JPS6149696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stack formation method used in an information processing device, such as a microcomputer device, to transfer data, for example, to store arguments when branching to a subprogram and a return address to a main program. be.

A conventional example is shown in FIG. A stack pointer 2 is provided in the arithmetic processing unit 1, and a mechanism is formed that allows reading and writing only to the memory in the storage device 3 corresponding to the address indicated by the contents of the stack pointer 2. The stack 4 as a first-in, last-out memory is formed by increasing or decreasing the contents of the stack pointer 2 by, for example, 1 by the address area occupied by one word each time a read or write is performed. Since data can be input and output from the stack 4 without being particularly aware of the memory address in the storage device 3, it is possible to store the return address to the main program at the time of subprogram branching and to store the return address from the subprogram to the main program. It is frequently used for retrieving return addresses, saving and restoring the contents of various registers in the arithmetic processing unit 1, and passing data between programs. In order for the arithmetic processing unit 1 to read and write data to and from the storage device 3 via the bus 5 under the control of the stack pointer 2,
Data delays occur due to the distributed capacity of the bus 5, and data delays occur within the transmission/reception unit and transmission/reception control unit used to connect the processing unit 1 and the bus 5, the storage device 3 and the bus 5, and the transmission/reception control unit. It took a lot of time to convey the message correctly.

The present invention provides a novel method for forming a stack that improves the conventional drawbacks, and includes providing a main (internal) stack within an arithmetic processing unit, thereby achieving the following:
This aims to reduce the frequency of reading and writing to a storage device used as an auxiliary (external) stack via the bus, reduce wasted time in data transfer, and increase speed.

An embodiment of the present invention will be described below based on the drawings. In FIG. 2, an arithmetic processing device 6 includes an external save pointer 7, an internal stack pointer 8, an internal stack 9, and an internal bus 10 that connects these, and a storage device 11 that includes an external save area 12 and a bus 13. are connected via. The external save pointer 7 indicates the empty start position of the external save area 12, and the internal stack pointer 8 indicates the empty start position of the internal stack 9. is written to and read from the internal stack 9 through the internal stack pointer 8, and the internal stack pointer 8 is updated. Furthermore, when the arithmetic processing unit 6 writes to the stack when the internal stack is full, part of the contents of the internal stack 9 is transferred to the external save area 12 based on the values of the internal stack pointer 8 and the external save pointer 7. After, internal stack 9
At the same time, the internal stack pointer 8 and external save pointer 7 are updated. Also, when reading from the stack when the internal stack 9 is empty, a part of the contents of the external save area 12 is transferred to the external save pointer 7,
After transferring to the internal stack 9 based on the value of the internal stack pointer 8, it is read from the internal stack 9, and the internal stack pointer 8 and external save pointer 7 are updated.

Let us now consider the case where the capacity of the internal stack 9 is 2n words and explain in more detail. If a stack usage request occurs during program execution, the internal stack 9
Data is transferred to and from the memory under the control of the internal stack pointer 8. The internal stack 9 is configured to form a register array, and the internal bus 1
Since data is transferred through 0, it can be performed at high speed similar to data transfer between registers within the arithmetic processing unit 6. When a read request occurs when the data stored in the internal stack 9 is 0 words, n words are transferred from the external save area 12 formed in the storage device 11 to the bus bar 13 from the position indicated by the external save pointer 7. The data is stored in the position indicated by the internal stack pointer 8 of the internal stack 9, the position indicated by the external save pointer 7 is subtracted by n, and the position indicated by the internal stack pointer 8 is incremented by n. Thereafter, the internal stack 9 is read. Similarly, when a write request occurs when the data stored in the internal stack 9 is 2n words, n words are written from the internal stack 9 to the external save area 12 via the bus 13 at the position indicated by the external save pointer 7. The position indicated by the external save pointer 7 is incremented by n, and the position indicated by the internal stack pointer 8 is decreased by n. Thereafter, writing is performed to the internal stack 9. In this way, the number of words transferred at one time between the internal stack 9 and the external stack 12 is
By setting it to n instead of 2n, the operation frequency when the number of words stored in the internal stack 9 is 0 or around 2n is reduced, the number of data transfers between the internal stack 9 and the external save area 12 is reduced, and the number of words stored in the internal stack 9 is reduced. Make it easy to exchange data only within the network.

Generally speaking, the internal stack 9 is (i+j+
k) words (where i, k are positive integers, and j is an integer), when writing to the stack when the internal stack 9 is full, one word from the contents of the internal stack 9 is saved to the external save area 12. When reading from the stack when the internal stack 9 is empty, the k word is transferred from the external save area 12 to the internal stack 9.
Transfer to. In the above embodiment, i=k=n, j=0
We have considered the case of , but the combination of values of i, j, and k is not limited to this.

As explained above, in the stack forming method of the present invention, the stack operation is not performed on the storage device, but on the stack register array provided in the arithmetic processing unit as an internal stack. Even when handling a number of words that exceeds the capacity of the internal stack, stack operations are still performed only on the internal stack by temporarily saving information at the bottom of the stack that exceeds the capacity to the external save area. Therefore, high-speed stack operation using the internal stack is always performed regardless of the depth of the stack and the capacity of the internal stack, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional stack forming method, and FIG. 2 is a block diagram showing a stack forming method according to the present invention. 6... Arithmetic processing unit, 7... External save pointer, 8... Internal stack pointer, 9... Internal stack, 10... Internal bus, 11... Storage device,
12... External evacuation area, 13... Bus bar.

Claims (1)

[Claims] 1. Using an information processing device consisting of an arithmetic processing device, a storage device that stores programs to be executed and data handled by the arithmetic processing device, and a bus that connects them,
When forming a first-in, last-out stack for data exchange within a program, an external save area is provided in the storage device, an internal stack is provided in the arithmetic processing unit, and an internal stack pointer indicates the empty head position of the internal stack. , has an external save pointer indicating the empty head position of the external save area, and when the arithmetic processing unit performs a write/read operation to/from the stack, it writes/reads data to/from the internal stack and also points to the internal stack pointer. When writing to the stack when the internal stack is full, the contents of the internal stack are transferred to the external save area, and after the full state is cleared, the contents are written to the internal stack, and the internal stack pointer and the external save area are updated. When updating the pointer and reading from the stack when the internal stack is empty, the contents of the external save area are transferred to the internal stack, and after the empty status is resolved, reading from the internal stack is performed, and the internal stack pointer and the A stack forming method characterized by having a function of updating an external save pointer. 2 When the internal stack is composed of (i+j+k) words (where i, k are positive integers, and j is an integer), and the internal stack is full, the lower (oldest) i of the contents of the internal stack is written.
This function transfers the word to the top (top) of the external save area, and when reading from the stack when the internal stack is empty, transfers the top (newest) k words from the external save area to the top (top) of the internal stack. A method of forming a stack according to claim 1.