From: Thomas Wolff <towo@towo.net>
To: cygwin@cygwin.com
Subject: Re: [ANNOUNCEMENT] Test: {mingw64-{i686,x86_64}-,}gcc-11.1.0-0.1
Date: Thu, 13 May 2021 23:57:40 +0200 [thread overview]
Message-ID: <04176b59-1b36-c139-76b7-046e3823caa1@towo.net> (raw)
In-Reply-To: <5d911b7f-70c6-01f5-a353-d8735be46ecd@t-online.de>
Am 13.05.2021 um 21:33 schrieb Hans-Bernhard Bröker:
> Am 13.05.2021 um 10:57 schrieb Thomas Wolff:
>
>> The crash vanishes after removing a few lines from a conditional (if
>> block) where the condition is false.
>
> A conditions that's always false, or one that's false during the
> execution of a particular test case?
False during execution.
>
>> This smells like wrong calculation of a relative jump (Intel "short
>> jump") by the optimizer.
>
> If it were that simple, the problematic change should stand out like
> the proverbial sore thumb when comparing assembly listings of the two
> cases. Does it?
Not really. As the problem only occurs with -O2, I'd need to check the
result of gcc -S -O2, but with -O2, code is stirred so much it's hardly
recognizable. The conditional jump to skip the (dynamically false)
conditional is even a jump backwards in this case...
prev parent reply other threads:[~2021-05-13 21:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-10 19:13 Achim Gratz
2021-05-12 9:14 ` Thomas Wolff
2021-05-12 10:42 ` Jonathan Yong
2021-05-12 18:30 ` Thomas Wolff
2021-05-13 1:41 ` Brian Inglis
2021-05-13 2:22 ` Thomas Wolff
2021-05-12 18:53 ` Achim Gratz
2021-05-13 8:57 ` Thomas Wolff
2021-05-13 19:33 ` Hans-Bernhard Bröker
2021-05-13 21:57 ` Thomas Wolff [this message]
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