From: David Hildenbrand <david@redhat.com>
To: Ilya Leoshkevich <iii@linux.ibm.com>,
Richard Henderson <richard.henderson@linaro.org>
Cc: Thomas Huth <thuth@redhat.com>,
qemu-s390x@nongnu.org, qemu-devel@nongnu.org,
Michael Tokarev <mjt@tls.msk.ru>
Subject: Re: [PATCH 0/4] target/s390x: CC fixes
Date: Fri, 3 Nov 2023 18:02:27 +0100 [thread overview]
Message-ID: <84b89d5d-96f5-45ab-b38a-be6699cc5260@redhat.com> (raw)
In-Reply-To: <cbbffb85272fab70d1051d98ce024031215afe6e.camel@linux.ibm.com>
On 03.11.23 17:44, Ilya Leoshkevich wrote:
> On Tue, 2023-10-31 at 09:38 +0100, David Hildenbrand wrote:
>> On 31.10.23 06:32, Ilya Leoshkevich wrote:
>>> Hi,
>>>
>>> This series fixes two issues with updating CC. David was suggesting
>>> a
>>> bigger rewrite [1], but I did not dare do this (yet). Instead,
>>> these
>>
>> I started coding that up but was distracted by other things; last
>> time I
>> looked at that, I concluded that the way we are calculating the carry
>> in
>> not suitable when we're doing two additions (like ADD LOGICAL WITH
>> CARRY).
>
> Do you per chance remember any details? IIUC the code in question is:
Unfortunately, I don't. I thought there would be a case where we could
overflow twice, and result in a carry value of 2. Or some other weird
corner case where the result would not be expressive.
Maybe I was daydreaming, let me see if I can re-discover what I found
(should have taken notes but was just briefly looking at this).
If not, your fixes might be just good enough.
--
Cheers,
David / dhildenb
prev parent reply other threads:[~2023-11-03 17:03 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-31 5:32 [PATCH 0/4] target/s390x: CC fixes Ilya Leoshkevich
2023-10-31 5:32 ` [PATCH 1/4] target/s390x: Fix CLC corrupting cc_src Ilya Leoshkevich
2023-10-31 22:49 ` Richard Henderson
2023-10-31 5:32 ` [PATCH 2/4] tests/tcg/s390x: Test CLC with inaccessible second operand Ilya Leoshkevich
2023-10-31 22:53 ` Richard Henderson
2023-11-06 9:20 ` Ilya Leoshkevich
2023-10-31 5:32 ` [PATCH 3/4] target/s390x: Fix LAALG not updating cc_src Ilya Leoshkevich
2023-10-31 22:57 ` Richard Henderson
2023-10-31 5:32 ` [PATCH 4/4] tests/tcg/s390x: Test LAALG with negative cc_src Ilya Leoshkevich
2023-10-31 8:38 ` [PATCH 0/4] target/s390x: CC fixes David Hildenbrand
2023-11-03 16:44 ` Ilya Leoshkevich
2023-11-03 17:02 ` David Hildenbrand [this message]
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