JPS59211152A - Branch source storage method for digital computers - Google Patents

Abstract

PURPOSE:To facilitate an analysis of fault and a program test by storing an address where a branch instruction exists to a branching origin storing memory set immediately before an instruction serving as the branching destination an unconditional or conditional branch instruction within a program storing memory area. CONSTITUTION:When a program of a program storing memory 3 and a branch instruction 4 are executed, the branching origin address is stored in a branching storing origin memory 5 of the memory 3. If a problem such as a program fault, etc. occurs after execution of the program, the memory is traced reversely. Thus it is immediately understood which part the program is executing to reach the relevant faulty area.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a branch source storage system for branch instructions in a digital computer.

FIG. 1 is a diagram showing the structure of a memory 1 dedicated to storing branch destination addresses, for explaining a conventional branch source storage method of a digital computer. In the figure, 2 is a storage unit of the memory 1 dedicated to storing branch destination addresses.

Next, the operation of the branch destination storage method of the digital computer configured as described above will be explained.

First, in the process of executing a program, when a branch instruction is executed, the branch destination address of the branch instruction is stored in the storage unit 2 that stores the oldest branch destination address of the memory 1 dedicated to storing branch destination addresses. As a result, the memory 1 dedicated to storing branch destination addresses always stores the address of the branch instruction executed most recently. Therefore, when a failure occurs, by referring to the contents of the branch destination address storage memory 1, the execution state of the branch instruction immediately before the failure occurs can be determined.

However, in the conventional branch destination storage method of a digital computer, the number of branch destination addresses that can be saved is limited by the number of storage units of the memory 1 dedicated to storing branch destination addresses. Particularly when a program goes out of control immediately before a fault is detected, there is a drawback that analysis cannot be performed using only the branch destination address stored in the branch optical address storage memory 1.

Therefore, an object of the present invention is to memorize the branch sources of all branch instructions for a running program when a fault occurs, and to use a digital system that can effectively analyze even if the program goes out of control immediately before the fault is detected. This provides a branch source storage method for computers.

In order to achieve such an object, the present invention stores a branch source address in a program storage memory area in pairs with an unconditional or conditional branch instruction. will be explained in detail.

FIG. 2 is a diagram showing the configuration of a program storage memory showing a branch source storage method of a digital computer according to an embodiment of the present invention. In the figure, 3 is a program storage memory, 4 is an unconditional or conditional branch instruction, and 5 is a branch source storage memory that stores the branch source address of the branch instruction. Note that this branch source storage memory 5 is arranged so as to be located immediately before the instruction to which the branch instruction branches.

Next, the operation of the branch source storage method of the digital computer according to the above configuration will be explained.

First, when the program in the program storage memory 3 is executed and the branch instruction 4 is executed, the branch source address is stored in the branch source storage memory 5 of the program storage memory 3. Therefore, if a problem such as a program failure occurs after program execution, by tracing back this branch source storage memory 5, it can be immediately determined which part the program was executing when reaching the problematic part.

As described above, according to the branch source storage method of the digital computer of the present invention, when a fault occurs, the operation of the program leading up to the fault can be traced (in the reverse direction) regardless of the number of branch instructions. It also has the effect of being able to be effectively used for program testing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a memory dedicated to storing branch destination addresses for explaining a conventional branch destination storage system in a digital computer, and FIG. 2 shows a branch source storage system in a digital computer according to an embodiment of the present invention. FIG. 3 is a diagram showing the configuration of a program storage memory. (3) 1...Memory dedicated to storing branch destination address, 2...Storage unit, 3...Program storage memory, 4...Branch instruction, 5...Branch source memory Codes indicate the same or equivalent parts. Agent Masuo Oiwa (4) 1st Cause Figure 2

Claims (1)

[Claims] In a branch source storage system of a digital computer that allows fault analysis or program testing up to the occurrence of a fault in a running program when a fault occurs, branching of an unconditional or conditional branch instruction is performed within a predetermined area of the program storage memory. A branch source storage method for a digital computer, characterized in that an address where the branch instruction exists is stored in a branch source storage memory immediately before a previous instruction.