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During InsertNegateRAState pass we check the annotations on instructions, to decide where to generate the OpNegateRAState CFIs in the output binary. As only instructions in the input binary were annotated, we have to make a judgement on instructions generated by other BOLT passes. Incorrect placement may cause issues when an (async) unwind request is received during the new "unknown" instructions. This patch adds more logic to make a more informed decision on by taking into account: - unknown instructions in a BasicBlock with other instruction have the same RAState. Previously, if the BasicBlock started with an unknown instruction, the RAState was copied from the preceding block. Now, the RAState is copied from the succeeding instructions in the same block. - Some BasicBlocks may only contain instructions with unknown RAState, As explained in issue #160989, these blocks already have incorrect unwind info. Because of this, the last known RAState based on the layout order is copied. Updated bolt/docs/PacRetDesign.md to reflect changes.