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Date: Thu, 14 Apr 2005 01:39:00 -0000
From: "anton at samba dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Message-ID: <20050414013914.21017.anton@samba.org>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug c/21017] New: ppc 64bit target not using rlwinm
X-Bugzilla-Reason: CC
X-SW-Source: 2005-04/txt/msg01860.txt.bz2
List-Id: <gcc-bugs.sourceware.org>

Using a recent 4.0 CVS:

gcc version 4.0.0 20050412 (prerelease)

Compiling the following as 64bit:

unsigned int foo(unsigned int x)
{
                return ((x >> 16) & 0xffff) | ((x & 0xffff) << 16);
}

Results in:

.L.foo:
        slwi 0,3,16
        srwi 3,3,16
        or 3,3,0
        rldicl 3,3,0,32
        blr

Compiling for 32bit results in:

foo:
        rlwinm 3,3,16,0xffffffff
        blr

It looks like the 64bit case could be done in 2 instructions if we masked the
top 32bits of the rlwinm result.

-- 
           Summary: ppc 64bit target not using rlwinm
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anton at samba dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21017