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Re: timespec test failure on Linux/s390x

From: Paul Eggert
Subject: Re: timespec test failure on Linux/s390x
Date: Sun, 12 Sep 2021 12:40:03 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0

On 9/12/21 8:28 AM, Bruno Haible wrote:
I can't determine whether it's a GCC or a QEMU bug.

Surely it is a QEMU bug, as QEMU isn't properly implementing the z/Architecture Principles of Operation (POP). Page 7-25 of the current edition (SA22-7832-12) says that the AGR instruction treats its operands as 64-bit signed binary integers, and sets condition code 3 (the overflow flag) if the result overflows. You can get a copy of the POP here (requires registration):


The QEMU bug hypothesis
looks more probable to me, so I've opened this ticket:

The patch you submitted to QEMU looks reasonable. However, there are similar bugs in cc_calc_sub_32 and cc_calc_sub_64 that should also be fixed. I attempted to submit a comment to that effect on the gitlab.com website but couldn't easily figure out how to make commenting work there.

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