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Re: [PATCH] Teach VRP to truncate the case ranges of a switch
On 2016.08.03 at 15:47 +0200, Richard Biener wrote:
> On Wed, Aug 3, 2016 at 6:00 AM, Patrick Palka <patrick@parcs.ath.cx> wrote:
> > VRP currently has functionality to eliminate case labels that lie
> > completely outside of the switch operand's value range. This patch
> > complements this functionality by teaching VRP to also truncate the case
> > label ranges that partially overlap with the operand's value range.
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu. Does this look like
> > a reasonable optimization? Admittedly, its effect will almost always be
> > negligible except in cases where a case label range spans a large number
> > of values which is a pretty rare thing. The optimization triggered
> > about 250 times during bootstrap.
>
> I think it's most useful when the range collapses to a single value.
>
> Ok.
Apparently typedefs aren't handled correctly, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72810
--
Markus