From: "Marvin Häuser" <mhaeuser@posteo.de>
To: "S, Ashraf Ali" <ashraf.ali.s@intel.com>
Cc: devel@edk2.groups.io, chasel.chiu@intel.com,
Nate DeSimone <nathaniel.l.desimone@intel.com>,
star.zeng@intel.com
Subject: Re: [edk2-devel] [PATCH v2] IntelFsp2Pkg: Fix NASM X64 build warnings.
Date: Sun, 19 Mar 2023 09:36:56 +0000 [thread overview]
Message-ID: <E4601C5E-4189-4AB1-B3E1-688B80C72269@posteo.de> (raw)
In-Reply-To: <DM4PR11MB52805F21FC419FEEE9780CD8D7839@DM4PR11MB5280.namprd11.prod.outlook.com>
[-- Attachment #1: Type: text/plain, Size: 906 bytes --]
Yes - it does. Most (if not all?) operations on 32-bit registers zero-extend the corresponding 64-bit register. This is an AMD64 / Intel 64 design to combat partial register stall. Please consult the SDM (or at least try it out).
What I didn’t realize is that “mov eax, eax” apparently defeats register renaming optimisations: https://stackoverflow.com/a/45660140
Best regards,
Marvin
> On 19. Mar 2023, at 10:07, S, Ashraf Ali <ashraf.ali.s@intel.com> wrote:
>
> Hi.,
>
> Nope, it will not clear the upper 32bit right.
>
>
> From: Marvin Häuser <mhaeuser@posteo.de>
> Sent: Sunday, March 19, 2023 3:38 AM
> To: S, Ashraf Ali <ashraf.ali.s@intel.com>; devel@edk2.groups.io
> Subject: Re: [edk2-devel] [PATCH v2] IntelFsp2Pkg: Fix NASM X64 build warnings.
>
> Hi Ashraf,
>
> ”mov eax, eax” does clear the high 32 Bits of rax.
>
> Best regards,
> Marvin
[-- Attachment #2: Type: text/html, Size: 2722 bytes --]
next prev parent reply other threads:[~2023-03-19 9:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-17 17:20 [PATCH v2] IntelFsp2Pkg: Fix NASM X64 build warnings Chiu, Chasel
2023-03-18 13:04 ` [edk2-devel] " Ashraf Ali S
2023-03-18 22:07 ` Marvin Häuser
2023-03-19 9:07 ` Ashraf Ali S
2023-03-19 9:36 ` Marvin Häuser [this message]
2023-03-19 16:57 ` Ashraf Ali S
2023-03-18 22:06 ` Marvin Häuser
2023-03-20 6:03 ` Ni, Ray
2023-03-20 7:31 ` Pedro Falcato
2023-03-21 23:05 ` Nate DeSimone
2023-03-22 0:17 ` Chiu, Chasel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-list from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=E4601C5E-4189-4AB1-B3E1-688B80C72269@posteo.de \
--to=devel@edk2.groups.io \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox