JPH0816875B2 - Computer system emulation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer system emulation method, and more particularly to optimizing emulation for memory access.

[0002]

With the advent of new processors, higher performance computer systems are being produced. The biggest problem at that time is the inheritance of existing software. If all your existing software is written in a high-level language and you own all of its source code, you can recompile it to make it suitable for your new computer system. However, looking at the actual usage of commercial computers, it can be seen that general users have the source code.
There are few, and many programs cannot be easily converted because they are not necessarily written in high-level languages.

Therefore, emulation of a target computer system can be cited as an effective inheritance means of existing software. In this emulation method, the difference in processor architecture (instruction set) between the actual computer system and the target computer system and the hardware (I / O)
Different types of devices) and differences in control methods
By absorbing, it becomes possible to execute the program for any computer.

There are three methods for actually performing emulation: an interpreter method, a compile method, and a run-time compile method. The interpreter method takes out each instruction of a target processor, interprets and executes it, and it is easy to create an emulator. It is sufficient in terms of speed if the target computer system is realized by a microprogram. However, if realized on a normal processor,
It is difficult to obtain a practical speed.

The compile method is a method in which a target program is compiled in advance, and it is possible to apply a time-consuming compile technique in advance. Therefore, the actual execution time is the fastest among the three methods. You can However, since it is not possible to realize a program that changes a program, it is not possible to emulate a function of an OS loader or a program technique that uses self-modification. Furthermore, it is impossible to completely decompile binary code, so it is not possible to fully support a program in which all of the entry addresses cannot be statically traced. Furthermore, it has a drawback that the code size for emulation becomes large because all the code fragments that are unknown whether to actually execute it must be compiled.

On the other hand, the run-time compilation method requires an overhead for compiling, and
This overhead is further increased when complex optimization techniques are used in an attempt to improve the quality of the generated code. Therefore, the execution speed of the run-time compilation method becomes slower than that of the compilation method. However, since it becomes possible to emulate all target architectures (instructions and I / O), any program can be executed. This method has the highest practicality, and the present invention is also directed to this method.

The types of processor instructions are roughly classified into the following five types: -Memory operations (load / store of data) -Operations (integers, real numbers, tests) -Branches (conditional branches, unconditional branches)- System control (OS support) -Input / output No matter which of the above three emulation methods is used, the most time consuming process is the memory operation compared to the processing by the emulation target processor. . This is because the memory access operation is not limited to simple load / store of data, but is classified into the following four types of operations depending on the address (execution address) to be operated.・ Data load / store ・ Memory map I / O ・ Write to ROM area ・ Write to program area

When emulating a computer system using the memory map I / O, when the execution address of the load / store instruction is the I / O area,
It must operate as an input / output instruction. Also, the store in the ROM area must be disabled. further,
When using the run-time compilation scheme, writing to the program area (the already compiled area) invalidates the code and requires recompilation if the modified code is executed.

In principle, for every memory operation, it is necessary to test whether the execution address is the normal data space or not, which causes the emulation to slow down. 11 The memory operation test is as follows. Calculation of execution address if execution address> = start of I / O area and execution address <= end of I / O area then I / O processing if execution address> = start of ROM area and execution address <= end of ROM area then ROM processing if execution address> = program area start and execution address <= program area end then program processing

Therefore, there is a method of using an attribute table uniquely corresponding to all memory spaces (a method of giving 1 byte of attribute value to 1 byte of memory) (FIG. 1). The area to which the memory space belongs is recorded in the bit to be written in this attribute value (1 byte). The memory operation test using this is as follows. (Run-time compilation method) Execution address calculation Attribute address calculation Attribute value loading if attribute value is not 0 then if Program bit of attribute value is true then Program processing if I / O bit of attribute value is true then I / O Process if ROM value of attribute value is true then ROM process endif One byte of memory has one byte of attribute in order to speed up calculation of attribute address and speed up each test of attribute value. The compile method does not target the program processing, so its test is not necessary. Since most memory operations are normal data accesses (because the attribute value is 0), each bit of the attribute value is not tested during execution, so that the execution time is accelerated. This attribute method makes the run-time compilation method practical at a practical speed.

