"xordi3" pattern in arm.md

[Philip Blundell <philb at gnu dot org>]

What purpose does this pattern serve?  It just performs splitting, and a test 
case like the one below seems to produce rather better code without it.

void g (unsigned long long);
f(unsigned long long l)
{ g(l ^ 0x1000000010000000ULL); }

compare:

f:
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, current_function_anonymous_args = 0
        stmfd   sp!, {r4, lr}
        adr     r3, .L2
        ldmia   r3, {r3-r4}
        eor     r0, r0, r3
        eor     r1, r1, r4
        @ Sibcall epilogue
        ldmfd   sp!, {r4, lr}
        b       g
.L3:
        .align  2
.L2:
        .word   268435456
        .word   268435456

and:

f:
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, current_function_anonymous_args = 0
        str     lr, [sp, #-4]!
        eor     r0, r0, #268435456
        eor     r1, r1, #268435456
        @ Sibcall epilogue
        ldr     lr, [sp], #4
        b       g

p.