JP2576360B2 - Timing-aware placement equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a layout design, and more particularly to a timing-aware arrangement.

[0002]

2. Description of the Related Art When an area, a block belonging to a certain area, a connection relation between the blocks, and a net circuit operation speed limit indicating a connection relation between a block belonging to other than the area and a block belonging to the area are given, A problem arises in that a cut line that divides the region into two is created, and the position of a block that shortens the critical path length is determined so that the number of nets crossing the cut line is minimized.

FIG. 2 shows a conventional arrangement of this type. This arrangement device includes a cut line creating device 202 for creating a cut line, a merge partner selecting device for determining a merging partner of each block from each block coupling degree, and a merging unit 201 for performing a merging process of blocks obtained by the merging partner selecting device 201. Pairwise device 204 for performing pair exchange so as to minimize the number of devices 203 and the number of nets crossing the cut line
Was composed of (Masato Edahiro
and Takeshi Yoshimura, "N
ew Placemmet and Global R
outAlgorithms for Stan
dard Cell Layouts ", Proc. 2
7th DA Conf pp. 642-645, (1
990)).

[0004]

To solve the above problem, conventionally, a merging partner is selected only based on the degree of connection of each block, a merging process is performed, and then the number of nets crossing the cut line is minimized. In this manner, the pair exchange is performed as described above, and a result satisfying the critical path cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a timing-aware placement apparatus which shortens a critical path and minimizes the number of nets crossing a cut line.

[0006]

According to a first aspect of the present invention, there is provided a timing-considering arrangement apparatus comprising: a set of blocks belonging to a certain area of a circuit; and a netlist representing a connection relationship between the blocks.
Input the operation speed limit of the circuit and the internal delay value of the circuit, perform timing analysis, find the required time and arrival time of each net, find the margin of each net, and extract the critical path from the margin Critical path extraction device, and input the placement area of the netlist and the circuit,
A cut line generation device that generates a cut line in the placement area and determines a block position of the block; and inputs the block position, the net list, the margin, and the area limit of the merged block, and Calculating a merging cost between blocks satisfying the area limitation of the block based on the merging degree and the margin, inputting the netlist and a delay-considering merging partner selecting device for determining a block to be merged; The merge device that merges the blocks determined by the delay-considering merge partner selection device and updates the netlist, the netlist updated by the merge device, the cut line, and the block position are input, and Pairwise equipment that performs block exchange processing so that the number of nets crossing the cut line is minimized To characterized in that it is composed of a. According to a second aspect of the present invention, there is provided a timing-considering arrangement apparatus which inputs a set of blocks belonging to a certain area of a circuit, a netlist indicating a connection relationship between the blocks, an operation speed limit of the circuit, and an internal delay value of the circuit. , Perform timing analysis,
The required time and arrival time of each net are determined, the margin of the net is determined, and the critical path is extracted based on the margin, and the number of paths passing through each net with the net list as input (path passing) A pass-through density extracting device for calculating the density, a cut line generating device for inputting the netlist and the arrangement area of the circuit, generating a cut line in the arrangement area, and determining a block position of the block; a list, and the cut line, the type of the block position, the fewer nets crossing a cut line, and the critical path number is small across the cut line, and less high net of paths passing density across the cut line And a pair-wise device for performing pair exchange.

[0007]

FIG. 1 shows an embodiment of the timing-considering arrangement apparatus according to the first invention. FIG. 12 shows the overall flow of the present invention.
Shown in

As inputs, a net list (a set of blocks and a connection between blocks (net)), an operation speed limit of the circuit (the operation must be performed in a few ns),
When the internal delay value of the circuit is given, the critical path extraction device 101 performs a timing analysis to obtain a required time and an arrival time of each net. Timing analysis is the time of arrival at each net from the input to the output at the latest, i.e., the arrival time, and from the output to the input, how long it must arrive at the net from the input to meet the delay. The required time, that is, the required time is obtained. The arrival time (request time) is the internal delay (and wiring delay) of the block on the path from the input (output) to the net
Can be obtained by adding (subtracting) FIG.
(A) shows the result of delay analysis when the operation speed limit of the circuit is 22. (Request time and arrival time are Robert
B. Hitchcock, Gordon L. Smit
h, David D.H. Cheng, "Timing A
analysis of Computer Hardw
are ", IBM J. Res. Develop. vo
11 January 1982, pp. 139-143. 100-10
5, (1982). Can be obtained by Then, slack (request time-arrival time) of each net is obtained, and slack distribution processing is performed to obtain a margin of each net (12-1). What is slack distribution?
Take a net whose slack is not 0, divide the slack value into nets on the path passing through the net,
This is a process of allocating as a margin. When the margin is allocated, the margin is added to the wiring delay, and the delay analysis is performed again. Thereafter, a slack distribution process is performed. This process is repeated until the slack values of all nets become almost zero. (The margin is, for example, Peter S. Hauge,
Ravi Nair, Ellen J, Yoffa,
“Circuit Placement for Pr
editable Performance ", Pr
oc. ICCAD-87. Pp. 88-91, (19
87). Can be obtained by FIG. 7B shows the result of the distribution of the margin. A net with a negative margin is a net on the critical path. The smaller the margin, the tighter the limit. Here, the critical path is a path (a series of nets) in which the required time minus the arrival time is negative.

