Re: [PATCH v2] Fix PR79908

[Richard Biener <richard dot guenther at gmail dot com>]

On Mon, Mar 20, 2017 at 8:15 PM, Bill Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> Hi,
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79908 shows a case where
> pass_stdarg ICEs attempting to gimplify a COMPLEX_EXPR with side
> effects as an lvalue.  This occurs when the LHS of a VA_ARG has been
> cast away.  This patch, credit to Richard Biener, uses
> force_gimple_operand to instantiate the necessary side effects rather
> than gimplify_expr using is_gimple_lvalue.  The test case is taken
> wholesale from the bug report.
>
> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no
> regressions.  Is this ok for trunk?

Ok!

Thanks,
Richard.

> Thanks,
> Bill
>
>
> [gcc]
>
> 2017-03-20  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
>             Richard Biener  <rguenth@suse.com>
>
>         PR tree-optimization/79908
>         * tree-stdarg.c (expand_ifn_va_arg_1): For a VA_ARG whose LHS has
>         been cast away, use force_gimple_operand to construct the side
>         effects.
>
> [gcc/testsuite]
>
> 2017-03-20  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
>             Richard Biener  <rguenther@suse.de>
>
>         PR tree-optimization/79908
>         * gcc.dg/torture/pr79908.c: New file.
>
>
> Index: gcc/testsuite/gcc.dg/torture/pr79908.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/torture/pr79908.c      (nonexistent)
> +++ gcc/testsuite/gcc.dg/torture/pr79908.c      (working copy)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +
> +/* Used to fail in the stdarg pass before fix for PR79908.  */
> +
> +typedef __builtin_va_list __gnuc_va_list;
> +typedef __gnuc_va_list va_list;
> +
> +void testva (int n, ...)
> +{
> +  va_list ap;
> +  _Complex int i = __builtin_va_arg (ap, _Complex int);
> +}
> Index: gcc/tree-stdarg.c
> ===================================================================
> --- gcc/tree-stdarg.c   (revision 246286)
> +++ gcc/tree-stdarg.c   (working copy)
> @@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "gimple-iterator.h"
>  #include "gimple-walk.h"
>  #include "gimplify.h"
> +#include "gimplify-me.h"
>  #include "tree-into-ssa.h"
>  #include "tree-cfg.h"
>  #include "tree-stdarg.h"
> @@ -1058,12 +1059,16 @@ expand_ifn_va_arg_1 (function *fun)
>             gimplify_assign (lhs, expr, &pre);
>           }
>         else
> -         gimplify_expr (&expr, &pre, &post, is_gimple_lvalue, fb_lvalue);
> +         {
> +           gimple_seq tmp_seq;
> +           force_gimple_operand (expr, &tmp_seq, false, NULL_TREE);
> +           gimple_seq_add_seq_without_update (&pre, tmp_seq);
> +         }
>
>         input_location = saved_location;
>         pop_gimplify_context (NULL);
>
> -       gimple_seq_add_seq (&pre, post);
> +       gimple_seq_add_seq_without_update (&pre, post);
>         update_modified_stmts (pre);
>
>         /* Add the sequence after IFN_VA_ARG.  This splits the bb right
> @@ -1072,11 +1077,10 @@ expand_ifn_va_arg_1 (function *fun)
>         gimple_find_sub_bbs (pre, &i);
>
>         /* Remove the IFN_VA_ARG gimple_call.  It's the last stmt in the
> -          bb.  */
> +          bb if we added any stmts.  */
>         unlink_stmt_vdef (stmt);
>         release_ssa_name_fn (fun, gimple_vdef (stmt));
>         gsi_remove (&i, true);
> -       gcc_assert (gsi_end_p (i));
>
>         /* We're walking here into the bbs which contain the expansion of
>            IFN_VA_ARG, and will not contain another IFN_VA_ARG that needs
>