[23.10 FEAT] libgmp SIMD optimizations

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Optimize the GNU MP Bignum Library using vector instructions.

- Requirement for Full Homomorphic Encryption, libgmp is used as a backend for NTL
- libgmp performance is critical also for GNU Cobol on Z.
Here a customer requested using packed decimal instructions in libgmp which does not appear to fit for libgmp - however SIMD would help on distros with ALS z13

https://gmplib.org/#STATUS

[Frank Heimes (fheimes)]

Please let us know the version the SIMD optimizations are going to land in.

[Frank Heimes (fheimes)]

Any updates on the version required to get this?

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2021-05-18 04:53 EDT-------
Feature will be introduced wiht libgmp > 6.2.1. Will keep you updated

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2021-08-05 08:58 EDT-------
An updated version of the patches has been posted on the mailing list waiting for review. The patch will go into unstable branch first but we will provide a backport for 6.2 stable branch:

https://gmplib.org/list-archives/gmp-devel/2021-August/006005.html

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------- Comment From <email address hidden> 2021-09-09 04:26 EDT-------
Fix didn't make it into impish / 21.10, hence moving to 22.04
Changing IBM BZ Target Milestone:21.10->22.04

[Frank Heimes (fheimes)]

I can see the z13 patches mentioned still here:
https://gmplib.org/list-archives/gmp-devel/2021-August/006005.html
and here:
https://gmplib.org/list-archives/gmp-devel/2021-November/006059.html
Looks like they are still not upstream accepted yet
and there is no (pre-)release of > 6.2.1 available yet.
Leave this ticket aside for now.

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2022-03-14 06:55 EDT-------
The required patches are still not upstream accepted, and with that, not in time for jammy.
Therefore, moving this item to Ubuntu 22.10
Changing target milestone: -> 22.10

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------- Comment From <email address hidden> 2022-08-26 06:05 EDT-------
Still not upstream accepted yet, therefore we need to move this to Ubuntu 23.04
Changing target milestone: -> 23.04

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------- Comment From <email address hidden> 2023-01-18 05:50 EDT-------
Making good progress, but will not make it in time for Lunar, therefore we need to postpone to 23.10.

Changing target milestone to: 23.10

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------- Comment From <email address hidden> 2023-07-11 08:24 EDT-------
The patches are now committed:
"Improved s390/z13 support from IBM."
https://gmplib.org/repo/gmp/rev/3a1d9af8b317

I've also added the upstream commit as is and added it to
libgmp10/lunar,now 2:6.2.1+dfsg1-1.1ubuntu1 s390x

In order to get use of it, you have to select those optimizations.
As the current gcc ALS is z13, we can just use the z13 code-paths as default by selecting those like this:

in debian/rules:
ifneq (,$(filter $(DEB_HOST_ARCH), mips64 mips64el))
confflags += ABI=64
endif

+ifneq (,$(filter $(DEB_HOST_ARCH), s390x))
+ confflags += MPN_PATH="s390_64/z13 s390_64 generic"
+endif

confflags_ma = $(confflags) $(confflags_build) --libdir=/usr/lib/$(DEB_HOST_MULTIARCH)

[Frank Heimes (fheimes)]

Thx Stefan, looks pretty straight forward - nicely prepared!
Guess it's a bit challenging to test properly.
I've just created test builds that are available here:
https://launchpad.net/~fheimes/+archive/ubuntu/lp1926752

debdiff is attached

[Frank Heimes (fheimes)]

Uploaded to mantic with slightly modified changelog (compared to attached debdiff):
  * Add d/p/debian/patches/0014-improved_s390_z13_support_from_ibm.patch
    to incl. improved optimizations for s390x, based on z13. (LP: #1926752)
    Also requires to expand d/rules to select the s390x (z13) specific
    optimizations by expanding MPN_PATH with the z13 code-path in confflags.

[Frank Heimes (fheimes)]

It's (surprisingly) a package from main, hence needs sponsorship.
Subscribing 'ubuntu-sponsors'.

[Frank Heimes (fheimes)]

added updated debdiff

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Default Comment by Bridge

[Graham Inggs (ginggs)]

I sponsored the upload to mantic

[Frank Heimes (fheimes)]

Many thx for your sponsorship, Graham!

[Launchpad Janitor (janitor)]

This bug was fixed in the package gmp - 2:6.2.1+dfsg1-1.1ubuntu2

---------------
gmp (2:6.2.1+dfsg1-1.1ubuntu2) mantic; urgency=medium

  * Add d/p/debian/patches/0014-improved_s390_z13_support_from_ibm.patch
    to incl. improved optimizations for s390x, based on z13. (LP: #1926752)
    Also requires to expand d/rules to select the s390x (z13) specific
    optimizations by expanding MPN_PATH with the z13 code-path in confflags.

 -- Frank Heimes <email address hidden> Wed, 12 Jul 2023 10:56:34 +0200

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------- Comment From <email address hidden> 2023-07-21 05:29 EDT-------
I've installed libgmp-dev, libgmp10 from matic in version 2:6.2.1+dfsg1-1.1ubuntu2 and GMPbench shows the expected increase due to the z13 optimizations.
Thanks

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------- Comment From <email address hidden> 2023-08-03 05:17 EDT-------
The new libgmp version 6.3.0 from upstream which was included in Ubuntu 23.10 (proposed) fails with illegal instructions due to the z13 part.

Therefore, z13 optimizations had to be temporarily removed until problem is fixed.

The error has been reported by Canonical in the following separate LP entry / bugzilla:

Bug 203320 - LP#2029438 : [Reverse Mirror] gmp z13 config fails with illegal instructions

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------- Comment From <email address hidden> 2023-08-04 11:56 EDT-------
In the meantime, the error described in the separate BZ / LP
(Bug 203320 - LP#2029438 : [Reverse Mirror] gmp z13 config fails with illegal instructions)
has been fixed (thanks @Stefan)

Therefore, the z13 optimizations should now be re-included.