March 20, Sugar 2.0 – Proposal Presented to Accellera FVTC Cindy Eisner Joint Work with Dana Fisman IBM Research Laboratory in Haifa

March 20, 2002Sugar 2.0 – Accellera Proposal2 Overview What ’ s new in Sugar 2.0 (reminder) What ’ s new since February presentation Sugar with respect to requirements Sugar advantages Summary

March 20, 2002Sugar 2.0 – Accellera Proposal3 What ’ s new in Sugar 2.0 (reminder) Sugar Foundation Language Three “ flavors ” Verilog, VHDL, EDL Four layers: boolean, temporal, modeling, verification Verification layer verification directives, statement grouping Support for multiple clocks (strong/weak) Abort operator Formal definition of finite semantics

March 20, 2002Sugar 2.0 – Accellera Proposal4 What ’ s new since February No major changes since draft presentation of last month Document proposal has been completed and fleshed out with more details Added a discussion of Sugar formulas which are checked on-the-fly VHDL flavor is left undefined at this time (but syntax has been checked so as not to conflict with VHDL boolean expressions) Two minor changes – see next slides

March 20, 2002Sugar 2.0 – Accellera Proposal5 Minor change #1 from February draft always (p -> Simplified use of multiple clocks doesn ’ t require as many parentheses clkp clkq p q

March 20, 2002Sugar 2.0 – Accellera Proposal6 Minor change #2 from February draft A module can be bound to a verification unit Meaning is that signals of the verification unit map by name to signals in the bound module Allows same specification to be used no matter how block is embedded in design Vunit can also be bound to a specific instance (requirement R50a) See example on next slide

March 20, 2002Sugar 2.0 – Accellera Proposal7 Binding a vunit vunit default { property pulsed(s) = always (s -> next !s); } vunit myunit(blocka) { assume pulsed(req_in); assert pulsed(ack_out); } vunit yourunit(blockb) { assert pulsed(req_out); assume pulsed (ack_in); }

March 20, 2002Sugar 2.0 – Accellera Proposal8 Sugar 2.0 with respect to requirements Sugar 2.0 proposal fulfills all requirements Highlights: Layered definition Three flavors Powerful sequences Multiple clocks Reset support (through “ abort ” operator) Named properties, sequences, and endpoints Formal semantics – both finite and infinite Can specify any omega-regular language

March 20, 2002Sugar 2.0 – Accellera Proposal9 Advantage 1 – History and Track Record Mature – eight years of practical experience Extensive user base Contrast with CBV which has recently undergone a major revolution

March 20, 2002Sugar 2.0 – Accellera Proposal10 Advantage 2 – Easy to learn, use A Sugar specification says what it means always ((snoop & hitm) |=> {!trans_start[*]; trans_start & writeback}) Contrast to somewhat convoluted formulation in CBV using “not” and “fail”: always if (snoop & hitm) +(1) : not [fail [!trans_start{*}; trans_start & writeback]] ;

March 20, 2002Sugar 2.0 – Accellera Proposal11 Advantage 3 – Succinct A Sugar specification is concise: forall N: 1..8: always within(write_command_start & size=N; LAST){gx_start[=N]} Contrast with verbosity of CBV: task sugar_within (r : regexp, b : bool, s : regexp) ; if (r) not [ fail [[!b{*} && s ]; b] ] ; endtask function \sugar_.[=.] (b : bool, n : nat) : regexp ; return [[!b{*};b]{n}; !b{*}] ; endfunction begin_and for (N : nat = 1; N <= 8; N = N + 1) always sugar_within ( write_command_start & (size == N), LAST, \sugar_.[=.] (gx_start, N) ) ; end

March 20, 2002Sugar 2.0 – Accellera Proposal12 Advantage 4 – Elegant formal semantics Semantics are well defined – formal semantics appear in Sugar 2.0 proposal elegant – formal semantics are only 3 pages long Contrast with lengthy semantics document of CBV

March 20, 2002Sugar 2.0 – Accellera Proposal13 Advantage 5 – Known efficient model checking algorithms Known model checking algorithms LTL and CTL model checking well-known Translation of regular expressions to automata is well-known Contrast with specialized algorithms of CBV

March 20, 2002Sugar 2.0 – Accellera Proposal14 Advantage 6 – Known efficient simulation algorithms Known algorithms for finite time reasoning: as implemented in FoCs implementation sketched in Sugar 2.0 proposal Contrast with CBV, whose implementation of the newer parts of the language is untried

March 20, 2002Sugar 2.0 – Accellera Proposal15 Advantage 7 – Declarative language Temporal layer is declarative Specification can be easily read Contrast with CBV, which mixes declarative and procedural code

March 20, 2002Sugar 2.0 – Accellera Proposal16 Advantage 8 – Expressive power Sugar Foundation Language allows the expression of any omega- regular language Optional Branching Extension allows specification of deadlock-freedom Contrast with less expressive CBV

March 20, 2002Sugar 2.0 – Accellera Proposal17 Advantage 9 – Built-in syntactic sugar Specifications are unambiguous, so can be easily read always ((snoop & hitm) -> next next_event(trans_start)(writeback)) Contrast with CBV, which requires the user to do a lot of the work: function cbv_next_event(e : bool) : regexp ; return [first_match [1{*};e]] ; endfunction always if (snoop & hitm) +(1) : if (cbv_next_event(trans_start)) writeback ;

March 20, 2002Sugar 2.0 – Accellera Proposal18 Summary Sugar is an elegant, powerful specification language with a strong track record both within and outside of IBM Sugar has existing implementations in both model checking (RuleBase) and simulation (Focs) Implementations are sketched in Sugar 2.0 proposal