[Bug target/67288] [7/8/9 regression] non optimal simple function (useless additional shift/remove/shift/add)

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67288

Jeffrey A. Law <law at redhat dot com> changed:

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                 CC|                            |law at redhat dot com

--- Comment #15 from Jeffrey A. Law <law at redhat dot com> ---
I agree that the data combine would need comes from a different block.  But
ISTM that there's a dominance relationship we could exploit here.

Specifically blocks 2 & 3 are a class extended basic block.  Information
generated in bb2 (or on the edge bb2->bb3) may still be available in bb3.

I don't think we're set up to exploit extended blocks in combine, but that may
be something worth exploring.