JPH08123692A - Method and device for register allocation - Google Patents

Abstract

PURPOSE: To provide the register allocating method for generating a compact object program with good execution efficiency and a compiler device which has a function like it. CONSTITUTION: A selection allocation request is set in register information of an intermediate code first (step S1), and an operand register allocating process for the intermediate code is performed (step S2). Then it is checked whether or not a register is allocated to an operand regarding the selection allocation request (step S3) and when the register is allocated, a corresponding work register is not allocated. When no register is allocated to the operand regarding the selection allocation request, the work register is allocated (step S4). Thus, the allocation of an unnecessary work register is omitted to simplify the generated object program.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compiler, and more particularly to a register allocation method for generating an object program (object program).

[0002]

2. Description of the Related Art In an information processing device such as a microprocessor, a compiler device interprets a source program and translates it into a machine language target program. At this time, in many cases, the source program is once converted into an intermediate code (intermediate language) written in an intermediate language, and the target code is generated from the intermediate code. When the target code is generated from the intermediate code, the code is optimized and register allocation is performed as necessary.

In the register allocation process in the compiler device, based on the register allocation request information required for object expansion created for each intermediate code,
The type and number of registers that can be used are assigned to the intermediate code that appears.

Within one intermediate code, more registers (temporarily referred to as working registers) temporarily used for object expansion are required when the operand is not loaded than when the operand is loaded in the register. There are many things to do.

However, it cannot be determined whether or not the operand is loaded on the register unless the register allocation processing is actually performed. Therefore, information satisfying both the case where the operand is loaded in the register and the case where the operand is not loaded is passed to the processing unit that performs the object expansion as the register allocation request information. That is, the type and number of work registers required when the operand does not fit in the register are required.

[0006]

In the conventional register allocating process based on the register allocating request information as described above, even when the operands are loaded in the registers, the same number of working registers as those when the operands are not loaded are secured. To be done. That is, unnecessary work registers are additionally allocated.

As the number of allocated and secured registers increases, the probability that the value of the register will be saved in the memory when the object program is executed will increase. As the number of occurrences of evacuation processing increases, the object size increases,
The execution speed of the target program decreases.

Therefore, in the conventional register allocating process, there is a lot of waste in register allocating the working registers, and there is a problem that an optimum object program cannot be generated.

An object of the present invention is to provide a register allocating method for generating a compact and efficient execution target program in a compiler apparatus, and a compiler apparatus having such a function. More specifically, the purpose is to prevent unnecessary work register allocation.

[0010]

FIG. 1 is a flowchart showing the principle of register allocation processing of the present invention. FIG.
When the processing is started in step 1, first, a selective allocation request for allocating the register to one of the operand of the intermediate code and the work register corresponding to the operand is set in the register information of the intermediate code (step S1), and the intermediate code The operand register allocation processing is performed (step S2).

Then, it is checked whether or not a register is allocated to the operand related to the selective allocation request (step S3), and if the register is allocated, the corresponding work register is not allocated. If a register is not allocated to the operand related to the selective allocation request, the work register is allocated (step S4).

The register information is register allocation request information created for each intermediate code, and the selective allocation request is set by a flag, for example. Also,
At this time, the identifier of the operand related to the above selection allocation request is set as the request information of the work register.

[0013]

Before the register allocation is performed on the operand register and the work register, the selection allocation request is set in the register information, and then the operand register allocation processing is performed. In this operand register allocating process, register allocating process is performed on the operands related to the selective allocation request or the operands not related to the selective allocation request.

If a register is allocated to the operand related to the above selection allocation request, the register is not allocated to the corresponding work register. This makes it possible to reduce the number of registers to be allocated in the intermediate code that does not require a work register when registers are allocated to operands. Therefore, the registers are efficiently used and the data saving process is reduced.

If a register is not allocated to the operand related to the above selection allocation request, the register is allocated to the corresponding work register. In other words, when a register is assigned to an operand, a work register is not needed, and when a register is not assigned, a work register is needed. Will be assigned.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. The compiler apparatus of this embodiment first interprets a source program for a microprocessor having a plurality of real registers, and expands it into an intermediate code. Next, a register is allocated to the obtained intermediate code and expanded into a target code (object code) to generate a target program described by machine instructions.

FIG. 2 is a flow chart of a process of creating register allocation request information by the compiler apparatus of this embodiment. This process is performed for each intermediate code. The register allocation request information is the type, number, and operand information of the registers necessary for object expansion. For each intermediate code from the object skeleton that specifies the type and chunk of the intermediate code according to the length of the operand, etc. Created in. The compiler device performs register allocation processing based on the created register allocation request information.

