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[dv/formal] Helpers for DivInstrStable

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To make the proof of DivInstrStable, this commit adds two helper
properties in the previous step. One that when an instruction is not a
multiply that the multiplier state must never leave ALBL and one that
the writeback stage must have a valid instruction in it if it is
blocking an instruction from proceeding from EX to WB. This allow
DivInstrStable to be proven with Hp 2.
This commit is contained in:
Marno van der Maas 2025-05-09 16:22:44 +01:00 • committed by Harry Callahan
parent 4fe6b7d53f
commit 0b718c5eac
1 changed files with 25 additions and 20 deletions
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7
dv/formal/thm/ibex.proof
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@ -219,6 +219,11 @@ lemma ibex
MultEndState: have (instr_will_progress |=> `MULTG.mult_state_q == `MULTG.ALBL) MultEndState: have (instr_will_progress |=> `MULTG.mult_state_q == `MULTG.ALBL)
# Assert that only when multiplying the mult_state_q leaves ALBL mode. This assertion helps remove some state space for DivInstrStable.
DivInstrNotMult: have (~`MULT.mult_en_internal |-> `MULTG.mult_state_q == `MULTG.ALBL)
# When there is an instruction is finished in EX but is blocked from moving to WB then there must be a valid instruction in the WB stage. This is a helper property for DivInstrStable
InstrInWbStage: have (wbexc_exists & ~wbexc_finishing -> `WBG.wb_valid_q)
/ /
MemErrKind: have (finishing_executed && wbexc_is_mem_instr && ~wbexc_illegal && wbexc_err |-> `IDC.store_err_q | `IDC.load_err_q) MemErrKind: have (finishing_executed && wbexc_is_mem_instr && ~wbexc_illegal && wbexc_err |-> `IDC.store_err_q | `IDC.load_err_q)
@ -255,7 +260,7 @@ lemma ibex
FirstCycleNoGnt: have (`ID.instr_first_cycle |-> ~mem_gnt_fst_q) FirstCycleNoGnt: have (`ID.instr_first_cycle |-> ~mem_gnt_fst_q)
MemStartFirstCycle: have (`LSU.ls_fsm_cs == `LSU.IDLE && `CR.lsu_req |-> `ID.instr_first_cycle) MemStartFirstCycle: have (`LSU.ls_fsm_cs == `LSU.IDLE && `CR.lsu_req |-> `ID.instr_first_cycle)
# The below is slow!
DivInstrStable: have (`MULT.md_state_q != `MULT.MD_IDLE |-> $stable(`CR.instr_rdata_id) && `CR.instr_valid_id && (~`ID.stall_multdiv -> `MULT.md_state_q == `MULT.MD_FINISH) && `MULTG.mult_state_q == `MULTG.ALBL && `MULT.div_en_internal && (~wbexc_exists | wbexc_finishing)) DivInstrStable: have (`MULT.md_state_q != `MULT.MD_IDLE |-> $stable(`CR.instr_rdata_id) && `CR.instr_valid_id && (~`ID.stall_multdiv -> `MULT.md_state_q == `MULT.MD_FINISH) && `MULTG.mult_state_q == `MULTG.ALBL && `MULT.div_en_internal && (~wbexc_exists | wbexc_finishing))
InstrReqCount: have ( InstrReqCount: have (