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Date:      Fri, 22 May 2020 18:23:37 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 246630] stable/11 regression: base.txz reproducibility depends on number of cpu cores
Message-ID:  <bug-246630-227-Y4okZmveRr@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-246630-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-246630-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=246630

--- Comment #7 from Conrad Meyer <cem@freebsd.org> ---
Diff seems to start here (I reordered lines for clarity):

│ @@ -63992,183658 +63992,183673 @@
...
│ -  43c7b5:    49 89 cd                mov    %rcx,%r13
│ +  43c7b5:    49 89 cf                mov    %rcx,%r15

// ^^ r13 -> r15

│ -  43c7b8:    49 29 c5                sub    %rax,%r13
│ +  43c7b8:    49 29 c7                sub    %rax,%r15

│ -  43c7bb:    4c 89 ec                mov    %r13,%rsp
│ +  43c7bb:    4c 89 fc                mov    %r15,%rsp

...

│ -  43c803:    4c 63 c2                movslq %edx,%r8
│ +  43c803:    4c 63 da                movslq %edx,%r11

// ^^ r8 -> r11

│ -  43c806:    49 c1 e0 03             shl    $0x3,%r8
│ +  43c806:    49 c1 e3 03             shl    $0x3,%r11

│ -  43c80a:    4c 03 05 e7 7a bc 00    add    0xbc7ae7(%rip),%r8        #
0x10042f8
│ +  43c80a:    4c 03 1d e7 7a bc 00    add    0xbc7ae7(%rip),%r11        #
0x10042f8

│ -  43c811:    4c 89 05 d0 7a bc 00    mov    %r8,0xbc7ad0(%rip)        #
0x10042e8
│ +  43c811:    4c 89 1d d0 7a bc 00    mov    %r11,0xbc7ad0(%rip)        #
0x10042e8

│ -  43c818:    4c 3b 05 d1 7a bc 00    cmp    0xbc7ad1(%rip),%r8        #
0x10042f0
│ +  43c818:    4c 3b 1d d1 7a bc 00    cmp    0xbc7ad1(%rip),%r11        #
0x10042f0

│    43c81f:    76 07                   jbe    0x43c828
│ -  43c821:    4c 89 05 c8 7a bc 00    mov    %r8,0xbc7ac8(%rip)        #
0x10042f0
│ +  43c821:    4c 89 1d c8 7a bc 00    mov    %r11,0xbc7ac8(%rip)        #
0x10042f0


These particular changes are not the ones that affect code *size* (those must
be later), but do show reproducibility problems.

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