re PR middle-end/45852 (volatile structs are broken!)

	PR middle-end/45852
	* expr.c (store_expr): Ignore alt_rtl if equal to target,
	but has side-effects.

	* gcc.target/i386/pr45852.c: New test.

From-SVN: r168105

gcc/ChangeLog

+2010-12-21  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/45852
+	* expr.c (store_expr): Ignore alt_rtl if equal to target,
+	but has side-effects.
+
 2010-12-21  Anatoly Sokolov  <aesok@post.ru>
 
 	* config/sh/sh.h (PREFERRED_RELOAD_CLASS): Remove.

gcc/expr.c

@@ -4712,7 +4712,10 @@ store_expr (tree exp, rtx target, int call_param_p, bool nontemporal)
       /* If store_expr stores a DECL whose DECL_RTL(exp) == TARGET,
 	 but TARGET is not valid memory reference, TEMP will differ
 	 from TARGET although it is really the same location.  */
-      && !(alt_rtl && rtx_equal_p (alt_rtl, target))
+      && !(alt_rtl
+	   && rtx_equal_p (alt_rtl, target)
+	   && !side_effects_p (alt_rtl)
+	   && !side_effects_p (target))
       /* If there's nothing to copy, don't bother.  Don't call
 	 expr_size unless necessary, because some front-ends (C++)
 	 expr_size-hook must not be given objects that are not

gcc/testsuite/ChangeLog

+2010-12-21  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/45852
+	* gcc.target/i386/pr45852.c: New test.
+
 2010-12-20  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/46974

gcc/testsuite/gcc.target/i386/pr45852.c

+/* PR middle-end/45852 */
+/* { dg-options "-O2 -mcmodel=small" } */
+/* { dg-do compile { target { { i?86-*-linux* x86_64-*-linux* } && lp64 } } } */
+/* { dg-require-visibility "" } */
+
+struct S { int s; };
+
+volatile struct S globvar __attribute__((visibility ("hidden"))) = { -6 };
+
+void
+foo (void)
+{
+  globvar = globvar;
+}
+
+/* { dg-final { scan-assembler-times "globvar.%?rip" 2 } } */