Synopsys, Inc.

Altera Corporation

Robert L Walker

Mahesh A Iyer

James Beausang

Vasudeva M Kamath

Chris Ellingham

Markus F Robinson

Kenneth Wagner

Amir H Mottaez

Sanjay Dhar

Prashant Saxena

Harbinder Singh

Denis Martin

Sudipto Kundu

Kok Kiong Lee

Kenneth E Scott

Srinivas Ajjarapu

Sanjay V Kumar

Mark D Noll

Configuration data for an integrated circuit may be generated using logic design equipment to implement a logic design on the integrated circuit. The equipment may perform multiple rounds of incremental physical synthesis, incremental timing analysis, and incremental legalization operations. Each round may involve performing multiple different physical synthesis transforms on the design that are individually rejected until transforms that satisfy legality constraints and improve timing for the logic design are found and incorporated into the netlist. The configuration data may then be generated using the netlist. In this way, the logic design may be incrementally altered and verified during the physical synthesis process. This prevents the need for rejecting or accepting an entire batch logic changes to the netlist even when only some of the changes are non-ideal, thus optimizing circuit performance as well as the compile time required to implement the logic design on the integrated circuit.

Methods for incremental circuit physical synthesis

Configuration data for an integrated circuit may be generated using logic design equipment to implement a logic design on the integrated circuit. The equipment may perform incremental physical synthesis, timing optimization, and legalization operations on the logic design. The equipment may identify timing and legalization constraints and logic blocks that fail the timing constraints, and may determine whether modifying and/or moving the blocks to new locations satisfy the legalization constraints while improving the timing of the design. If the legalization constraints are not satisfied, the design equipment may recursively move non-critical logic blocks to new locations while ensuring that the legalization and timing constraints are satisfied for each move such that the timing of the design is improved. This may be repeated in multiple rounds of adjustment. A netlist may be generated after the moves are performed. The configuration data may be generated based on the netlist.

Methods for incremental circuit design legalization during physical synthesis

A computer-implemented method includes performing retiming using a circuit design to determine a retimed variation to the circuit design. The circuit design includes a first set of registers with defined power-up states and the variations each comprise a second set of registers that correspond to the first set of registers. The method includes maintaining fixed power-up states for the second set of registers in the variations. The fixed power-up states for the second set of registers are equivalent to the defined power-up states of the first set of registers. The method includes identifying registers of the second set of registers involved in an initial state conflict, and performing a mitigating action to resolve the initial state conflict to enable retiming to continue while maintaining functionally equivalent behavior as the circuit design. Various choices of initial states are also explored during retiming to increase the effect of retiming.

Retiming with fixed power-up states

A computer-implemented includes performing retiming using a circuit design to determine variation to the circuit design. The circuit design includes a first set of registers with defined power-up states and the variations each comprise a second set of registers that correspond to the first set of registers. The method includes computing and maintaining programmable power-up states for the second set of registers in the variations. The programmable power-up states computed for the second set of registers are equivalent to the defined power-up states of the first set of registers. The method includes identifying registers of the second set of registers involved in an initial state conflict, and performing a mitigating action to resolve the initial state conflict to enable retiming to continue while maintaining functionally equivalent behavior as the circuit design. Various choices of initial states are also explored during retiming to maximize the effect of retiming.

Retiming with programmable power-up states

An integrated circuit design may include registers and combinational logic. Integrated circuit design computing equipment may perform register retiming in the circuit design, whereby registers are moved across one or more portions of the combinational logic. The candidate registers to be retimed may have a different number or different types of secondary signals. In such scenarios, a selective modeling operation may be performed according to a predetermined precedence scheme to remove and model the differing secondary signals, thereby producing comparable registers with the same number and type of secondary signals. The comparable registers can then be retimed across the corresponding combinational logic. Backward or forward retiming operations may be performed in this way to achieve optimal circuit performance. During retiming adjacent combinational logic may also be combined to help minimize circuit area.

Integrated circuit retiming with selective modeling of flip-flop secondary signals

Systems and techniques are described for performing buffer tree synthesis. Some embodiments create a lookup table based on information contained in a cell library. The lookup table is then used during buffer tree synthesis.