Next, the cutline creating apparatus 103 receives the netlist and the arrangement area as input, creates a cutline in the arrangement area, and determines whether each block belongs to the right or left of the cutline. (12-2).

Next, in the delay consideration merging partner selection device 102, the block position (whether the block belongs to the right or left of the cut line) and the net list (updated by the merge process, determined by the cut line creation device 103). And a critical path extraction device 10
The margin of each net obtained in step 1 and the area limit of the merged block are input, and first, the degree of connection between blocks (how many nets exist between block i and block j) is obtained. In the example of FIG. 8, the coupling degree between block A and block B is 1, and the coupling degree between block B and block C is 2. Next, a merging cost is calculated for blocks satisfying the block area limit based on the coupling degree and the margin, and a block to be merged is determined. (FIGS. 11 and 12-3).

Hereinafter, a method for obtaining a merge cost cost (i, j) when merging blocks i and j will be described. Let the degree of connection of the net between the block i and the block j be nonect (i, j). A set of nets connecting block i and block j

[0012]

(Equation 1)

It is assumed that: Aford the margin of net i
(I). In the delay consideration merging partner selection device, a set of all blocks belonging to the same area (block i, j)
On the other hand, if the sum of the areas of the blocks i and j is equal to or less than the limit value, the merge cost:

[0014]

(Equation 2)

The merge cost between blocks is obtained by calculating Here, α and β are arbitrary variables.

The blocks to be merged are sorted in ascending order of merge cost, and have the largest value.

The merging device 104 inputs the netlist and the target block and the number of target blocks obtained by the delay consideration merging partner selection device 102 and performs a merging process (12-4). The merge process is a process of updating two net blocks into one block by using two input blocks. FIG. 9 shows a case where blocks a and b are merged into block c. If the number of blocks has reached the target number of blocks, or the block to be merged determined by the delay-considering merge partner selection device is empty, control is passed to the pair-wise device 105; Moving.

The pairwise device 105 receives the net list updated by the merge device, the cut line and the block position obtained by the cut line creating device as inputs, takes out blocks one by one from both sides of the cut line, and outputs the nets crossing the cut line. (Pairwise) (FIG. 10, 12-6) so that the number of blocks becomes minimum (so that the number of nets crossing the cut line is minimum and the number of critical paths crossing the cut line is minimum). ).
Pairwise includes (Masato Edahiro a
nd takeshi Yoshimura, “New
Placemet and Global Rou
ting Algorithms for Stand
ard cell Layouts ". Proc. 27
th DA Conf pp. 642-645, (19
90)) can be used.

FIG. 14 shows the pass passage density. In this example, a path passing through nets 1, 3, 5 and nets 2, 4,
5 is present. Block 1 and Block 5
Is severe, the two paths can be shortened by shortening the net 5, but if the net 1 is shortened, only one path can be shortened. By shortening the net in this way, a net that can shorten many paths, that is, by shortening a net through which many paths pass, a plurality of critical paths remain without satisfying the delay due to a certain net. Can be prevented.

In the example of FIG. 3, the number of paths passing through the net 1 is one, the number of paths passing through the net 2 is one, and the number of paths passing through the net 3 is one. , Net 4
Is one, and the number of paths passing through the net 5 is two. Therefore, the net 5 may be shortened.

FIG. 13 shows an embodiment of the timing-considering arrangement apparatus according to the second invention.

FIG. 18 shows the overall flow.

