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From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>,
	"aldyh@redhat.com" <aldyh@redhat.com>
Subject: Re: [PATCH] PR target/97312: Tweak gcc.target/aarch64/pr90838.c
Date: Thu, 8 Oct 2020 11:37:24 +0000	[thread overview]
Message-ID: <VE1PR08MB55993D689E3D2F418DC1CF5E830B0@VE1PR08MB5599.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <20201008112535.GT2176@tucnak>

Hi Jakub, 

> Having it undefined allows optimizations, and has been that way for years.

Which optimizations does it enable that aren't possible if the value is defined?

> We just should make sure that we optimize code like x ? __builtin_c[lt]z (x) : 32;
> etc. properly (and I believe we do).

I think we do, but both the external and internal documentation are not clear
enough that most targets actually do define a value and will optimize for it.
Otherwise we wouldn't have this bug now...

Cheers,
Wilco

  reply	other threads:[~2020-10-08 11:37 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-08 11:04 Wilco Dijkstra
2020-10-08 11:09 ` Jakub Jelinek
2020-10-08 11:22   ` Wilco Dijkstra
2020-10-08 11:25     ` Jakub Jelinek
2020-10-08 11:37       ` Wilco Dijkstra [this message]
2020-10-08 11:40         ` Jakub Jelinek
2020-10-08 12:57           ` Wilco Dijkstra
2020-10-08 11:30   ` Wilco Dijkstra
  -- strict thread matches above, loose matches on Subject: below --
2020-10-08 10:33 Wilco Dijkstra
2020-10-08  9:58 Aldy Hernandez
2020-10-08 10:22 ` Jakub Jelinek
2020-10-08 10:27   ` Jakub Jelinek

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