Introduce ssa_defined_default_def_p function (PR tree-optimization/79529).

2017-02-17  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/79529
	* tree-ssa-loop-unswitch.c (is_maybe_undefined): Use
	ssa_defined_default_def_p to handle cases which are implicitly
	defined.
	* tree-ssa.c (ssa_defined_default_def_p): New function.
	(ssa_undefined_value_p): Use ssa_defined_default_def_p to handle cases
	which are implicitly defined.
	* tree-ssa.h (ssa_defined_default_def_p): Declare.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@245530 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 33 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c7c6d59874f..defd5431ef1 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,14 @@
+2017-02-17  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/79529
+	* tree-ssa-loop-unswitch.c (is_maybe_undefined): Use
+	ssa_defined_default_def_p to handle cases which are implicitly
+	defined.
+	* tree-ssa.c (ssa_defined_default_def_p): New function.
+	(ssa_undefined_value_p): Use ssa_defined_default_def_p to handle cases
+	which are implicitly defined.
+	* tree-ssa.h (ssa_defined_default_def_p): Declare.
+
 2017-02-17  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/79576
diff --git a/gcc/tree-ssa-loop-unswitch.c b/gcc/tree-ssa-loop-unswitch.c
index afa04e9d110..1845148666d 100644
--- a/gcc/tree-ssa-loop-unswitch.c
+++ b/gcc/tree-ssa-loop-unswitch.c
@@ -134,9 +134,7 @@ is_maybe_undefined (const tree name, gimple *stmt, struct loop *loop)
       if (ssa_undefined_value_p (t, true))
 	return true;
 
-      /* A PARM_DECL will not have an SSA_NAME_DEF_STMT.  Parameters
-	 get their initial value from function entry.  */
-      if (SSA_NAME_VAR (t) && TREE_CODE (SSA_NAME_VAR (t)) == PARM_DECL)
+      if (ssa_defined_default_def_p (t))
 	continue;
 
       gimple *def = SSA_NAME_DEF_STMT (t);
diff --git a/gcc/tree-ssa.c b/gcc/tree-ssa.c
index 28020b003f8..831fd61e15f 100644
--- a/gcc/tree-ssa.c
+++ b/gcc/tree-ssa.c
@@ -1251,27 +1251,39 @@ tree_ssa_strip_useless_type_conversions (tree exp)
   return exp;
 }
 
-
-/* Return true if T, an SSA_NAME, has an undefined value.  PARTIAL is what
-   should be returned if the value is only partially undefined.  */
+/* Return true if T, as SSA_NAME, has an implicit default defined value.  */
 
 bool
-ssa_undefined_value_p (tree t, bool partial)
+ssa_defined_default_def_p (tree t)
 {
-  gimple *def_stmt;
   tree var = SSA_NAME_VAR (t);
 
   if (!var)
     ;
   /* Parameters get their initial value from the function entry.  */
   else if (TREE_CODE (var) == PARM_DECL)
-    return false;
+    return true;
   /* When returning by reference the return address is actually a hidden
      parameter.  */
   else if (TREE_CODE (var) == RESULT_DECL && DECL_BY_REFERENCE (var))
-    return false;
+    return true;
   /* Hard register variables get their initial value from the ether.  */
   else if (VAR_P (var) && DECL_HARD_REGISTER (var))
+    return true;
+
+  return false;
+}
+
+
+/* Return true if T, an SSA_NAME, has an undefined value.  PARTIAL is what
+   should be returned if the value is only partially undefined.  */
+
+bool
+ssa_undefined_value_p (tree t, bool partial)
+{
+  gimple *def_stmt;
+
+  if (ssa_defined_default_def_p (t))
     return false;
 
   /* The value is undefined iff its definition statement is empty.  */
diff --git a/gcc/tree-ssa.h b/gcc/tree-ssa.h
index 6d16ba9f6a0..c99b5eaee82 100644
--- a/gcc/tree-ssa.h
+++ b/gcc/tree-ssa.h
@@ -50,6 +50,8 @@ extern void delete_tree_ssa (function *);
 extern bool tree_ssa_useless_type_conversion (tree);
 extern tree tree_ssa_strip_useless_type_conversions (tree);
 
+
+extern bool ssa_defined_default_def_p (tree t);
 extern bool ssa_undefined_value_p (tree, bool = true);
 extern bool gimple_uses_undefined_value_p (gimple *);
 extern void execute_update_addresses_taken (void);