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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/113910] [12/13 Regression] Factor 15 slowdown
 compiling AMDGPUDisassembler.cpp on SPARC
Date: Thu, 21 Mar 2024 11:49:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113910

--- Comment #18 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:9a19811ea1e9b3024c0f41b074d71679088bb2d7

commit r13-8478-g9a19811ea1e9b3024c0f41b074d71679088bb2d7
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Feb 14 12:33:13 2024 +0100

    tree-optimization/113910 - huge compile time during PTA

    For the testcase in PR113910 we spend a lot of time in PTA comparing
    bitmaps for looking up equivalence class members.  This points to
    the very weak bitmap_hash function which effectively hashes set
    and a subset of not set bits.

    The major problem with it is that it simply truncates the
    BITMAP_WORD sized intermediate hash to hashval_t which is
    unsigned int, effectively not hashing half of the bits.

    This reduces the compile-time for the testcase from tens of minutes
    to 42 seconds and PTA time from 99% to 46%.

            PR tree-optimization/113910
            * bitmap.cc (bitmap_hash): Mix the full element "hash" to
            the hashval_t hash.

    (cherry picked from commit ad7a365aaccecd23ea287c7faaab9c7bd50b944a)=