When the processing is started in FIG. 2, it is first determined whether or not the number of work registers required by the intermediate code to be processed varies depending on the result of register allocation to the operand of the intermediate code (step S11). . If it changes, the selection allocation request is set in the register allocation request information (step S12). If it does not change, the selection allocation request is not set.

The selective allocation request is a register allocation request indicating that the work register is unnecessary when the register is allocated to the operand of a certain intermediate code, and the work register is necessary when the register is not allocated. . In other words, it is request information for allocating a register to either the operand or the work register.

FIG. 3 shows a concrete example of the compilation process of the source program. In FIG. 3, COMPUT
After the arithmetic processing of EA = B + C is converted into the intermediate code ADD, a series of object codes shown after --ADD-- are generated. Where ADD is COMPUTE
It is a label of the intermediate code corresponding to A = B + C.

Of the register allocation request information relating to the generated intermediate code ADD, the selective allocation and request register information is as shown in FIG. 4, for example. In FIG. 4, OPD1 represents an operand that stores the result of addition, and OPD2 and OPD3 represent operands that are added. Working represents the working register required by this intermediate code. OPD1 requests the register indicated by REG, and OPD2 and OPD3 do not request a specific register. Also, one 8-byte register is required as a working register.

The flag is an information flag indicating whether or not the selective allocation request is set. For example, when the flag is ON, it represents the selective allocation request, and when it is OFF, it represents the register request other than the selective allocation request.

Here, since whether or not the registers are allocated to OPD1 and OPD2 is not related to the necessity of the work register, these flags are OFF. On the other hand, when the register is allocated to the OPD 3, the work register becomes unnecessary, and when the register is not allocated to the OPD 3, the work register is necessary. That is,
Since the register may be allocated to either the OPD3 or the work register, ON is stored in the flag of the OPD3, and the identification number 3 of the OPD3 is stored as the flag of the work register.

As described above, the selection allocation request is set by turning on the flag of the operand that determines the necessity of the work register and storing the identifier of the operand as the flag of the work register. This is Figure 2
This corresponds to the process of step S12.

FIG. 5 is a flow chart of register allocation processing by the compiler apparatus of this embodiment. This process is also performed for each intermediate code as in the process of FIG. When the processing is started in FIG. 5, the operand register allocation processing is performed for each operand of the intermediate code to be processed while referring to the register allocation request information (step S21), and as long as there is the next operand (step S21). S22, YES), and this is repeated.

When the next operand is exhausted (step S
No. 22, No), the work register allocation process is performed for each work register with reference to the register allocation request information (step S23). As long as there is a next work register (step S24, YES), repeat this,
If the next work register is exhausted (step S24, N
O), the process ends.

Next, referring to FIGS. 6 and 7, FIG.
The operand register allocation processing and the work register allocation processing of will be described in detail. FIG. 6 is a flowchart of the operand register allocation process of this embodiment.
In the operand register allocation process, first, the register state table is referred to check whether or not there is already a register that holds the value of the operand being allocated (step S31).

The register status table is a table for holding the current allocation status of registers. For example, when a register is assigned to the operand of the intermediate code that is processed before the intermediate code that is the current processing target, the state of the register is the usage state and the contents correspond to it. It is written in the register state table that it is the contents of the operand. Therefore,
By referring to the register status table, it is possible to know whether or not the operand under allocation processing already exists in the register.

If a register holding the value of the operand exists, the register is allocated to the operand being allocated (step S32), and whether the selective allocation request is set to the operand in the register allocation request information. Check whether (step S3
3). If it does not exist, the process of step S33 is immediately performed.

When the selective allocation request is set to the operand during the allocation processing, information of the processing result of the operand (selective allocation target operand) is created (step S34), the processing is terminated, and the selective allocation request is made. If is not set, the process ends as it is.
The information on the processing result of the selective allocation target operand may be stored in the register state table.

If there is no register for holding the value of the operand being allocated in step S31 and the register is not allocated, the work register required because the operand was not loaded in the register in step S34. Create the information that the allocation of is always performed.

If there is a register for holding the value of the operand being allocated in step S31 and the register is allocated in step S32, step S34
Then, the information indicating that the unnecessary work register is not allocated because the operand is loaded in the register is created.

For example, in the case of the register allocation request information of FIG. 4, since the selective allocation request is set in the OPD3, the processing of step S34 is performed in the processing of the OPD3, and the created information is the next work register. Passed to allocation process.

FIG. 7 is a flow chart of the work register allocation process of this embodiment. In the work register allocation process, first, in the register allocation request information,
It is checked whether or not the selective allocation request is set in the work register during the allocation process (step S41).