Look-up based buffer tree synthesis

Systems and techniques for optimizing a circuit design are described. Some embodiments reduce the number of gates in the library (e.g., by dynamically pruning the library) which are considered for optimization. Some embodiments create a linear delay model, and use the linear delay model instead of a non-linear delay model to substantially reduce the amount of computation required to check whether or not a particular replacement gate improves one or more metrics of the circuit design. Some embodiments determine an order for processing the gates in the library or for processing input pins of a gate to facilitate early rejection of a candidate gate in the library of gates. In some embodiments, the evaluation of the impact of a candidate gate transformation is done progressively and level-by-level only up to the point where the gate transformation degrades one or more metrics.

Progressive circuit evaluation for circuit optimization

Systems and techniques for optimizing a circuit design are described. When a selected gate is transformed during optimization, it causes a slack value at a pin of the transformed gate to change. The change in the slack value, called the delta-slack, is then propagated through a transitive fanin cone and a transitive fanout cone of the transformed gate to compute the new slack values at all the affected pins of the design. Some embodiments update slack values without propagating arrival and required times, and also without repeatedly evaluating timing arcs to compute gate delays. The updated slack values can be used to compute timing metrics. The timing metrics can be used to decide whether or not to commit the gate transformation to the circuit design.

Delta-slack propagation for circuit optimization

Some embodiments provide a system that facilitates the creation of a design in an electronic design automation (EDA) application. During operation, the system determines a processing order for processing a set of cells in the design. In some embodiments, the processing order can be a reverse-levelized processing order. Next, the system may select a cell for performing area recovery according to the processing order. The system may then tentatively perform an area-recovery operation on the selected cell. Next, the system may determine a zone around the selected cell. Next, the system may propagate arrival times within the zone to obtain updated slack values at endpoints of the zone. The system may compute one or more timing metrics at the endpoints. If the updated slack values do not degrade the timing metric(s) at the endpoints, the system may accept the area-recovery operation of the selected cell.

Zone-based area recovery in electronic design automation

Some embodiments of the present invention provide techniques and systems for efficiently optimizing a circuit design for one or more multi-mode multi-corner (MCMM) scenarios. A system can select an optimizing transformation for a logic gate, which if applied to the logic gate, does not degrade a timing metric in a local context of the logic gate. Next, the system can determine whether applying the optimizing transformation to the logic gate degrades the timing metric in a zone around the logic gate. If so, the system can reject the optimizing transformation. Otherwise, the system can determine whether applying the optimizing transformation to the logic gate degrades the timing metric in the circuit design. If so, the system can reject the optimizing transformation. Otherwise, the system can accept the optimizing transformation.

Zone-based optimization framework for performing timing and design rule optimization

Some embodiments provide techniques and systems for improving the efficiency of area recovery in an electronic design automation (EDA) flow. During operation, the system determines a utilization of a region from a set of regions in a design floorplan. Next, the system performs area recovery (e.g., by using a processor) on the region based at least on the utilization. Specifically, the system can overlay the design floorplan with a grid, wherein the grid comprises a set of grid cells and uses the grid cells as the set of regions. The grid can be associated with a predetermined number of rows and a predetermined number of columns. The system can determine the utilization of the region by calculating the utilization as a cell area of the region divided by a placement area of the region. The utilization can be incrementally calculated during the creation and optimization of the design.

Density-based area recovery in electronic design automation

A computer implemented process and system for electronic design automation (EDA) using groups of multiple cells having loop-back connections for modeling port electrical characteristics. Multi-bit cells have multiple gates of the same function implemented within a same cell. Multi-bit components have multiple multi-bit cells implemented within a same component. Scannable multi-bit cells and components are similar to multi-bit cells and components but contain scannable sequential elements with scan chains installed. Multi-bit cells may or may not have each sequential cells' input and each sequential cells' output available externally. The scannable sequential elements of a multi-bit component are ordered into a predefined scan chain which is defined by the library containing the multi-bit component or multi-bit cell. During scan replacement processes of the EDA compile process, multi-bit cells and components of the netlist are replaced with scannable multi-bit cells and components. Also, during optimization, multi-bit cells and components undergo equivalence replacement to meet specified constraints (e.g., area, performance, etc.). To model the electrical characteristics of the port during certain optimizations, loopback connections are applied to the multi-bit components from the scan out port to the scan in port of the multi-bit cell or component, therefore, one loopback connection spans multiple sequential cells within the multi-bit cell or component. During certain optimizations, loopback connections are applied to multiple sequential cells that are coupled together but do not necessarily reside in a multi-bit cell or component. By spanning multiple sequential cells, circuit degeneration is reduced thereby providing better circuit optimizations for netlists having scan circuitry.

