[Bug rtl-optimization/33790] New: postreload can handle the case where the memory locations use different modes

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

Take the following testcase (either on spu-elf or powerpc-linux-gnu with
-maltivec):
#define vector __attribute__((__vector_size__(16) ))

typedef vector float vec_float4;
typedef struct {
        vec_float4 data;
} VecFloat4;

typedef struct {
        vec_float4 a;
        vec_float4 b;
} VecFloat4x2;


VecFloat4 test1(VecFloat4 a, VecFloat4 b)
{
        a.data = a.data+b.data;
        return a;
}


VecFloat4x2 test2(VecFloat4x2 data)
{
        data.a = data.a+data.a;
        data.b = data.b+data.b;
        return data;
}

----- cut -----
Right now we do (for spu-elf, it is a similar issue for PPC):
_Z5test211VecFloat4x2:
        hbr     .L5,$lr
        stqd    $sp,-128($sp)
        ai      $sp,$sp,-128
        stqd    $3,64($sp)
        stqd    $4,80($sp)
        lqd     $5,80($sp)
        lqd     $4,64($sp)
        fa      $2,$5,$5
        fa      $3,$4,$4
        stqd    $2,48($sp)
        stqd    $3,32($sp)
        lqd     $4,48($sp)
        lqd     $3,32($sp)
        ai      $sp,$sp,128
.L5:
        bi      $lr

---- cut ----
With the patch which I will attach, we get:
_Z5test211VecFloat4x2:
        fa      $2,$3,$3
        hbr     .L5,$lr
        stqd    $sp,-128($sp)
        ai      $sp,$sp,-128
        nop     127
        stqd    $3,64($sp)
        fa      $3,$4,$4
        stqd    $4,80($sp)
        nop     127
        stqd    $2,32($sp)
        ori     $4,$3,0
        stqd    $3,48($sp)
        ori     $3,$2,0
        ai      $sp,$sp,128
.L5:
        bi      $lr


----------- cut ------
Notice how the loads are gone.
Note dse could do the same.


-- 
           Summary: postreload can handle the case where the memory
                    locations use different modes
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33790