Jit_LoadStore: Minor dcbx register optimization

Instructions referencing registers r8-r15 take an additional byte to
encode. `reg_downcount` may be assigned to one of these registers, so it
is a small size win to store the downcount value in `RSCRATCH` first.

Before:
33 D2                xor         edx,edx
44 8B 6D 64          mov         r13d,dword ptr [rbp+64h]
45 85 ED             test        r13d,r13d
7E 30                jle         0000023546B43F6D
44 8B B5 D4 02 00 00 mov         r14d,dword ptr [rbp+2D4h]
41 8B C5             mov         eax,r13d
BF 07 00 00 00       mov         edi,7
F7 F7                div         eax,edi

After:
33 D2                xor         edx,edx
8B 45 64             mov         eax,dword ptr [rbp+64h]
85 C0                test        eax,eax
7E 30                jle         000001AFBBAE359D
44 8B B5 D4 02 00 00 mov         r14d,dword ptr [rbp+2D4h]
44 8B E8             mov         r13d,eax
BF 07 00 00 00       mov         edi,7
F7 F7                div         eax,edi

0 files changed, 0 insertions, 0 deletions