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Subject: Re: [PATCH] Add if-chain to switch conversion pass.
To: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Cc: Richard Biener <richard.guenther@gmail.com>, Jakub Jelinek <jakub@redhat.com>, GCC Patches <gcc-patches@gcc.gnu.org>, Jan Hubicka <hubicka@ucw.cz>
References: <2c3db526-cac6-4eeb-4afb-12024f8d5af2@suse.cz> <20191104144851.GJ4650@tucnak> <CAFiYyc0j3uYK9Z5LVtcoG0r9PhXB=Pj5kTy6vU0XzV7H=edO2A@mail.gmail.com> <20191106220256.4e7c63a6@nbbrfq.loc>
From: =?UTF-8?Q?Martin_Li=c5=a1ka?= <mliska@suse.cz>
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Date: Thu, 14 Nov 2019 09:44:00 -0000
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On 11/6/19 10:02 PM, Bernhard Reutner-Fischer wrote:
> Also why do you punt on duplicate conditions like in
> 
>> +++ b/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-4.c
>> +int main(int argc, char **argv)
>> +{
>> +  if (argc == 1)
>> +  else if (argc == 2)
>> +  else if (argc == 3)
>> +  else if (argc == 4)
>> +  else if (argc == 1)
>> +    {
> This block is dead, isn't it. Why don't you just discard it but punt?
> 

Hello.

After I moved the pass later in optimization pipeline, such dead conditions
are already gone. What's remaining are situations like:

if (argc >= 1 && argc <= 10)
...
else if (argc >= 8 && argc <= 15)

which are overlapping intervals. I'm not planning to handle these in the first
iteration of the patch.

Martin