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From: "amodra at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/67328] range test rather than single bit test for code testing enum values
Date: Tue, 25 Aug 2015 13:09:00 -0000	[thread overview]
Message-ID: <bug-67328-4-5qQf7Py4aX@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-67328-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67328

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW

--- Comment #3 from Alan Modra <amodra at gmail dot com> ---
Maybe adding #if ALT only confused the issue.  For -UALT -O1 on x86_64 I get

test_pic:
        testb   $1, (%rdi)
        je      .L1
        addl    $1, result(%rip)
.L1:
        rep ret

test_exe:
        movzbl  (%rdi), %eax
        andl    $3, %eax
        cmpb    $1, %al
        ja      .L3
        addl    $1, result(%rip)
.L3:
        rep ret

For test_exe I would like to see the following equivalent and better optimised
code.

test_exe:
        testb   $2, (%rdi)
        jne     .L3
        addl    $1, result(%rip)
.L3:
        rep ret

The optimisation to a bit test for test_pic happens in reassoc1, or at least
that's where the process starts.


      parent reply	other threads:[~2015-08-25 13:09 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-08-23 13:41 [Bug tree-optimization/67328] New: " amodra at gmail dot com
2015-08-23 13:45 ` [Bug tree-optimization/67328] " amodra at gmail dot com
2015-08-25  8:38 ` rguenth at gcc dot gnu.org
2015-08-25 13:09 ` amodra at gmail dot com [this message]

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