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Re: [PATCH] Expand switch statements with a single (or none) non-default case.
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Martin Liška <mliska at suse dot cz>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 30 Aug 2017 14:28:01 +0200
- Subject: Re: [PATCH] Expand switch statements with a single (or none) non-default case.
- Authentication-results: sourceware.org; auth=none
- References: <bde90963-7695-89d5-6792-e8f803f71160@suse.cz>
On Wed, Aug 30, 2017 at 1:13 PM, Martin Liška <mliska@suse.cz> wrote:
> Hi.
>
> Simple transformation of switch statements where degenerated switch can be interpreted
> as gimple condition (or removed if having any non-default case). I originally though
> that we don't have switch statements without non-default cases, but PR82032 shows we
> can see it.
>
> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>
> Ready to be installed?
While I guess this case is ok to handle here it would be nice if CFG cleanup
would do the same. I suppose find_taken_edge somehow doesn't work for
this case even after my last enhancement? Or is CFG cleanup for some reason
not run?
Richard.
> Martin
>
> gcc/ChangeLog:
>
> 2017-08-25 Martin Liska <mliska@suse.cz>
>
> PR tree-optimization/82032
> * tree-switch-conversion.c (generate_high_low_equality): New
> function.
> (expand_degenerated_switch): Likewise.
> (process_switch): Call expand_degenerated_switch.
> (try_switch_expansion): Likewise.
> (emit_case_nodes): Use generate_high_low_equality.
>
> gcc/testsuite/ChangeLog:
>
> 2017-08-25 Martin Liska <mliska@suse.cz>
>
> PR tree-optimization/82032
> * gcc.dg/tree-ssa/pr68198.c: Update jump threading expectations.
> * gcc.dg/tree-ssa/switch-expansion.c: New test.
> * gcc.dg/tree-ssa/vrp34.c: Update scanned pattern.
> * g++.dg/other/pr82032.C: New test.
> ---
> gcc/testsuite/g++.dg/other/pr82032.C | 36 +++++++
> gcc/testsuite/gcc.dg/tree-ssa/pr68198.c | 6 +-
> gcc/testsuite/gcc.dg/tree-ssa/switch-expansion.c | 14 +++
> gcc/testsuite/gcc.dg/tree-ssa/vrp34.c | 5 +-
> gcc/tree-switch-conversion.c | 123 ++++++++++++++++++-----
> 5 files changed, 152 insertions(+), 32 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/other/pr82032.C
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/switch-expansion.c
>
>