JPS61276029A - Stack control method - Google Patents

Abstract

PURPOSE:To eliminate the initialization of a variable area and to execute stack control at a high speed by modifying and outputting the value of the value stack by the value of index stack to show whether the variable area designated by the value of the value stack is valid or invalid. CONSTITUTION:When the value of the variable area written in a value stack 10 is read, the pointer to designate the variable area is set to a stack pointer 12. Thus, the value of the variable area, for example, the data of 32 bits are outputted from the stack 18, and the value (the value to show the validity/ invalidity of the value of the variable area) of one bit is outputted from a valid stack 18. From the stack 18, one bit data are supplied to a multiplexer 14 and the selecting control is executed. Thus, when one bit data show the validity, the value from the stack 10 is outputted to an output signal line 16, and when the data show the invalidity, the value of the variable area determined beforehand from a constant generating circuit 15 is outputted onto the signal line 16 as an initial value. In such as way, the necessity to execute the clear initialization of the value stack is eliminated.

Description

[Detailed Description of the Invention] [Summary] The value of the value stack is modified and outputted by the value of the index stack indicating the validity or invalidity of the variable area specified by the value of the value stack, thereby converting the value of the stack variable area into a value. It is now possible to output without initializing the stack. Thereby, it is possible to speed up the stack control processing.

[Industrial application field]

The present invention relates to a stack control method, and more particularly to a stack control method that eliminates the need to initialize variable areas provided on the stack.

High-level language programs used in computers, etc., such as LI
In PS and PROLOG, variable values used in the program are secured in a variable area on a stack in the memory space of a computer, etc., and held there. , the variable area is used while being repeatedly allocated, and its initial value must be a desired value, so the high-speed processing tends to be lost. This is contrary to the desire to run programs at high speed, and there is a need for technical means that can solve this inconvenience.

[Conventional technology]

Conventionally, when allocating a variable area on a stack, the initial value of the variable area is undefined, so it is necessary to initialize it. This is because the nature of the stack is that it is repeatedly rewritten and referenced.

[Problem that the invention seeks to solve]

Explicit initialization is indispensable for allocating variable areas as described above, but this process takes time.
Programs cannot be processed at high speed, hindering improvements in system performance.

The present invention was created in view of the above-mentioned problems, and an object of the present invention is to provide a stack control method that can speed up stack control processing by eliminating the need to initialize the stack variable area.

[Means for solving problems]

FIG. 1 shows a block diagram of the principle of the present invention.

In this figure, ■ is a value stack provided in a system such as a computer that requires assignment and reference of variable values by allocating a variable area on the stack, and this is a value stack that stores the values of the variable area. 2 is an index stack that indicates whether the variable area specified by the value of value stack 1 is valid or not.

3 is a modification means for modifying the value of value stack 1 by the contents of index stack 2;

[Effect]

When a stack address is specified, the value of the variable area is output from the value stack l, and a variable area valid/invalid signal is generated from the index stack 2. When a valid signal is generated from the index stack 2, the value from the value stack l is output from the modification means 3 as a value in the variable area, but when an invalid signal is generated, the modified value is output. It is output from the modification means 3 as the initial value of the variable area.

Therefore, there is no need to explicitly initialize value stack 1.

〔Example〕

FIG. 2 shows an embodiment of the invention.

In this figure, numeral 10 is a value stack provided in a system such as a computer that allocates a variable area on a stack and uses the variable area for program processing, and stores the values of the variable area. The value to be stored is sent via the input signal line 11 and stored in the storage area of the value stack 10 pointed to by the pointer set in the stack pointer 12, and
from which it is read out via line 13 to multiplexer 1.
4. The output of a constant generation circuit 15 is connected to the multiplexer 14, and a selection signal for selecting one of these two inputs and outputting it on an output signal line 16 is supplied from a line 17.

Line 17 is valid stack (index stack) 1
It is connected to the output of 8.

The valid stack 18 stores bits indicating validity/invalidity (“1”/“O”) corresponding to each value stored in the value stack 10. The focus storage means is “1”
” and “0”, a multiplexer 21 and a reset circuit 22.

The stack control mode under the above configuration will be explained below.

When setting the value of a variable area in the value stack 10, the value, for example, 32 bits, is sent to the value stack 10 via the input signal line 11, and the storage area in which the value is stored in the value stack 10 is specified. Pointer is stack pointer 1
2 to the access unit 10A of the value stack 10, and the value of the variable area is stored in the storage area indicated by the pointer t. At the same time, the pointer of the hester pointer 12 of the valid stack 18 is sent, and the constant "1" from the supply means 19 is selected by the multiplexer 21 and written into the storage area specified by the pointer. This makes the value in the variable area valid. Conversely, when indicating invalidity of the value in the variable area, the constant "O" from the supply means 20 is selected by the multiplexer 21 and written. Selection control of multiplexer 21 is performed by reset circuit 22.

When reading the value of the variable area written to the value stack 10 as described above, a pointer designating the storage area to be read is set in the stack pointer 12. As a result, the value of the variable area, for example, 32-bit data, is output from the value stack 10, and the valid stack 18 outputs 1-bit data (a value indicating validity/invalidity of the value of the variable area).

One bit data from this valid stack 18 is provided to multiplexer 14 to effect its selection control. As a result, when the 1-bit data indicates validity, the value from the value stack 10 is output onto the output signal line 16, and when it indicates invalidity, the value from the predetermined variable range from the constant generation circuit 15 is output. The value is outputted onto the output signal line 16 as an initial value.

Thus, there is no need for explicit initialization of the value stack.

The role of the content of the output signal line 18 from the value stack 10 and the constant generation circuit 15 to the output signal line 16 is not only to control the selection described above, but also to provide a valid initial value to the value stack IO. The modification system may be configured to output the initial value on the line 16 when the initial value is no longer available.

[Effects of the Invention] As explained above, according to the present invention, there is no need to explicitly initialize the value stack, so variable areas can be allocated at high speed, which is useful for improving system performance.

[Brief explanation of drawings]

Figure 1 is a block diagram of the principle of the present invention. FIG. 2 is a diagram showing an embodiment of the present invention. In Figure 1 1 is a value stack, 2 is the index stack, 3 is a modification means. Haraori block diagram of the present invention Figure 1

Claims (1)

[Claims] In a system that allocates a variable area on a stack and uses that variable area for program processing, is the value stack (1) that stores the value of the variable area and the variable area specified by the value of the variable area valid? Allocating a variable area without initializing the value stack by providing an index stack (2) that indicates whether or not to use the index stack, and a modification means (3) that modifies the value stored in the value stack by the value of the index stack. A stack control method characterized by being able to perform the following.