Exception handling method and apparatus for use in program code conversion

#The present invention relates in general to the field of program code conversion for computer systems and in particular, but not exclusively, to the field of emulation using dynamic binary translation.

#A program for a computer takes several different forms. Typically a program is written first in a high-level language readily understood by a human programmer. The program is compiled from the high-level language into a low-level language more appropriate for control of a computer's processor and related components. However, in order for the processor to function, the program code must be provided in a machine-readable form that directs primitive operations of the processor such as loading, shifting, adding and storing operations. To run faster, some processors use an expanded set of instructions each of which represent a sequence of primitive instructions. This is known as a complicated instruction set computer (CISC). However, program code written (or compiled) specifically for a first processor with a particular instruction set in most cases cannot run on any other type of processor because of differences between the instruction set for each type of processor.

#An emulator allows program code written for a processor of a first type (a “subject” processor) to be run on a processor of a second type (a “target” or “host” processor). One form of this emulation process is known as binary translation because executable binary code appropriate to the subject processor is translated into executable binary code appropriate to the target processor.

#For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

#FIG. 1 shows a typical prior art configuration for a subject processor;

#FIG. 2 shows a typical emulator using binary translation;

#Referring to FIG. 1 a typical prior art arrangement is shown illustrating the configuration of a subject machine wherein subject code 10 is executed directly on a subject processor 11. Suitably the subject code is executable binary code. However, the subject code may be represented in any suitable language with intermediate layers (compilers, etc.) between the subject code 10 and the subject processor 11 as will be familiar to the skilled person.

#Referring now to FIG. 2, a typical prior art configuration is shown to illustrate the use of a binary translation type emulator 20 as an intermediate layer enabling the subject code 10 to be executed by a target processor 31. The preferred embodiment of the present invention is particularly intended for use with an emulator 20 which performs dynamic binary translation of the subject code 10 into target code 30 executable on the target processor 31.

#Referring now to FIG. 3 the emulator 20 of the preferred embodiment is illustrated in more detail and comprises a front end 21, a core 22 and a back end 23.