From 6f86087091c5a77e91a711a180550ba35c3f58b5 Mon Sep 17 00:00:00 2001
From: David Malcolm <dmalcolm@redhat.com>
Date: Thu, 2 Jul 2020 16:15:44 -0400
Subject: [PATCH 281/315] FIXME: implement pointer comparisons of
 INIT_VAL(PARM) with &LOCAL

---
 gcc/analyzer/region-model2.cc | 37 ++++++++++++++++++++++++++++-------
 gcc/analyzer/region-model2.h  |  2 ++
 2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/gcc/analyzer/region-model2.cc b/gcc/analyzer/region-model2.cc
index 08ccd8ceea2..4579ebd7c5a 100644
--- a/gcc/analyzer/region-model2.cc
+++ b/gcc/analyzer/region-model2.cc
@@ -6288,12 +6288,8 @@ region_model2::eval_condition_without_cm (const svalue2 *lhs,
 	    }
 	}
 
-  /* Initial values of "external" values (such as params) can't point
-     at locals.  */
-  // FIXME: what about other "external" values vs escaped clusters
-  /* Initial values of pointers can't point at locals.
-     FIXME: unless they escaped?  */
-#if 0
+  /* Handle rejection of equality for comparisons of the initial values of
+     "external" values (such as params) with the address of locals.  */
   if (const initial_svalue2 *init_lhs = lhs->dyn_cast_initial_svalue2 ())
     if (const region_svalue2 *rhs_ptr = rhs->dyn_cast_region_svalue2 ())
       {
@@ -6308,7 +6304,6 @@ region_model2::eval_condition_without_cm (const svalue2 *lhs,
 	if (res.is_known ())
 	  return res;
       }
-#endif
 
   if (const widening_svalue2 *widen_lhs = lhs->dyn_cast_widening_svalue2 ())
     if (tree rhs_cst = rhs->maybe_get_constant ())
@@ -6327,6 +6322,34 @@ region_model2::eval_condition_without_cm (const svalue2 *lhs,
   return tristate::TS_UNKNOWN;
 }
 
+/* Subroutine of region_model2::eval_condition_without_cm, for rejecting
+   equality of INIT_VAL(PARM) with &LOCAL.  */
+
+tristate
+region_model2::compare_initial_and_pointer (const initial_svalue2 *init,
+					    const region_svalue2 *ptr) const
+{
+  const region2 *pointee = ptr->get_pointee ();
+
+  /* If we have a pointer to something within a stack frame, it can't be the
+     initial value of a param.  */
+  if (pointee->maybe_get_frame_region ())
+    {
+      const region2 *reg = init->get_region ();
+      if (tree reg_decl = reg->maybe_get_decl ())
+	if (TREE_CODE (reg_decl) == SSA_NAME)
+	  {
+	    tree ssa_name = reg_decl;
+	    if (SSA_NAME_IS_DEFAULT_DEF (ssa_name)
+		&& SSA_NAME_VAR (ssa_name)
+		&& TREE_CODE (SSA_NAME_VAR (ssa_name)) == PARM_DECL)
+	      return tristate::TS_FALSE;
+	  }
+    }
+
+  return tristate::TS_UNKNOWN;
+}
+
 /* Attempt to add the constraint "LHS OP RHS" to this region_model2.
    If it is consistent with existing constraints, add it, and return true.
    Return false if it contradicts existing constraints.
diff --git a/gcc/analyzer/region-model2.h b/gcc/analyzer/region-model2.h
index a57a8da5c18..c0520d5c985 100644
--- a/gcc/analyzer/region-model2.h
+++ b/gcc/analyzer/region-model2.h
@@ -2393,6 +2393,8 @@ class region_model2
   tristate eval_condition_without_cm (const svalue2 *lhs,
 				      enum tree_code op,
 				      const svalue2 *rhs) const;
+  tristate compare_initial_and_pointer (const initial_svalue2 *init,
+					const region_svalue2 *ptr) const;
   tristate eval_condition (tree lhs,
 			   enum tree_code op,
 			   tree rhs,
-- 
2.26.2