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From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/105219] [12 Regression] SVE: Wrong code with -O3
 -msve-vector-bits=128 -mtune=thunderx
Date: Tue, 12 Apr 2022 11:36:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105219

--- Comment #7 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
I have managed to find the commit where this starts failing:

commit 61fc5e098e76c9809f35f449a70c9c8d74773d9d (HEAD)
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Feb 18 11:34:52 2022 +0100

    tree-optimization/104582 - Simplify vectorizer cost API and fixes

    This simplifies the vectorizer cost API by providing overloads
    to add_stmt_cost and record_stmt_cost suitable for scalar stmt
    and branch stmt costing which do not need information like
    a vector type or alignment.  It also fixes two mistakes where
    costs for versioning tests were recorded as vector stmt rather
    than scalar stmt.

    This is a first patch to simplify the actual fix for PR104582.

    2022-02-18  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/104582
            * tree-vectorizer.h (add_stmt_cost): New overload.
            (record_stmt_cost): Likewise.
            * tree-vect-loop.cc (vect_compute_single_scalar_iteration_cost):
            Use add_stmt_costs.
            (vect_get_known_peeling_cost): Use new overloads.
            (vect_estimate_min_profitable_iters): Likewise.  Consistently
            use scalar_stmt for costing versioning checks.
            * tree-vect-stmts.cc (record_stmt_cost): New overload.

but I think this just exposes the issue.  The weird thing is while this does
change the cost calculations during vect the final vectorized code is exact=
ly
the same out of both version.=20

and indeed there's no change at all in the dumps until cunrolli, which in o=
ne
version unrolls more than the other, but I think that's just costing
difference. So I'm disabling it to continue seeing at which pass there's
actually codegen difference between these two commits.=