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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: enter image description here

in code I implemented it like this:insn.Op1.addr = insn.ea + (((code32 & 0x3FFFFFF) << 1) & 0x3FFFFFF);

enter image description here

but I don’t understand what sign_extend does ?

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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.

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  • that is, if 26 bits are 0, then we set bits 31..26 to 0, otherwise to 1? or force set to 1 - sign_extend, to 0 - zero_extend?
    – Andynvkz
    Mar 7 at 7:25
  • If the most significant bit is 1 - all additional higher bits are set to 1. Otherwise - 0. signed, (int8) 0xFF equals to decimal-1. To keep the value in 32 bit they have to be all 1s, i.e. 0xFFFFFFFF
    – Yotamz
    Mar 7 at 8:43

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