[C PATCH] Fix -Wunused-but-set-* on __builtin_shuffle (PR c/52577)

[Jakub Jelinek]

Hi!

We weren't calling mark_exp_read on these and thus we got false positive
-Wunused-but-set-* warnings.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok
for trunk/4.7.1?

For trunk we should add __builtin_shuffle support even for C++ I'd say.

2012-03-13  Jakub Jelinek  <ja...@redhat.com>

        PR c/52577
        * c-parser.c (c_parser_postfix_expression)
        <case RID_BUILTIN_SHUFFLE>: Call mark_exp_read on argument values.

        * gcc.dg/Wunused-var-3.c: New test.

--- gcc/c-parser.c.jj   2012-01-02 20:39:55.000000000 +0100
+++ gcc/c-parser.c      2012-03-13 09:51:51.582984837 +0100
@@ -1,7 +1,7 @@
 /* Parser for C and Objective-C.
    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
-   Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011,
+   2012 Free Software Foundation, Inc.
 
    Parser actions based on the old Bison parser; structure somewhat
    influenced by and fragments based on the C++ parser.
@@ -6647,6 +6647,8 @@ c_parser_postfix_expression (c_parser *p
        case RID_BUILTIN_SHUFFLE:
          {
            VEC(c_expr_t,gc) *cexpr_list;
+           unsigned int i;
+           c_expr_t *p;
 
            c_parser_consume_token (parser);
            if (!c_parser_get_builtin_args (parser,
@@ -6657,6 +6659,9 @@ c_parser_postfix_expression (c_parser *p
                break;
              }
 
+           FOR_EACH_VEC_ELT (c_expr_t, cexpr_list, i, p)
+             mark_exp_read (p->value);
+
            if (VEC_length (c_expr_t, cexpr_list) == 2)
              expr.value =
                c_build_vec_perm_expr
--- gcc/testsuite/gcc.dg/Wunused-var-3.c.jj     2012-03-13 09:52:53.802619513 
+0100
+++ gcc/testsuite/gcc.dg/Wunused-var-3.c        2012-03-13 09:53:00.589578859 
+0100
@@ -0,0 +1,34 @@
+/* PR c/52577 */
+/* { dg-do compile } */
+/* { dg-options "-Wunused" } */
+
+typedef int V __attribute__((vector_size (sizeof (int) * 4)));
+
+void
+f1 (V *p)
+{
+  V mask = { 1, 2, 3, 0 };
+  *p = __builtin_shuffle (*p, mask);
+}
+
+void
+f2 (V *p, V *q)
+{
+  V mask = { 1, 2, 3, 0 };
+  *p = __builtin_shuffle (*p, *q, mask);
+}
+
+void
+f3 (V *p, V *mask)
+{
+  V a = { 1, 2, 3, 0 };
+  *p = __builtin_shuffle (a, *mask);
+}
+
+void
+f4 (V *p, V *mask)
+{
+  V a = { 1, 2, 3, 0 };
+  V b = { 2, 3, 4, 1 };
+  *p = __builtin_shuffle (a, b, *mask);
+}

        Jakub