PowerPC instructions andcx and orcx complement the value of register b
before performing their respective bitwise operation. If this register
happens to contain a known value, we can precompute the complement,
allowing us to generate simpler code.
- andcx
Before:
BF 00 01 00 00 mov edi,100h
F7 D7 not edi
41 23 FE and edi,r14d
After:
41 8B FE mov edi,r14d
81 E7 FF FE FF FF and edi,0FFFFFEFFh
- orc
Before:
41 BE 04 00 00 00 mov r14d,4
41 F7 D6 not r14d
45 0B F5 or r14d,r13d
After:
45 8B F5 mov r14d,r13d
41 83 CE FB or r14d,0FFFFFFFBh
26f70657bc