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Re: Arch-independent double-word clz expansion and a few other tweaks for bitscanning

From: Zack Weinberg <zack at codesourcery dot com>
To: Mark Mitchell <mark at codesourcery dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Mon, 03 Sep 2007 10:49:32 -0700
Subject: Re: Arch-independent double-word clz expansion and a few other tweaks for bitscanning
References: <46BD5B0D.403@codesourcery.com> <46CE045F.9030509@codesourcery.com>

    * optabs.c: Remove unnecessary forward declarations.
    (expand_unop_direct): New, broken out of expand_unop.
    (expand_doubleword_clz): New.
    (expand_ctz): Move above expand_ffs.  Use
    start_sequence, end_sequence, add_equal_note, and
    expand_unop_direct.  Add more commentary.
    (expand_ffs): Try both ctz optab and expand_ctz.
    Generate a test and branch if the hardware doesn't give us
    a useful value for input zero.  Style improvements similar to
    expand_ctz.

* config/arm/arm.md (ffssi2, ctzsi2): Delete.

I have committed this part, which was uncontroversial.

zw

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