From 3d308034fafd626a4902e31c7e4d860c36c7456e Mon Sep 17 00:00:00 2001
From: David Malcolm <dmalcolm@redhat.com>
Date: Wed, 23 Oct 2019 10:12:46 -0400
Subject: [PATCH 39/95] analyzer: new files: call-string.{cc|h}

This patch adds call_string, a class for representing the
call stacks at a program_point, so that we can ensure that
paths through the code are interprocedurally valid.

gcc/ChangeLog:
	* analyzer/call-string.cc: New file.
	* analyzer/call-string.h: New file.
---
 gcc/analyzer/call-string.cc | 201 ++++++++++++++++++++++++++++++++++++++++++++
 gcc/analyzer/call-string.h  |  74 ++++++++++++++++
 2 files changed, 275 insertions(+)
 create mode 100644 gcc/analyzer/call-string.cc
 create mode 100644 gcc/analyzer/call-string.h

diff --git a/gcc/analyzer/call-string.cc b/gcc/analyzer/call-string.cc
new file mode 100644
index 0000000..796b5e7
--- /dev/null
+++ b/gcc/analyzer/call-string.cc
@@ -0,0 +1,201 @@
+/* Call stacks at program points.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   Contributed by David Malcolm <dmalcolm@redhat.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "gcc-plugin.h"
+#include "system.h"
+#include "coretypes.h"
+#include "pretty-print.h"
+#include "tree.h"
+#include "analyzer/call-string.h"
+#include "analyzer/supergraph.h"
+
+/* class call_string.  */
+
+/* call_string's copy ctor.  */
+
+call_string::call_string (const call_string &other)
+: m_return_edges (other.m_return_edges.length ())
+{
+  const return_superedge *e;
+  int i;
+  FOR_EACH_VEC_ELT (other.m_return_edges, i, e)
+    m_return_edges.quick_push (e);
+}
+
+/* call_string's assignment operator.  */
+
+call_string&
+call_string::operator= (const call_string &other)
+{
+  // would be much simpler if we could rely on vec<> assignment op
+  m_return_edges.truncate (0);
+  m_return_edges.reserve (other.m_return_edges.length (), true);
+  const return_superedge *e;
+  int i;
+  FOR_EACH_VEC_ELT (other.m_return_edges, i, e)
+    m_return_edges.quick_push (e);
+  return *this;
+}
+
+/* call_string's equality operator.  */
+
+bool
+call_string::operator== (const call_string &other) const
+{
+  if (m_return_edges.length () != other.m_return_edges.length ())
+    return false;
+  const return_superedge *e;
+  int i;
+  FOR_EACH_VEC_ELT (m_return_edges, i, e)
+    if (e != other.m_return_edges[i])
+      return false;
+  return true;
+}
+
+/* Print this to PP.  */
+
+void
+call_string::print (pretty_printer *pp) const
+{
+  pp_string (pp, "[");
+
+  const return_superedge *e;
+  int i;
+  FOR_EACH_VEC_ELT (m_return_edges, i, e)
+    {
+      if (i > 0)
+	pp_string (pp, ", ");
+      pp_printf (pp, "(SN: %i -> SN: %i in %s)",
+		 e->m_src->m_index, e->m_dest->m_index,
+		 function_name (e->m_dest->m_fun));
+    }
+
+  pp_string (pp, "]");
+}
+
+/* Generate a hash value for this call_string.  */
+
+hashval_t
+call_string::hash () const
+{
+  inchash::hash hstate;
+  int i;
+  const return_superedge *e;
+  FOR_EACH_VEC_ELT (m_return_edges, i, e)
+    hstate.add_ptr (e);
+  return hstate.end ();
+}
+
+/* Push the return superedge for CALL_SEDGE onto the end of this
+   call_string.  */
+
+void
+call_string::push_call (const supergraph &sg,
+			const call_superedge *call_sedge)
+{
+  gcc_assert (call_sedge);
+  const return_superedge *return_sedge = call_sedge->get_edge_for_return (sg);
+  gcc_assert (return_sedge);
+  m_return_edges.safe_push (return_sedge);
+}
+
+/* Count the number of times the top-most call site appears in the
+   stack.  */
+
+int
+call_string::calc_recursion_depth () const
+{
+  if (m_return_edges.is_empty ())
+    return 0;
