When generating unwind tables for code which uses return-address signing, we need to toggle the RA_SIGN_STATE DWARF register around any tail-calls, because these require the return address to be authenticated before the call, and could throw an exception. This is done using the .cfi_negate_ra_state directive before the call, and .cfi_restore_state at the start of the next basic block. However, since D153098, the .cfi_restore_state isn't being inserted, because the CFIFixup pass isn't being run. This re-enables that pass when return-adress signing is enabled. Reviewed By: ikudrin, MaskRay Differential Revision: https://reviews.llvm.org/D156428
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