cfgexpand.c (expand_used_vars): Allocate space for partitions based on PARM_DECLs or RESULT_DECLs only if...

	* cfgexpand.c (expand_used_vars): Allocate space for partitions based
	on PARM_DECLs or RESULT_DECLs only if they are ignored for debug info
	or if optimization is enabled.
	* tree-ssa-coalesce.c (coalesce_ssa_name): If optimization is disabled,
	require that all the names based on a PARM_DECL or a RESULT_DECL that
	isn't ignored for debug info be coalesced.

From-SVN: r204742

5 files changed, 52 insertions, 5 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d03d52b..56d0397 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2013-11-13  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* cfgexpand.c (expand_used_vars): Allocate space for partitions based
+	on PARM_DECLs or RESULT_DECLs only if they are ignored for debug info
+	or if optimization is enabled.
+	* tree-ssa-coalesce.c (coalesce_ssa_name): If optimization is disabled,
+	require that all the names based on a PARM_DECL or a RESULT_DECL that
+	isn't ignored for debug info be coalesced.
+
 2013-11-13  Jan-Benedict Glaw  <jbglaw@lug-owl.de>
 
 	* config/c6x/c6x.c: Include "gimple-expr.h".
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 4e622c0..de7a7b3 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1610,9 +1610,15 @@ expand_used_vars (void)
 	  replace_ssa_name_symbol (var, (tree) *slot);
 	}
 
+      /* Always allocate space for partitions based on VAR_DECLs.  But for
+	 those based on PARM_DECLs or RESULT_DECLs and which matter for the
+	 debug info, there is no need to do so if optimization is disabled
+	 because all the SSA_NAMEs based on these DECLs have been coalesced
+	 into a single partition, which is thus assigned the canonical RTL
+	 location of the DECLs.  */
       if (TREE_CODE (SSA_NAME_VAR (var)) == VAR_DECL)
 	expand_one_var (var, true, true);
-      else
+      else if (DECL_IGNORED_P (SSA_NAME_VAR (var)) || optimize)
 	{
 	  /* This is a PARM_DECL or RESULT_DECL.  For those partitions that
 	     contain the default def (representing the parm or result itself)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index df1ee9a..d32d1be 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-13  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc.dg/guality/param-4.c: New test.
+
 2013-11-13  Joseph Myers  <joseph@codesourcery.com>
 
 	* gcc.dg/c11-complex-1.c: New test.
diff --git a/gcc/testsuite/gcc.dg/guality/param-4.c b/gcc/testsuite/gcc.dg/guality/param-4.c
new file mode 100644
index 0000000..a76b251f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/guality/param-4.c
@@ -0,0 +1,20 @@
+/* { dg-do run } */
+/* { dg-options "-g" } */
+/* { dg-skip-if "" { *-*-* }  { "*" } { "-O0" } } */
+
+void
+foo (int i)
+{
+  int j = 0;
+  i = 1;
+  j = j + 1;  /* BREAK */
+}
+
+int
+main (void)
+{
+  foo (0);
+  return 0;
+}
+
+/* { dg-final { gdb-test 10 "i" "1" } } */
\ No newline at end of file
diff --git a/gcc/tree-ssa-coalesce.c b/gcc/tree-ssa-coalesce.c
index c445c78..252fc33 100644
--- a/gcc/tree-ssa-coalesce.c
+++ b/gcc/tree-ssa-coalesce.c
@@ -1256,8 +1256,8 @@ coalesce_ssa_name (void)
   cl = create_coalesce_list ();
   map = create_outofssa_var_map (cl, used_in_copies);
 
-  /* We need to coalesce all names originating same SSA_NAME_VAR
-     so debug info remains undisturbed.  */
+  /* If optimization is disabled, we need to coalesce all the names originating
+     from the same SSA_NAME_VAR so debug info remains undisturbed.  */
   if (!optimize)
     {
       hash_table <ssa_name_var_hash> ssa_name_hash;
@@ -1278,8 +1278,16 @@ coalesce_ssa_name (void)
 		*slot = a;
 	      else
 		{
-		  add_coalesce (cl, SSA_NAME_VERSION (a), SSA_NAME_VERSION (*slot),
-				MUST_COALESCE_COST - 1);
+		  /* If the variable is a PARM_DECL or a RESULT_DECL, we
+		     _require_ that all the names originating from it be
+		     coalesced, because there must be a single partition
+		     containing all the names so that it can be assigned
+		     the canonical RTL location of the DECL safely.  */
+		  const int cost
+		    = TREE_CODE (SSA_NAME_VAR (a)) == VAR_DECL
+		      ? MUST_COALESCE_COST - 1 : MUST_COALESCE_COST;
+		  add_coalesce (cl, SSA_NAME_VERSION (a),
+				SSA_NAME_VERSION (*slot), cost);
 		  bitmap_set_bit (used_in_copies, SSA_NAME_VERSION (a));
 		  bitmap_set_bit (used_in_copies, SSA_NAME_VERSION (*slot));
 		}