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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/85730] complex code for modifying lowest byte in a
 4-byte vector
Date: Thu, 07 Oct 2021 11:51:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D85730

--- Comment #8 from Uro=C5=A1 Bizjak <ubizjak at gmail dot com> ---
Created attachment 51564
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D51564&action=3Dedit
Prototype patch

Attached patch works around reload problem and creates:

        movl    %edi, %eax
        movb    %dil, %al
        addb    %al, %al
        ret

for all cases. Please note that some follow-up pass is needed to remove
"movb %dil, %al", since preceding instruction already moves full value from
%edi to %eax, so partial move is not needed.=