In file PPCBranchSelector.cpp we tend to over estimate code size due to large alignment and
inline assembly. Usually it causes larger computed branch offset, it is not big problem.
But sometimes it may also causes smaller computed branch offset
than actual branch offset. If the offset is close to the limit of
encoding, it may cause problem at run time.
Following is a simplified example.
actual estimated address address ... bne Far 100 10c .p2align 4 Near: 110 110 ... Far: 8108 8108 Actual offset: 0x8108 - 0x100 = 0x8008 Computed offset: 0x8108 - 0x10c = 0x7ffc
The computed offset is at most ((1 << alignment) - 4) bytes smaller
than actual offset. So we add this number to the offset for safety.