The path passing density extracting apparatus receives a net list (a set of blocks and a (net) representing a connection between blocks) as an input and obtains the number of paths passing through each net. First, the number of paths from the starting point to each net is determined. (Level each net according to the number of nets from the starting point (Fig. 15). Next, add the number of paths from the starting point of the net entering the block from which the net comes out in descending order of level, The number of paths from the start point of the net is the number of paths.
Is the number of passes from the starting point. If the block on which the net appears is the start block, the number of paths from the start point of the net is set to one. Next, count the number of passes from the end point to each block. (From the end point side, the same processing as the start point side is performed. (FIG. 16)) Next, each block is multiplied by the number of paths from the start point to each block and the number of paths from the end point to each block. The number of paths passing through the block is obtained (FIG. 17).

In the critical path extraction device, when a netlist, an operation speed limit of a circuit (the operation must be performed at a certain ns), and an internal delay value of a circuit to which an internal delay value of the circuit is given, a timing is determined. Analysis is performed to determine the required time and arrival time of each net. Timing analysis is the time of arrival at each net from the input to the output at the latest, i.e., the arrival time, and from the output to the input, how long it must arrive from the input to the net to satisfy the delay. The required time, that is, the required time is obtained. The arrival time (request time) can be obtained by adding (subtracting) the internal delay (and the placement delay) of the block on the path from the input (output) to the net. FIG. 7A shows the result of the delay analysis when the operation speed limit of the circuit is 22. (Request time and arrival time are Robert
B. Hitchcock, Gordon L. Smit
h, David D.H. Cheng, "Timing A
analysis of Computer Hard-
ware ", IBM J, Res. Develop.v
ol1 January 1982, pp. 100-1
05, (1982). Can be obtained by Thereafter, slack (request time-arrival time) of each net is obtained, and slack distribution processing is performed to obtain a margin of each net. Slack distribution processing means that slack is 0
This is a process of taking out a net that is not and dividing the slack value into nets on a path passing through the net and assigning the result as a margin. When the margin is allocated, the margin is added to the wiring delay, and the delay analysis is performed again. Thereafter, a slack distribution process is performed. This process is repeated until the slack values of all nets become almost zero. (The margin is, for example, Peter S. Hauge, RaviN
air, Ellen J, Yoffa, "Circui
t Placement for Predictab
le Performance ", Proc. ICCA
D-87. Pp. 88-91, (1987). Can be obtained by FIG. 7B shows the result of the distribution of the margin. A net with a negative margin is a net on the critical path. The smaller the margin, the tighter the limit. Here, the critical path is the required time-
A path with a negative arrival time (a series of nets).

Next, the cut line creating apparatus inputs a net list and an arrangement area, creates a cut line in the arrangement area, and determines whether each block belongs to the right or left of the cut line.

In the pairwise apparatus, the number of paths passing through each net obtained by the path passing density extraction apparatus, the margin of each net obtained by the critical path extraction apparatus, the net list, and the cut line obtained by the cut line creation apparatus. And block position as inputs, take out blocks one by one from the cut line area, and minimize the number of nets crossing the cut line (the minimum number of nets crossing the cut line and the critical path crossing the cut line) Block exchange processing (pairwise) is performed so that the number is the smallest and the number of nets having a high path passing density across the cut line is the smallest. Pairwise, (Masato E
dahiro and takeshiYoshimu
ra, “New Placement and Glo
balRouting Algorithms for
Standard cell Layouts ".P
rc. 27th DA Conf pp. 642-6
45, (1990)). That is, the cost exch when exchanging the block i and the block j
The angle (i, j) is defined as follows, assuming that a set of nets connected to the blocks i and j is E2.

[0027]

Here, aford (l) represents the margin of the net, and form (l, a ) is the pin of the net l.
a represents the number of nets that traverse a cut line that changes by moving a to the opposite region, and path (l) is
This represents the passing density of the net l. P (l) is a pin connected to the net l and represents a set of pins of blocks i and j . α is an arbitrary constant.

Exchange (i, j) is calculated for all sets of blocks, and the one with the highest cost is to be exchanged, and exchange is performed. This exchange processing is performed until the number of nets crossing the cut line, the number of critical paths crossing the cut line, and the number of nets having a high path passage density crossing the cut line do not decrease.

[0030]

FIG. 3 shows the result of creating a cut line and extracting a critical path for one input example for the embodiment of FIG. In FIG. 3, circles numbered 1, 2,... Represent blocks (3-1). The line connecting each block represents a net (3-2). The bold line indicates the critical path (3-
3). 3-4 represents a cut line.

