Data processing: software development – installation – and managem – Software program development tool – Translation of code
Reexamination Certificate
1999-01-12
2001-08-28
Chaki, Kakali (Department: 2762)
Data processing: software development, installation, and managem
Software program development tool
Translation of code
C717S152000, C717S152000, C710S262000, C710S263000, C710S264000
Reexamination Certificate
active
06282705
ABSTRACT:
BACKGROUNDS OF THE INVENTION
1. Field of the Invention
The present invention relates to a compiler that translates a source program into an object program and an optimization method by the compiler, and more particularly, to a compiler capable of reducing interrupt handling and its optimization method.
2. Description of the Related Art
It is necessary for a compiler which is intended for a device having an interrupt handling function in its architecture to deal with the above interrupt handling function at the compile time. Generally, a routine branching at the occurrence of interruption in a device, that is, an interruption function is designed to be described in a source program, thereby making it possible to deal with the above interrupt handling function.
The interruption function branches irregularly during the execution of a source program. In order to protect the content of a register which has been used before branching, all the contents of the registers that may be used must be saved at the start of the interruption function, and the contents of the saved registers must be returned after finishing the interruption function.
As this kind of the conventional technique, there is an apparatus disclosed in Japanese Patent Publication Laid Open (Kokai) No. Heisei 2-257224, “Linkage Edit Processor”. A linkage edit processor disclosed in the same publication deletes a redundant instruction for instructing the saving/return of a register when a register used at a function calling party (calling register) and a register used at a function called party (called register) are not in accord with each other, on the condition that there is no recursive call. Thus, edit processing to reduce the code size and shorten the execution time of a source program is optimized.
This optimization method of edit processing, in the normal function call, requires a code for providing a saving instruction of a calling register before a function call instruction and providing a return instruction of the saved register after the function call instruction, in order not to destroy the content of the calling register at the called party. Provided with a table for registering the call function information and the using register information, this method deletes unnecessary saving/return codes of a register which is not used at the called party, of the saved/returned registers of the function at the calling party, referring to the above table.
FIG. 7
shows a constitutional example of the conventional compiler which deletes the saving/return codes of an unnecessary register in the same way as the optimization method of edit processing disclosed in the Patent Publication No. 2-257224. The compiler shown in
FIG. 7
comprises an input unit
701
for receiving a source program to perform a lexical analysis, a syntax analysis unit
702
for generating a syntactic tree after analysis of the syntax from a lexical array, an optimization unit
703
for optimizing the syntax tree, a code generation unit
704
for generating an intermediate code
712
based on the optimized syntax tree, a using register control table by function
705
for registering information on a call function and a using register, a using register extracting unit by function
706
for registering a call function name and a using register in every function into the using register control table by function
705
after analysis of the intermediate code
712
, and an output unit
708
for supplying an assembly program file
713
having the saving/return codes of a register which is not used at the called party deleted therefrom.
By reference to
FIG. 7
, it will be easily understood that the conventional compiler optimization method disclosed in the Patent Publication No. 2-257224 can be realized, in a compiler, by additionally providing the output unit
708
for deleting the saving/return code of a register which is not used at the called party, of the saved/returned registers of the function at the calling party, referring to the using register control table by function
705
and the using register extracting unit by function
706
which supplies the information to the same table, after the code generation unit
704
of a general compiler.
This time, the conventional optimization method of a compiler will be described with reference to FIG.
7
and
FIG. 6
showing an example of the source program
711
. With reference to the portion corresponding to the intermediate code
712
supplied by the code generation unit
704
, in the source program shown in
FIG. 6
, there is a saving code of the registers “g”, “h” used by the function f
6
, before a call function for the function f
5
existing within the function f
6
, and there is a return code of the registers “g”, “h” used by the function f
6
, after the call function for the function f
5
.
According to the input intermediate code
712
, the using register extracting unit by function
706
recognizes the definition of the function f
6
and registers the function name f
5
called from the function f
6
and the register names “g”, “h” used by the function f
6
into the using register control table by function
705
. Next, it recognizes the definition of the function f
5
and registers the register name “f” used by the function f
5
into the using register control table by function
705
.
The output unit
708
recognizes that no overlapped register name is found between the registers “g”, “h” used by the function f
6
and the register “f” used by the function f
5
, with reference to the using register control table by function
705
. Then, a saving code of the registers “g”, “h” before the call instruction for the function f
5
and a return code of the registers “g”, “h” after the call instruction for the function f
5
are deleted, thereby to supply the assembly program file
713
.
The above-mentioned conventional optimization method of a compiler, however, cannot delete the saving/return codes of a register as for a function branching from certain address of a program, like an interruption function.
This is why an interruption function having no function at the calling party will not destroy the content of a register in use at the occurrence time of an interruption of a device; although it is necessary to provide a saving instruction of a register at the head of the interruption function corresponding to a function called party and provide its return instruction at the end of the interruption function, the using register information of a function at the calling party is required in order to delete these saving/return codes; therefore, unnecessarily saved/returned register cannot be detected.
Referring to
FIGS. 6 and 7
again, since the function f
6
is an interruption function, saving of a register and return of a register are performed respectively at the head and at the end of the function f
6
and a register in use at the occurrence time of an irregular interruption is not clear. Therefore, all the registers are saved at the head of the function f
6
and all the registers are returned at the end thereof.
The conventional output unit
708
deletes the saving/return codes of a register not in use at the called party, from the saving/return codes of the calling register, in the using register control table by function
705
. Therefore, the saving code of all the registers at the head of the function f
6
and the return code of all the registers at the end of the function f
6
cannot be deleted.
As mentioned above, the conventional compiler and the conventional optimization method thereof is defective in that the saving/return codes of a register cannot be deleted in a function branching at certain address of a program, like an interruption function.
SUMMARY OF THE INVENTION
In order to solve the above conventional defect, an object of the present invention is to provide a compiler and its optimization method improved in processing efficiency by deleting saving/return codes of an unnecessary register at the code output time of an interruption function.
According to the first aspect of the invention,
Chaki Kakali
Das Chameli C.
NEC Corporation
Scully Scott Murphy & Presser
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