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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/78103] Failure to optimize with __builtin_clzl
Date: Tue, 27 Jul 2021 08:52:43 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D78103

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #51204|0                           |1
        is obsolete|                            |

--- Comment #16 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51209
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D51209&action=3Dedit
gcc12-pr78103.patch

Updated patch.  This one fixes the reuse of a pseudo you've mentioned above,
and fixes gcc.target/i386/pr101175.c regression the patch reintroduced by
adding !TARGET_LZCNT conditions to the two new define_insns.

Nothing changes for combine though, I think it really would be nice if it c=
ould
either change newly added pseudos from combine_split_insns by i2dest if
possible, or better handle new pseudos from both combine_split_insns and wh=
en
for find_split_point i2dest can't be resued with creating LOG_LINKS.

I guess I can work around this by using define_insn_and_split instead of a
combiner splitter, but combine splitters are cleaner...=