Re: [PATCH] Expand switch statements with a single (or none) non-default case.

[Richard Biener <richard.guenther@gmail.com>]

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
>
>