Formality：对含有FF的设计做Formality，为什么都报FF failing

做了几个时序电路的formality，发现都是FF failing，找不出什么原因，请前辈帮忙，谢谢
设置：
1 ##
2 set hdlin_ignore_full_case true
3 set hdlin_ignore_parallel_case false
4 set hdlin_warn_on_mismatch_message "FMR_ELAB-147"
5 set hdlin_error_on_mismatch_message true
6 set hdlin_unresolved_modules black_box
7 set hdlin_enable_hier_naming true
8 set verification_set_undriven_signals X
9 set verification_constant_prop_mode auto
10 man enable_multiplier_generation

======================================================================
1179Compare point 269/FFY/ASYNC_FF failed (is not equivalent)
1180Compare point 147/FFX/ASYNC_FF failed (is not equivalent)
1181Compare point 298/FFY/ASYNC_FF failed (is not equivalent)
1182Compare point 299/FFY/ASYNC_FF failed (is not equivalent)
1183Compare point 300/FFY/ASYNC_FF failed (is not equivalent)
1184Compare point 301/FFY/ASYNC_FF failed (is not equivalent)
1185Compare point 291/FFY/ASYNC_FF failed (is not equivalent)
1186Compare point 302/FFY/ASYNC_FF failed (is not equivalent)
1187
1188 ********************************* Verification Results *********************************
1189 Verification FAILED
1190 -------------------
1191Reference design: r:/WORK/divider_dshift
1192Implementation design: i:/WORK/divider_dshift
1193590 Passing compare points
119420 Failing compare points
11950 Aborted compare points
119672 Unverified compare points
1197 ----------------------------------------------------------------------------------------
1198 Matched Compare PointsBBPinLoopBBNetCutPortDFFLATTOTAL
1199 ----------------------------------------------------------------------------------------
1200 Passing (equivalent)260000652650590
1201 Failing (not equivalent)0000020020
1202 Unverified0000072072
1203 ****************************************************************************************

FF是什么东西?

FF 就是DFF，谢谢