From 744fbcdcd967bbf3124d7385a5ea10d0a56fff72 Mon Sep 17 00:00:00 2001
From: Noah Watson <107630091+nwatson22@users.noreply.github.com>
Date: Mon, 18 Sep 2023 03:23:45 -0500
Subject: [PATCH] Make branch extraction more intelligent (#652)
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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
https://github.com/runtimeverification/evm-semantics/pull/2065 when
creating new proofs from branches.

---------

Co-authored-by: devops <devops@runtimeverification.com>
Co-authored-by: Petar Maksimović <PetarMax@users.noreply.github.com>
---
 package/version         |  2 +-
 pyproject.toml          |  2 +-
 src/pyk/kcfg/explore.py | 21 +++++++++++++--------
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/package/version b/package/version
index 5abb16f50..8cc010e6a 100644
--- a/package/version
+++ b/package/version
@@ -1 +1 @@
-0.1.443
+0.1.444
diff --git a/pyproject.toml b/pyproject.toml
index 73447ac3a..7dcb3ba3c 100644
--- a/pyproject.toml
+++ b/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. <contact@runtimeverification.com>",
diff --git a/src/pyk/kcfg/explore.py b/src/pyk/kcfg/explore.py
index 0c77167a3..68cf785ef 100644
--- a/src/pyk/kcfg/explore.py
+++ b/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(