[Bug rtl-optimization/34283] New: Non-optimal reload register used

[ubizjak at gmail dot com]

Following testcase:

--cut here--
typedef long long __m128i __attribute__ ((__vector_size__ (16),
__may_alias__));
typedef long long __v2di __attribute__ ((__vector_size__ (16)));


__m128i _mm_set_epi64x (long long __q1, long long __q0)
{
  return __extension__ (__m128i)(__v2di){ __q0, __q1 };
}
--cut here--

compiles using -O2 -msse2 into:

_mm_set_epi64x:
        movq    12(%esp), %xmm1
        movhps  4(%esp), %xmm1
(1)     movdqa  %xmm1, %xmm0
        ret

insn (1) is not needed.

Before reload, we have:

(insn:HI 12 7 18 2 epi.c:8 (set (reg/i:V2DI 21 xmm0 [ <result> ])
        (vec_concat:V2DI (mem/c/i:DI (plus:SI (reg/f:SI 16 argp)
                    (const_int 8 [0x8])) [2 __q0+0 S8 A32])
            (mem/c/i:DI (reg/f:SI 16 argp) [2 __q1+0 S8 A32]))) 1039
{vec_concatv2di} (nil))

(insn:HI 18 12 0 2 epi.c:8 (use (reg/i:V2DI 21 xmm0 [ <result> ])) -1 (nil))


For some reason reload isn't satisfied with %xmm0:

Reload 0: reload_in (DI) = (mem/c/i:DI (plus:SI (reg/f:SI 7 sp)
                                                        (const_int 12 [0xc]))
[2 __q0+0 S8 A32])
        reload_out (V2DI) = (reg/i:V2DI 21 xmm0 [ <result> ])
        SSE_REGS, RELOAD_OTHER (opnum = 0)
        reload_in_reg: (mem/c/i:DI (plus:SI (reg/f:SI 7 sp)
                                                        (const_int 12 [0xc]))
[2 __q0+0 S8 A32])
        reload_out_reg: (reg/i:V2DI 21 xmm0 [ <result> ])
        reload_reg_rtx: (reg:V2DI 22 xmm1)


The insn pattern is:

  [(set (match_operand:V2DI 0 "register_operand"     "=Y2,?Y2,Y2,x,x,x")
        (vec_concat:V2DI
          (match_operand:DI 1 "nonimmediate_operand" "  m,*y ,0 ,0,0,m")
          (match_operand:DI 2 "vector_move_operand"  "  C,  C,Y2,x,m,0")))]

So, reload should take into account that operand 1 should match operand 0, so
%xmm0 should be used.


-- 
           Summary: Non-optimal reload register used
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ubizjak at gmail dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34283