In the conventional method, when the merging partner is selected, it is determined only by the degree of coupling, so that block 1 and block 2 are coupled, block 3 and block 4 are coupled,
Block 5 and block 6 are combined, and block 7 and block 8 are combined (FIG. 4). If pairwise is performed in this state, the number of nets crossing the cut line cannot be reduced any more. At this time, the critical path crosses the cut line three times and is long.

However, according to the present invention, when a merge partner is selected, the delay-considering merge partner is selected by the selecting device using not only the degree of coupling but also the critical path information extracted by the critical path extracting device. Block 1 and block 4 are combined, block 2 and block 3 are combined, block 6 and block 7 are combined, and block 5 and block 8 are combined (FIG. 5). On the other hand, when the pair exchange is performed, the result of FIG. 6 is obtained. In this case, the critical path crosses the cut line only once, and a short critical path is obtained.

As described above, in the present invention, the number of nets crossing the cut line can be minimized, and the critical path can be shortened. Also,
In the second invention, since the exchange processing is performed with priority given to the net having the higher density, it is possible to prevent a plurality of critical paths from remaining due to a certain net without satisfying the delay. In addition, block concentration is prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional arrangement device.

FIG. 3 is a diagram showing a result of extracting a critical path.

FIG. 4 is a diagram showing a state of connection of blocks according to a conventional technique.

FIG. 5 is a diagram showing a state of connection of blocks according to the present invention.

FIG. 6 is a diagram showing a result of performing pair exchange on the block of FIG. 5;

7A is a diagram showing a result of delay analysis in a case where the operation speed of the circuit is limited to 22. FIG. 7B is a diagram showing a result of distributing a margin.

FIG. 8 is a diagram showing an example of combining blocks;

FIG. 9 is a diagram showing a merge result;

FIG. 10 is a diagram showing a block exchange process.

FIG. 11 is a diagram showing a flow of determining a block to be merged;

FIG. 12 is a diagram showing an overall flow of a timing-considered arrangement according to the present invention;

FIG. 13 is a diagram showing a second embodiment of the present invention.

FIG. 14 is a diagram showing a pass passage density;

FIG. 15 is a diagram showing the number of paths from a start point to each net.

FIG. 16 is a diagram showing the number of paths from an end point to each net.

FIG. 17 is a diagram showing the number of paths passing through each net.

FIG. 18 is a diagram showing the flow of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Critical path extraction device 102 Delay consideration merge partner selection device 103 Cut line creation device 104 Merge device 105 Pairwise device 201 Merge partner selection device 202 Cut line creation device 203 Merge device 204 Pairwise device

Claims (2)

(57) [Claims] A timing analysis is performed by inputting a set of blocks belonging to a certain region of a circuit and a netlist representing a connection relationship between the blocks, an operation speed limit of the circuit, and an internal delay value of the circuit. Calculating a required time and an arrival time of each net; obtaining a margin of each net; extracting a critical path based on the margin; and inputting the netlist and the arrangement area of the circuit; A cut line generating apparatus that generates a cut line and determines a block position of the block; and inputs the block position, the net list, the margin, and the area limit of the merged block, and connects the blocks. The merge cost between blocks satisfying the area limit of the block based on the coupling degree and the margin, and the block to be merged is calculated. A delay-considering merge partner selection device that determines the net list, a merge device that takes the netlist as an input, merges the blocks determined by the delay-consideration merge partner selection device, and updates the netlist; and a net updated by the merge device. A timing-aware placement device, comprising: a list, the cut line, and a pair-wise device for inputting the block position and exchanging blocks so as to minimize the number of nets crossing the cut line. . 2. A timing analysis is performed by inputting a set of blocks belonging to a certain area of a circuit and a netlist representing a connection relationship between the blocks, an operation speed limit of the circuit, and an internal delay value of the circuit. A critical path extraction device for obtaining a required time and an arrival time of each net, obtaining a margin of the net, and extracting a critical path based on the margin; and a number of paths (path passing) Density extraction device for determining the density
A cut line generating apparatus for inputting the net list and the arrangement area of the circuit, generating a cut line in the arrangement area, and determining a block position of the block; the net list, the cut line, and the block position Enter the number of nets crossing the cut line
Less, and the critical path number is small, and timing consideration device comprising a pair-wise device for performing paired exchange as net high-pass passage density across the cut line is reduced across the cut line.