+  const return_superedge *top_return_sedge
+    = m_return_edges[m_return_edges.length () - 1];
+
+  int result = 0;
+  const return_superedge *e;
+  int i;
+  FOR_EACH_VEC_ELT (m_return_edges, i, e)
+    if (e == top_return_sedge)
+      ++result;
+  return result;
+}
+
+/* Comparator for call strings.
+   Return negative if A is before B.
+   Return positive if B is after A.
+   Return 0 if they are equal.  */
+
+int
+call_string::cmp (const call_string &a,
+		  const call_string &b)
+{
+  int result = cmp_1 (a, b);
+
+  /* Check that the ordering is symmetric  */
+#if CHECKING_P
+  int reversed = cmp_1 (b, a);
+  gcc_assert (reversed == -result);
+#endif
+
+  /* We should only have 0 for equal pairs.  */
+  gcc_assert (result != 0
+	      || a == b);
+
+  return result;
+}
+
+/* Implementation of call_string::cmp.
+   This implements a version of lexicographical order.  */
+
+int
+call_string::cmp_1 (const call_string &a,
+		    const call_string &b)
+{
+  unsigned len_a = a.length ();
+  unsigned len_b = b.length ();
+
+  unsigned i = 0;
+  while (1)
+    {
+      /* Consider index i; the strings have been equal up to it.  */
+
+      /* Have both strings run out?  */
+      if (i >= len_a && i >= len_b)
+	return 0;
+
+      /* Otherwise, has just one of the strings run out?  */
+      if (i >= len_a)
+	return 1;
+      if (i >= len_b)
+	return -1;
+
+      /* Otherwise, compare the edges.  */
+      const return_superedge *edge_a = a[i];
+      const return_superedge *edge_b = b[i];
+      int src_cmp = edge_a->m_src->m_index - edge_b->m_src->m_index;
+      if (src_cmp)
+	return src_cmp;
+      int dest_cmp = edge_a->m_dest->m_index - edge_b->m_dest->m_index;
+      if (dest_cmp)
+	return dest_cmp;
+      i++;
+      // TODO: test coverage for this
+    }
+}
diff --git a/gcc/analyzer/call-string.h b/gcc/analyzer/call-string.h
new file mode 100644
index 0000000..e5657e6
--- /dev/null
+++ b/gcc/analyzer/call-string.h
@@ -0,0 +1,74 @@
+/* Call stacks at program points.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   Contributed by David Malcolm <dmalcolm@redhat.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_ANALYZER_CALL_STRING_H
+#define GCC_ANALYZER_CALL_STRING_H
+
+class supergraph;
+class call_superedge;
+class return_superedge;
+
+/* A string of return_superedge pointers, representing a call stack
+   at a program point.
+
+   This is used to ensure that we generate interprocedurally valid paths
+   i.e. that we return to the same callsite that called us.
+
+   The class actually stores the return edges, rather than the call edges,
+   since that's what we need to compare against.  */
+
+class call_string
+{
+public:
+  call_string () : m_return_edges () {}
+  call_string (const call_string &other);
+  call_string& operator= (const call_string &other);
+
+  bool operator== (const call_string &other) const;
+
+  void print (pretty_printer *pp) const;
+
+  hashval_t hash () const;
+
+  bool empty_p () const { return m_return_edges.is_empty (); }
+
+  void push_call (const supergraph &sg,
+		  const call_superedge *sedge);
+  const return_superedge *pop () { return m_return_edges.pop (); }
+
+  int calc_recursion_depth () const;
+
+  static int cmp (const call_string &a,
+		  const call_string &b);
+
+  unsigned length () const { return m_return_edges.length (); }
+  const return_superedge *operator[] (unsigned idx) const
+  {
+    return m_return_edges[idx];
+  }
+
+private:
+  static int cmp_1 (const call_string &a,
+		    const call_string &b);
+
+  auto_vec<const return_superedge *> m_return_edges;
+};
+
+#endif /* GCC_ANALYZER_CALL_STRING_H */
-- 
1.8.5.3

