public inbox for
 help / color / mirror / Atom feed
From: Robin Dapp <>
To: "H.J. Lu" <>
Cc: Jeff Law <>,
Subject: Re: [RFC] postreload cse'ing vector constants
Date: Wed, 28 Sep 2022 18:48:05 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

> I opened:

The online docs for encodekey256 also say

XMM4 through XMM6 are reserved for future usages and software should not
rely upon them being zeroed.

I believe we also zero there.

> This sounds like an issue.

So with your patch for encodekey128 the regression is gone and we zero
(pxor) xmm0 in both versions.  The case I outlined before does not
actually happen since cprop_hardreg propagates the (newly) zeroed
register to the use sites rather than zeroing every time.

I guess this just leaves the situation where we implicitly know that a
reg is zero and by rather zeroing another one we miss the cprop_hardreg
opportunity.  Not sure how common this is and if it's a blocker for this
patch.  No regressions on x86, aarch64, power9 and s390 now.  Most
likely we don't check to that granularity in the test suite and even
here it was more of accidental hit.

  reply	other threads:[~2022-09-28 16:48 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-07 14:40 Robin Dapp
2022-09-07 15:06 ` Jeff Law
2022-09-07 15:33   ` Robin Dapp
2022-09-07 15:49     ` Jeff Law
2022-09-08 13:04       ` Robin Dapp
2022-09-27 17:40         ` Robin Dapp
2022-09-27 19:39           ` H.J. Lu
2022-09-28 16:48             ` Robin Dapp [this message]
2022-11-03 12:38               ` Robin Dapp
2022-11-20 16:40                 ` Jeff Law

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-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \

* 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;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).