Reintroduce comment

Author: Stylie777

libunwind/src/DwarfParser.hpp

@@ -808,6 +808,9 @@ bool CFI_Parser<A>::parseFDEInstructions(A &addressSpace,
             results->savedRegisters[UNW_AARCH64_RA_SIGN_STATE].value ^ 0x3;
         results->setRegisterValue(UNW_AARCH64_RA_SIGN_STATE, value,
                                   initialState);
+        // When using Feat_PAuthLR, the PC value needs to be captured so that
+        // during unwinding, the correct PC value is used for re-authentication.
+        // It is assumed that the CFI is placed before the signing instruction.
         results->ptrAuthDiversifier = fdeInfo.pcStart + codeOffset;
         _LIBUNWIND_TRACE_DWARF(
             "DW_CFA_AARCH64_negate_ra_state_with_pc(pc=0x%" PRIx64 ")\n",