a/pyk/src/pyk/kcfg/explore.py b/pyk/src/pyk/kcfg/explore.py
@@ -377,14 +377,19 @@ def extend(
         if self._check_abstract(node, kcfg):
             return
 
-        if not kcfg.splits(target_id=node.id):
-            branches = self.kcfg_semantics.extract_branches(node.cterm)
-            if branches:
-                kcfg.split_on_constraints(node.id, branches)
-                _LOGGER.info(
-                    f'Found {len(branches)} branches using heuristic for node {node.id}: {shorten_hashes(node.id)}: {[self.kprint.pretty_print(bc) for bc in branches]}'
-                )
-                return
+        _branches = self.kcfg_semantics.extract_branches(node.cterm)
+        branches = []
+        for constraint in _branches:
+            kast = mlAnd(list(node.cterm.constraints) + [constraint])
+            kast, _ = self.kast_simplify(kast)
+            if not CTerm._is_bottom(kast):
+                branches.append(constraint)
+        if len(branches) > 1:
+            kcfg.split_on_constraints(node.id, branches)
+            _LOGGER.info(
+                f'Found {len(branches)} branches using heuristic for node {node.id}: {shorten_hashes(node.id)}: {[self.kprint.pretty_print(bc) for bc in branches]}'
+            )
+            return
 
         _LOGGER.info(f'Extending KCFG from node {self.id}: {shorten_hashes(node.id)}')
         _is_vacuous, depth, cterm, next_cterms, next_node_logs = self.cterm_execute(