摘要:
A fast technique for circuit optimization in a physical synthesis flow iteratively repeats slew-driven (timerless) buffering and repowering with a changing slew target. Buffers are added as necessary with each iteration to bring the nets in line with the new slew target, but any nets having positive slack from the previous iteration are skipped, and that slack information is cached for future timing analysis. Buffer insertion is iteratively repeated with incrementally decreasing slew until a minimum slew is reached, or when none of the nets have negative slack. Iteratively repeating the timerless buffering and repowering while gradually decreasing the slew constraint in this manner results in a design structure which retains high quality of results with significantly smaller area and wire length, and with only a small computational overhead.
摘要:
The present disclosure is directed to a method for determining a plurality of buffer insertion locations in a net for an integrated circuit design. The method may comprise calculating a plurality of resistive-capacitive (RC) influences in parallel, each RC influence corresponding to one of a plurality of buffering options available for a first sub-tree for the addition of a wire segment to the first sub-tree; updating the plurality of RC influences for the addition of a buffer for the first sub-tree, the buffer comprising one of a plurality of buffer types; and merging the first sub-tree with a second sub-tree in parallel by grouping the plurality of buffering options available for the first sub-tree and a plurality of buffering options available for the second sub-tree into a plurality of merging groups, and merging at least two groups of the plurality of merging groups in parallel.
摘要:
The present disclosure is directed to a method for determining a plurality of buffer insertion locations in a net for an integrated circuit design. The method may comprise calculating a plurality of resistive-capacitive (RC) influences in parallel, each RC influence corresponding to one of a plurality of buffering options available for a first sub-tree for the addition of a wire segment to the first sub-tree; updating the plurality of RC influences for the addition of a buffer for the first sub-tree, the buffer comprising one of a plurality of buffer types; and merging the first sub-tree with a second sub-tree in parallel by grouping the plurality of buffering options available for the first sub-tree and a plurality of buffering options available for the second sub-tree into a plurality of merging groups, and merging at least two groups of the plurality of merging groups in parallel.
摘要:
A physical synthesis tool for dock optimization with local clock buffer control optimization is provided. The physical synthesis flow consists of delaying the exposure of clock routes until after the clock optimization placement stage. The physical synthesis tool clones first local clock buffers. Then, the physical synthesis tool runs timing analysis on the whole design to compute the impact of this necessarily disruptive step. After cloning local clock buffers, the physical synthesis tool adds an extra optimization step to target the control signals that drive the local clock buffers. This optimization step may includes latch cloning, timing-driven placement, buffer insertion, and repowering. The flow alleviates high-fanout nets and produces significantly better timing going into clock optimization placement. After placement, the physical synthesis tool fixes latches and local clock buffers in place, inserts clock routes, and repowers local clock buffers.
摘要:
Global routing congestion in an integrated circuit design is characterized by computing global edge congestions and constructing a histogram of averages of the global edge congestions for varying percentages of worst edge congestion, e.g., 0.5%, 1%, 2%, 5%, 10% and 20%. Horizontal and vertical global edges are handled separately. Global edges near blockages can be skipped to avoid false congestion hotspots. The histogram of the current global routing can be compared to a histogram for a previous global routing to select a best routing solution. The histograms can also be used in conjunction with congestion-driven physical synthesis tools.
摘要:
The input slew at a selected gate of an integrated circuit design is computed by assigning a default slew rate to the output gate of a previous logic stage which is greater than a median slew rate for the design. This default slew rate is propagated through the logic stage to generate an input slew rate at the selected gate. The default slew rate corresponds to a predetermined percentile applied to a limited sample of preliminary slew rates for randomly selected gates in the design. The default slew rate is adjusted as a function of known characteristics of the wirelength from the output gate to a first gate in the second logic stage. The delay of the selected gate is calculated based on the input slew rate. The input slew rate can be stored during one optimization iteration and used as a default slew rate during a later optimization iteration.
摘要:
A timing-driven cloning method iteratively partitions sinks of the net into different sets of clusters and for each set computes a figure of merit for a cloned gate location which optimizes timing based on linear delay, that is, a delay proportional to the distance between the cloned gate location and the sinks. The set having the highest figure of merit is selected as the best solution. The original gate may also be moved to a timing-optimized location. The sinks are advantageously partitioned using boundaries of Voronoi polygons defined by a diamond region surrounding the original gate, or vice versa. The figure of merit may be for example worst slack, a sum of slacks at the sinks in the second cluster, or a linear combination of worst slack and sum of the slacks.
摘要:
A method, data processing system and computer program product for optimizing the placement of logic gates of a subcircuit in a physical synthesis flow. A Rip Up and Move Boxes with Linear Evaluation (RUMBLE) utility identifies movable gate(s) for timing-driven optimization. The RUMBLE utility isolates an original subcircuit corresponding to the movable gate(s) and builds an unbuffered model of the original subcircuit. Notably, a new optimized placement of the movable gate is yielded to optimize the timing (i.e., maximize the minimum slack) of the original subcircuit, while accounting for future interconnect optimizations. The new subcircuit containing the new optimized gate placement and interconnect optimization is evaluated as to whether a timing degradation exists in the new subcircuit. If a timing degradation exists in the new subcircuit, the RUMBLE utility can restore an original subcircuit and a timing state associated with the original subcircuit.
摘要:
A physical synthesis tool for dock optimization with local clock buffer control optimization is provided. The physical synthesis flow consists of delaying the exposure of clock routes until after the clock optimization placement stage. The physical synthesis tool clones first local clock buffers. Then, the physical synthesis tool runs timing analysis on the whole design to compute the impact of this necessarily disruptive step. After cloning local clock buffers, the physical synthesis tool adds an extra optimization step to target the control signals that drive the local clock buffers. This optimization step may includes latch cloning, timing-driven placement, buffer insertion, and repowering. The flow alleviates high-fanout nets and produces significantly better timing going into clock optimization placement. After placement, the physical synthesis tool fixes latches and local clock buffers in place, inserts clock routes, and repowers local clock buffers.
摘要:
A method, data processing system and computer program product for optimizing the placement of logic gates of a subcircuit in a physical synthesis flow. A Pyramids utility identifies and selects movable gate(s) for timing-driven optimization. A delay pyramid and a required arrival time (RAT) surface are generated for each net in the selected subcircuit. A slack pyramid for each net is generated from the difference between the RAT surface and delay pyramid of each net. The slack pyramids are grown and tested using test points to generate a worst-case slack region based on a plurality of slack pyramids in the selected subcircuit. The worst-case slack region is mapped on a placement region and a set of coordinates representing the optimal locations of the movable element(s) in the placement region are determined and outputted.