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Subject: [Bug rtl-optimization/106594] [13 Regression] sign-extensions no
 longer merged into addressing mode
Date: Wed, 17 Aug 2022 01:05:54 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106594

Hans-Peter Nilsson <hp at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hp at gcc dot gnu.org

--- Comment #7 from Hans-Peter Nilsson <hp at gcc dot gnu.org> ---
(In reply to Roger Sayle from comment #5)
> I'm sure if GCC instead canonicalized to the sign_extend form, that other
> targets would show similar asymmetries (it's only when things change that
> anyone notices the difference).  I'll see if I can come up with a fix over
> the weekend.

Maybe I'm hallucinating and I'm certainly late to the game, but perhaps a
REG_NONNEGATIVE note can be added on the insn for the target register when
doing the AND transformation and then combine can be improved to try to rep=
lace
ZERO_EXTEND with SIGN_EXTEND when seeing this note on the applicable input
operand?=