From: Matheus Castanho <msc@linux.ibm.com>
To: DJ Delorie <dj@redhat.com>
Cc: Florian Weimer <fweimer@redhat.com>, libc-alpha@sourceware.org
Subject: Re: [patch/idea] Add register scrambling to testsuite
Date: Mon, 13 Jun 2022 15:41:53 -0300 [thread overview]
Message-ID: <87ilp4tmzk.fsf@linux.ibm.com> (raw)
In-Reply-To: <xnleu0o6fh.fsf@greed.delorie.com>
Hi DJ,
DJ Delorie via Libc-alpha <libc-alpha@sourceware.org> writes:
> Florian Weimer <fweimer@redhat.com> writes:
>> This funcationality is likely more easily written as an assembler
>> routine that expects a function pointer and closure argument, performs
>> the register clobbers, and then calls the function with the closure
>> argument.
>
> I thought of putting the scramble just before the do_test calls, but
> there were more than one of those, and for the cases I'm trying to
> avoid, it doesn't matter when the regs are clobbered.
>
I was actually working on a patch similar to this one, but looks like
you beat me to it =). And you version seems cleaner.
You could embed your call to support_scramble_registers() in the CALL
macro on test-string.h:
#define CALL(impl, ...) \
({ support_scramble_registers (); (* (proto_t) (impl)->fn) (__VA_ARGS__); })
This way it would apply for all optimized function calls without
requiring many more changes. It also wouldn't affect the string
benchtests, since they use a separate CALL definition from
bench-string.h
> Calling scramble once is enough to more accurately simulate a "busy app"
> where gcc would have eventually filled all the registers with something,
> which is what happened in the bug I referenced. A closure-based asm
> routine would make the work much more complicated, for no real benefit.
>
> I've seen testsuites where each call-under-test was wrapped in a routine
> that called it multiple times, permuting the "untouched" registers each
> time. I don't think we need to go that far.
--
Matheus Castanho
next prev parent reply other threads:[~2022-06-13 18:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-11 3:52 DJ Delorie
2022-06-11 21:18 ` Noah Goldstein
2022-06-13 7:13 ` Florian Weimer
2022-06-13 16:48 ` DJ Delorie
2022-06-13 18:41 ` Matheus Castanho [this message]
2022-06-13 19:36 ` DJ Delorie
2022-06-13 16:44 ` DJ Delorie
2022-06-13 4:48 ` Jeff Law
2022-06-13 16:43 ` DJ Delorie
2022-06-16 7:46 ` Fangrui Song
2022-06-13 7:42 ` Siddhesh Poyarekar
2022-06-13 16:52 ` DJ Delorie
2022-06-14 5:43 ` Siddhesh Poyarekar
2022-06-14 16:11 ` DJ Delorie
2022-06-14 3:42 ` H.J. Lu
2022-06-14 4:01 ` Noah Goldstein
2022-06-14 4:07 ` DJ Delorie
2022-06-14 4:03 ` DJ Delorie
2022-06-13 12:04 Wilco Dijkstra
2022-06-13 13:33 ` Florian Weimer
2022-06-16 10:29 ` Wilco Dijkstra
2022-06-18 3:54 ` DJ Delorie
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