* stmt.c (expand_expr_stmt): Keep last_expr_value non-NULL iff

we're interested in the result.  Use it to tell whether to
ignore results of enclosed expressions.
(expand_start_stmt_expr): Added new argument, and initialize
last_expr_value accordingly.
* tree.h (expand_start_stmt_expr): Adjusted declaration.
* c-common.c (c_expand_expr): Adjust call.
* expr.c (expand_expr) [EXPR_WFL]: Pass const0_rtx down if
ignoring the result.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@47607 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 15 insertions, 3 deletions

diff --git a/gcc/stmt.c b/gcc/stmt.c
index 2b176bb9e9a..bfac270dd52 100644
--- a/gcc/stmt.c
+++ b/gcc/stmt.c
@@ -2149,6 +2149,8 @@ void
 expand_expr_stmt (exp)
      tree exp;
 {
+  bool want_value = last_expr_value != NULL_RTX;
+
   /* If -W, warn about statements with no side effects,
      except for an explicit cast to void (e.g. for assert()), and
      except inside a ({...}) where they may be useful.  */
@@ -2175,7 +2177,7 @@ expand_expr_stmt (exp)
      last_expr_value to get reset.  Therefore, we set last_expr_value
      and last_expr_type *after* calling expand_expr.  */
   last_expr_value = expand_expr (exp,
-				 (expr_stmts_for_value
+				 (want_value && expr_stmts_for_value
 				  ? NULL_RTX : const0_rtx),
 				 VOIDmode, 0);
   last_expr_type = TREE_TYPE (exp);
@@ -2188,7 +2190,7 @@ expand_expr_stmt (exp)
       if (TYPE_MODE (TREE_TYPE (exp)) == VOIDmode)
 	;
       else if (TYPE_MODE (TREE_TYPE (exp)) != BLKmode)
-	copy_to_reg (last_expr_value);
+	last_expr_value = copy_to_reg (last_expr_value);
       else
 	{
 	  rtx lab = gen_label_rtx ();
@@ -2211,6 +2213,14 @@ expand_expr_stmt (exp)
      above.  */
   free_temp_slots ();
 
+  if (! want_value && last_expr_value)
+    {
+      protect_from_queue (last_expr_value, 0);
+      last_expr_value = NULL_RTX;
+    }
+  else if (want_value && ! last_expr_value)
+    last_expr_value = const0_rtx;
+
   emit_queue ();
 }
 
@@ -2336,7 +2346,8 @@ clear_last_expr ()
    The caller must save that value and pass it to expand_end_stmt_expr.  */
 
 tree
-expand_start_stmt_expr ()
+expand_start_stmt_expr (want_value)
+     int want_value;
 {
   tree t;
 
@@ -2347,6 +2358,7 @@ expand_start_stmt_expr ()
   start_sequence_for_rtl_expr (t);
   NO_DEFER_POP;
   expr_stmts_for_value++;
+  last_expr_value = want_value ? const0_rtx : NULL_RTX;
   return t;
 }