If the selective allocation request is set, then the processing result of the corresponding selective allocation target operand created by the operand register allocation processing is referred to, and the register is allocated to the selective allocation target operand. It is checked whether or not there is (step S42).

If it is informed that a register is not allocated to the operand to be selectively allocated and that a work register being allocated is needed (step S42,
No), the register is allocated to the work register (step S43), and the process is terminated.

When a register is allocated to the operand to be selectively allocated and it is informed that the work register under allocation is no longer needed (step S42, Y).
ES), the process is terminated without assigning a register to the work register.

When the selective allocation request is not set in step S41, the register allocation processing for the requests other than the selective allocation request is continued (step S44). The work register allocation request other than the selective allocation is set, for example, when it is necessary to unconditionally secure the work register regardless of whether the register is allocated to the operand. In this case, the register is assigned to the work register without referring to the processing result of the operand.

For example, in the case of the register allocation request information of FIG. 4, since the identification number 3 of the operand OPD3 for selective allocation is set in the flag of the working register, the selective allocation process is performed for this working register. It is performed (step S41, YES). Where OPD
Referring to the processing result of step 3 (step S42), OPD3
If the register is allocated to the work register, the register is not allocated to the work register. If the register is not allocated to the OPD 3, the register is allocated to the work register (step S43).

In FIG. 4, when the flag of the work register does not store the identification number of any operand and the flag is OFF, the selective allocation request is not set, so that, for example, unconditionally. Registers are assigned to the work registers (step S44).

As described above, by providing the special information flag in the register allocation request information and setting the selective allocation request, the register can be allocated to only one of the operand related to the selective allocation request and the working register. .

Although FIG. 4 shows an example of register allocation request information, the present invention is not limited to this.
The register allocation request information having another configuration may be used.
For example, two working register flags may be prepared, one indicating whether or not a selective allocation request is set, and the other storing the identification number of the corresponding selective allocation target operand. it can.

[0043]

According to the present invention, it becomes possible to selectively allocate a register to only one of the operand and the working register in the register allocation process of the intermediate code by the compiler. As a result, the number of work registers to be allocated can be adjusted. By omitting unnecessary work register allocation processing, the size of the target program is reduced and its execution speed is improved.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a flowchart of a register allocation request information creation process according to the embodiment of this invention.

FIG. 3 is a diagram showing an example of compilation.

FIG. 4 is a diagram showing an example of register allocation request information in the embodiment.

FIG. 5 is a flowchart of register allocation processing according to the embodiment.

FIG. 6 is a flowchart of an operand register allocation process.

FIG. 7 is a flowchart of work register allocation processing.

[Explanation of symbols]

 OPD1, OPD2, OPD3 operands

Claims (9)

[Claims] 1. A method of allocating a register to an intermediate code in the process of converting a given source program into an intermediate code and generating an object program from the intermediate code, the method comprising: A selection allocation request for allocating a register to one of the corresponding work registers is set in the register information of the intermediate code, a process for allocating a register to the operand is performed, and it is checked whether a register is allocated to the operand. If the register is allocated to the operand, the register allocation method is characterized in that the register is not allocated to the work register. 2. The register allocating method according to claim 1, wherein a register is allocated to said work register if no register is allocated to said operand. 3. In the process of setting the selective allocation request, a first flag representing the selective allocation request is stored in a position corresponding to the operand in the register information, and is stored in the work register in the register information. The register allocating method according to claim 1 or 2, wherein a second flag indicating a selective allocation request is stored in a corresponding position. 4. The register allocation method according to claim 3, wherein an identifier of the operand is stored as the second flag. 5. The register allocating method according to claim 1, wherein it is checked whether or not a register is allocated to the operand by referring to information indicating a result of the register allocating process. 6. In a process for allocating a register to the operand, the register information is referred to check whether the selective allocation request is set to the operand, and if the selective allocation request is set, 2. The register allocation method according to claim 1, further comprising: generating information indicating a result of a register allocation process for the operand. 7. A method for allocating a register to an intermediate code in the process of converting a given source program into an intermediate code and generating an object program from the intermediate code, wherein a selective allocation request for the intermediate code is issued. A register allocating method characterized by setting the register information in an intermediate code and allocating a register to one of the operand and the work register according to the state of the operand. 8. A method of allocating a register to an intermediate code in the process of converting a given source program into an intermediate code and generating an object program from the intermediate code, the method comprising: , A register allocation processing method characterized by varying the allocation number of registers to be used temporarily. 9. An apparatus for converting a given source program into an intermediate code and generating an object program from the intermediate code, means for setting a selective allocation request for the intermediate code in register information of the intermediate code, A compiler apparatus comprising: a means for allocating a register to one of the operand and the work register according to the state of the operand.