I’m writing a C-SKY (CK803S) processor module for IDA Pro, and a question arose about offsets in transitions, small ones are fine, but long ones lead to nowhere, from the documentation:
in code I implemented it like this:insn.Op1.addr = insn.ea + (((code32 & 0x3FFFFFF) << 1) & 0x3FFFFFF);
but I don’t understand what sign_extend does ?
Signextend is expanding an integer of some size into a larger size and filling the extra bits with the original sign bit. In other words - keeping the larger int positive/negative.
Example:
An original 8-bit number 0x7F (Binary 01111111) signextended to 32 bit becomes 0x0000007F.
An original 8-bit number 0x80 (Binary 10000000) signextended to 32 bit becomes 0xFFFFFF80
It makes sense using this operation in offsets as a relative offset can be negative.
(int8) 0xFF equals to decimal-1. To keep the value in 32 bit they have to be all 1s, i.e. 0xFFFFFFFF