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Subject: [Bug middle-end/105638] Redundant stores aren't removed by DSE
Date: Wed, 01 Jun 2022 21:23:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105638

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@gcc.gnu.org>:

https://gcc.gnu.org/g:a743a72714fc4a9d7036d28d0cacdf2a3621f629

commit r13-921-ga743a72714fc4a9d7036d28d0cacdf2a3621f629
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed May 18 13:00:47 2022 -0700

    DSE: Use the constant store source if possible

    RTL DSE tracks redundant constant stores within a basic block.  When RTL
    loop invariant motion hoists a constant initialization out of the loop
    into a separate basic block, the constant store value becomes unknown
    within the original basic block.  When recording store for RTL DSE, che=
ck
    if the source register is set only once to a constant by a non-partial
    unconditional load.  If yes, record the constant as the constant store
    source.  It eliminates unrolled zero stores after memset 0 in a loop
    where a vector register is used as the zero store source.

    gcc/

            PR rtl-optimization/105638
            * df-core.cc (df_find_single_def_src): Moved and renamed from
            find_single_def_src in loop-iv.cc.  Change the argument to rtx
            and use rtx_equal_p.  Return null for partial or conditional
            defs.
            * df.h (df_find_single_def_src): New prototype.
            * dse.cc (record_store): Use the constant source if the source
            register is set only once.
            * loop-iv.cc (find_single_def_src): Moved to df-core.cc.
            (replace_single_def_regs): Replace find_single_def_src with
            df_find_single_def_src.

    gcc/testsuite/

            PR rtl-optimization/105638
            * g++.target/i386/pr105638.C: New test.=