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Re: [RFC] Enable virtual operands at -O0
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 15 Apr 2014 18:00:22 +0200
- Subject: Re: [RFC] Enable virtual operands at -O0
- Authentication-results: sourceware.org; auth=none
- References: <6691503 dot GtiFGFCv1P at polaris>
On Tue, Apr 15, 2014 at 4:13 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> Hi,
>
> I recently stumbled on the ??? comment in tree-ssa-uninit.c and wondered why
> virtual operands are not enabled at -O0. As demonstrated by the attached
> patch, this would make it possible to unXFAIL a few uninit-*.c testcases.
>
> Tested on x86_64-suse-linux.
ISTR some more ???/FIXMEs and/or special-casings we could remove with
that. As followup, of course.
The single reason why we don't have virtual operands at -O0 is compile-time
btw - SSA rewrite doesn't come for free. But I don't mind - still maybe
a quick comparison of stage1-gcc compile-time with/without that patch
would be interesting?
Thanks,
Richard.
>
> * tree-ssa-operands.c (create_vop_var): Set DECL_IGNORED_P.
> (append_use): Run at -O0.
> (append_vdef): Likewise.
> * tree-ssa-uninit.c (warn_uninitialized_vars): Remove obsolete comment.
> testsuite/
> * gcc.dg/uninit-B-O0.c: Remove XFAIL.
> * gcc.dg/uninit-I-O0.c: Likewise.
> * gcc.dg/uninit-pr19430-O0.c: Remove some XFAILs.
>
>
> --
> Eric Botcazou