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From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/82940] Suboptimal code for (a & 0x7f) | (b & 0x80) on powerpc
Date: Mon, 23 Aug 2021 15:45:40 +0000 [thread overview]
Message-ID: <bug-82940-4-bVRUKW1Pwr@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-82940-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82940
--- Comment #8 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #7)
> (In reply to Peter Cordes from comment #6)
> > # power64 GCC 9.2.1 (ATI13.0)
> > rlwimi 3,4,0,255 # bit-blend according to mask, rotate count=0
> > rldicl 3,3,0,32 # Is this zero-extension to 64-bit redundant?
>
> It is: the rlwinm does an AND with 0xff already, so that clears the top 32
> bits for sure.
Wow I cannot read, it is an rlwimi, so scratch that.
The rlwimi here keeps the top 56 bits intact, and they already were 0, so the
insn still is redundant.
next prev parent reply other threads:[~2021-08-23 15:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-82940-4@http.gcc.gnu.org/bugzilla/>
2021-08-01 7:16 ` pinskia at gcc dot gnu.org
2021-08-01 9:57 ` segher at gcc dot gnu.org
2021-08-22 22:16 ` peter at cordes dot ca
2021-08-23 15:40 ` segher at gcc dot gnu.org
2021-08-23 15:45 ` segher at gcc dot gnu.org [this message]
2023-04-11 17:05 ` aagarwa at gcc dot gnu.org
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