[Bug target/20781] New: 64 bit shift by non-constant implemented as libcall on PPC32

["dberlin at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

given something like:
long long foo(long long X, unsigned int Y) { return X << Y; }
or
long long foo(long long X, unsigned int Y) { return X >> Y; }

We currently generate a libcall to do the shift in 32 bit ppc.

On the contrary, XLC will *always* expand these shifts to an instruction
sequence (LLVM now does the same as of a few days ago), rather than a library call.

The first will generate with xlc -O3 -qarch=ppc970
.foo:
        rlwinm  r0,r5,25,0,6
        subfic  r6,r5,32
        slw     r3,r3,r5
        addi    r7,r5,-32
        srw     r6,r4,r6
        xoris   r0,r0,0x8000
        slw     r7,r4,r7
        slw     r4,r4,r5
        or      r5,r6,r7
        srawi   r0,r0,31
        or      r3,r3,r5
        and     r4,r0,r4
        and     r3,r0,r3

and the second:
.foo:
        subfic  r0,r5,32
        addi    r8,r5,-32
        rlwinm  r6,r5,26,0,0
        rlwinm  r7,r5,25,0,6
        srw     r8,r3,r8
        slw     r9,r3,r0
        xoris   r7,r7,0x8000
        srw     r0,r4,r5
        and     r4,r3,r6
        or      r9,r9,r8
        or      r0,r0,r9
        srawi   r6,r7,31
        srawi   r8,r3,31
        rlwinm  r7,r5,0,27,31
        sraw    r4,r4,r7
        sraw    r3,r3,r5
        or      r0,r0,r4
        andc    r5,r8,r6
        and     r3,r6,r3
        and     r0,r6,r0
        or      r4,r5,r0
        or      r3,r5,r3

(O5 will give slightly better code for both, but let's start somewhere :P)

-- 
           Summary: 64 bit shift by non-constant implemented as libcall on
                    PPC32
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dberlin at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc-linux
  GCC host triplet: powerpc-linux
GCC target triplet: powerpc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20781