c-common.c (c_expand_expr): If the last expression is a VAR_DECL with RTL that matches the target...

        * c-common.c (c_expand_expr) [STMT_EXPR]: If the last expression is
        a VAR_DECL with RTL that matches the target, just return that RTL.

From-SVN: r56083

1 files changed, 18 insertions, 3 deletions

diff --git a/gcc/c-common.c b/gcc/c-common.c
index fabc181..30c38de 100644
--- a/gcc/c-common.c
+++ b/gcc/c-common.c
@@ -4185,6 +4185,7 @@ c_expand_expr (exp, target, tmode, modifier)
 	tree rtl_expr;
 	rtx result;
 	bool preserve_result = false;
+	bool return_target = false;
 
 	/* Since expand_expr_stmt calls free_temp_slots after every
 	   expression statement, we must call push_temp_slots here.
@@ -4212,8 +4213,20 @@ c_expand_expr (exp, target, tmode, modifier)
 	    if (TREE_CODE (last) == SCOPE_STMT
 		&& TREE_CODE (expr) == EXPR_STMT)
 	      {
-	        TREE_ADDRESSABLE (expr) = 1;
-		preserve_result = true;
+		if (target && TREE_CODE (EXPR_STMT_EXPR (expr)) == VAR_DECL
+		    && DECL_RTL_IF_SET (EXPR_STMT_EXPR (expr)) == target)
+		  /* If the last expression is a variable whose RTL is the
+		     same as our target, just return the target; if it
+		     isn't valid expanding the decl would produce different
+		     RTL, and store_expr would try to do a copy.  */
+		  return_target = true;
+		else
+		  {
+		    /* Otherwise, note that we want the value from the last
+		       expression.  */
+		    TREE_ADDRESSABLE (expr) = 1;
+		    preserve_result = true;
+		  }
 	      }
 	  }
 
@@ -4221,7 +4234,9 @@ c_expand_expr (exp, target, tmode, modifier)
 	expand_end_stmt_expr (rtl_expr);
 
 	result = expand_expr (rtl_expr, target, tmode, modifier);
-	if (preserve_result && GET_CODE (result) == MEM)
+	if (return_target)
+	  result = target;
+	else if (preserve_result && GET_CODE (result) == MEM)
 	  {
 	    if (GET_MODE (result) != BLKmode)
 	      result = copy_to_reg (result);