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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102943] [12 Regression] Jump threader
 compile-time hog with 521.wrf_r
Date: Tue, 02 Nov 2021 07:29:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102943

--- Comment #9 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #8)
> The 'tree VRP threader' instances are now gone (well, obviously..).  Ther=
e's
> now
>=20
>  backwards jump threading           :  15.98 ( 13%)=20
>  TOTAL                              : 120.33=20=20=20=20=20
>=20
>  backwards jump threading           :  41.23 ( 33%)=20
>  TOTAL                              : 125.43=20=20=20=20=20=20=20=20=20
>=20
>  backwards jump threading           :  89.97 ( 19%)=20=20
>  TOTAL                              : 473.55=20=20=20=20=20
>=20
> in the three biggest LTRANS units (all others are <10s compile time).  It
> might
> be that the VRP threading opportunities are now simply taken by backwards
> threader instances.

Correct.  There's is no longer a post-VRP threader based on the forward
threader.  Now there's just one pre-VRP based on the backward threader.

Thanks for re-confirming.  I have hunted down a copy of SPEC2017 and will be
looking at this today.  If anyone has specific configury tricks/options for
SPEC, please mail me privately, as it's been decades since I last ran SPEC.=