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From: Richard Sandiford <richard.sandiford@arm.com>
To: Robin Dapp <rdapp.gcc@gmail.com>
Mail-Followup-To: Robin Dapp <rdapp.gcc@gmail.com>,Richard Biener <rguenther@suse.de>,  gcc-patches <gcc-patches@gcc.gnu.org>,  "juzhe.zhong\@rivai.ai" <juzhe.zhong@rivai.ai>, richard.sandiford@arm.com
Cc: Richard Biener <rguenther@suse.de>,  gcc-patches <gcc-patches@gcc.gnu.org>,  "juzhe.zhong\@rivai.ai" <juzhe.zhong@rivai.ai>
Subject: Re: [PATCH] expmed: Perform mask extraction via QImode [PR112773].
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Date: Tue, 12 Dec 2023 15:32:54 +0000
In-Reply-To: <35167f65-7f43-4d76-96da-aefe2a5f5237@gmail.com> (Robin Dapp's
	message of "Tue, 12 Dec 2023 16:11:54 +0100")
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Robin Dapp <rdapp.gcc@gmail.com> writes:
>> - Change the second mode to vec_extract_optab.  This is only a name
>>   lookup, and it seems more natural to continue using the real element mode.
>
> Am I understanding correctly that this implies we should provide
> a vec_extract<bimode>bi expander?  (with the innermode being BImode
> here).

Yeah, I think so.  That way the interpretation of the mode stays in
sync with the interpretation of the bit position.  If instead we used
QImode with a bitnum of <number of elements - 1>, the top 7 bits of the
read would logically be out of bounds.

Thanks,
Richard