Electronic design automation system and methods utilizing groups of multiple cells having loop-back connections for modeling port electrical characteristics

A system and method for architecting design for test circuitry (e.g., scan architecting) within an integrated circuit design having subdesigns (e.g., modules). The novel system contains a default operational mode (no user specification) and an operational mode based on user specifications; within either mode, the system recognizes and allows definition of subdesign scan chains which can be linked together alone or with other scan elements to architect complex scan chains (e.g., top level scan chains). The system includes specification, analysis, synthesis and reporting processes which can be used in an IC design having a hierarchical structure including modules. The specification process accesses a design database and a script file and allows a user to define global scan properties (scan style, number of chains, etc.), properties of a particular scan chain (membership, name, etc.), test signals (scan-in, scan-out, scan-enable, etc.), complex elements used as part of a scan chain without requiring scan replacement, wires and latches forming connections between scan elements; this information is associated with the selected design database. Analysis reads the design database and performs architecting of scan chains based on inferred scan elements of the design and defined (e.g. specified) scan elements. During analysis, the logic within the design database is not altered and a script is generated for user modification/verification. Specification and analysis can be executed iteratively until the desired scan structures are planned. Synthesis then implements the desired DFT circuitry by altering the design database based on the scan chains planned by analysis.

Hierarchical scan architecture for design for test applications

A computer implemented process and system for effectively determining a set of sequential cells with a integrated circuit design that can be scan replaced (e.g. for design for test applications) to offer significant testability while still maintaining specified optimization (e.g., area and/or timing) constraints that are applicable to the design. The novel system selects sequential cells for scan replacement that offer best testability contribution while not selecting sequential cells for scan replacement that do not offer much testability contribution and/or are part of most critical paths within the design. The novel system is composed of a subtractive method and an additive method. The subtractive method inputs a fully scan replaced netlist (e.g., the sequential cells are scan replaced) that does not meet determined optimization constraints. The novel subtractive system unscans selected cells until the area and/or timing constraints are met. A flag indicates whether nor not timing is considered. Selection for unscanning is based on a testability cell list (TCL) that ranks cells by their degree of testability contribution; those cells with low degrees of testability are unscanned first. The additive process receives an unscanned netlist (original design) and scan replaces cells, using the TCL ranked list until optimization (e.g., area and/or timing) constraints of the design are violated. A flag indicates whether nor not timing is considered. The additive system iterates through the TCL list with the cells offering the most contribution for testability scan replaced first.

Method and apparatus for performing partial unscan and near full scan

A computer system and computer implemented method for deriving constraints with which to direct automatic integrated circuit layout is disclosed. The present invention is particularly adapted for use in the design of large integrated circuits with complex synchronous timing behavior. Preferably, the invented computer system includes means for storing a netlist data structure within a storage means is provided, the netlist data structure representing a circuit configuration having a plurality of circuit elements and representing static timing information for the circuit configuration; means for selecting specified circuit elements to be used for generating the layout constraints, whereby the specified circuit elements that are selected are fewer than, i.e. represent a proper subset of, the plurality of circuit elements of the circuit configuration; means for identifying a most critical path through each of the specified circuit elements based upon the static timing information, whereby preferably the most critical path is that path having the least slack defined as the difference between a required time at which a signal should reach the specified circuit element and an arrival time at which the signal is expected to reach the specified circuit element; and means for generating layout constraints from the most critical path through each of the specified circuit elements, whereby at least one constraint is generated covering each of the specified circuit elements. Also disclosed is a feature whereby any paths that do no meet specified filter criteria, and paths that are duplicates of others, are discarded, thereby retaining only irredudant critical paths on which to base layout constraints.

Growing community of inventors

Boulder, CO, United States of America

Robert L Walker