However, this memory manipulation remains the bottleneck of the overall emulation. The reasons are as follows. (1) Most memory operation instructions are used only for loading / storing data, and are rarely used for I / O processing, writing to the ROM area, and rewriting programs. . (2) Memory operation instructions are relatively frequently used instructions, and compared with the processing time of the test part, the original processing of loading / storing data is very small, so the relative speed decreases. The ratio of will increase. (3) Since each step of the processing of this test part depends on the result of the previous step, the steps cannot be executed in parallel at all. Due to this, it is not possible to expect speed improvement in a processor capable of executing instructions in parallel such as the super-scalar method (RS6000) and the VLIW method in parallel. (4) The load time of the memory is longer than that of a normal instruction. This method causes the execution pipeline to stall because the attribute value must be tested immediately after loading. This reduction in speed is a problem because current processors rely on this pipeline technology for execution speed. (5) Unless the code for the attribute value test is generated inline, the execution speed is reduced, and the entire compiled code becomes large. This also lowers the instruction cache utilization rate and increases page faults, thus reducing the overall processing efficiency.

As a patent document related to the present invention, there is JP-A-2-5138. This holds the attribute value as it is, as described above.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to optimize the emulation of memory access to speed up the entire emulation.

[0014]

The present invention is based on the conventional method of speeding up by having an attribute table corresponding to one byte of memory, and most of the memory operations are for loading / storing data. Focusing on the fact that it is used, most memory operation instructions can be executed without testing the attribute value.

A segment prediction table is added for this purpose (FIG. 2). That is, as shown in FIG.
The memory space is divided into groups of a certain size (called segments), 1-bit data (segment prediction bit) that expresses the logical sum of the attribute values of each segment is generated, and the prediction of that segment is also performed. The bit is ORed with the prediction bit of two adjacent segments. The operation is executed for all memory spaces to generate a segment prediction table (Fig. 2).

When the value of the bit stored in this segment prediction table is 0, it means that any of the memories belonging to the segment corresponding to the prediction bit is a memory for normal data. Yes, meaning that testing of each attribute is not required.

Instead of directly using the data of this segment prediction table, the category prediction flag is set to the CPU.
Keep this inside and refer to this flag. Since the category prediction flag has a different span to be inspected for each category of memory reference, the method of flag generation also depends on the span. This category prediction flag is 0
If so, the memory operation instruction of that category does not require the attribute test.

The test algorithm for the memory operation instruction is as follows. Execution address calculation if Category prediction flag = not 0 then attribute address calculation Load attribute value if if attribute value is not 0 then if Program bit of attribute value is true then Program processing if I / O bit of attribute value is true then I / O processing if ROM bit of if attribute value is true then ROM processing endif endif

As a criterion for selecting a category, it is preferable that the value of the base address used in the calculation expression of the addressing mode is not changed so much that the offset is a constant instead of the register. The following are examples of categories that can be actually used. -Access to stack variables (Fig. 3) -Access to global variables (Fig. 4) -Access to structures in the heap area (Fig. 5)

Access to a stack variable is often performed by using a stack pointer (SP) as a base register and a displacement as a constant value. Therefore, it is possible to make this a category. Access to global variables is based on the base register and displacement is often accessed as a constant. Furthermore, even in the heap area, it is possible to make it a category for each access to the same structure member.

When adding this method to the original attribute method, the overhead is the overhead of the category prediction flag test and the category prediction flag update necessary at the time of execution. There are two overheads incurred due to the testing of category prediction flags at runtime. -Instruction execution time required to test the prediction flag-Pipeline delay time caused by the branch of the test

In this method, the category prediction flag is CP.
Since it is held inside U, it is not necessary to load it from memory. When implemented as one bit in a register, two instructions, a test instruction and a conditional branch instruction, are overhead for testing the category prediction flag. Depending on the architecture of the CPU that is trying to execute the emulation, if it can be realized as one bit in the condition code register, only one conditional branch instruction will be the execution time of the instruction required for the test. Moreover, the probability that the memory operation instruction is used as an operation of data, that is, the probability that the prediction is correct is very high, and in this case, the attribute test is omitted. Since more instructions are required for attribute testing than for prediction flag testing, this method reduces the number of executed instructions.

The overhead due to pipeline stall caused by the latter test branch is the overhead that occurs only when the prediction is successful, and is totally irrelevant when the prediction is not successful. further,
If the prediction is correct, the pipeline delay due to the branch of the attribute test that was originally necessary can be eliminated,
Overall, there is no overhead at all.

Further, in the above-mentioned method, if the attribute value test is not expanded inline in the generated code,
Although the execution efficiency has decreased, using this method does not reduce the execution speed even if the generic value test is made into a subroutine, so the code size can be reduced and the instruction cache utilization efficiency is also improved. Further, since the calculation of the execution address and the test of the category prediction flag have no dependency relationship, parallel execution is possible in a processor having an architecture capable of executing instructions such as superscalar and VLIW in parallel.

Update of the category prediction flag, which is another overhead, is performed at the following two timings. -When the attribute of the target segment is changed-When the target segment of the category becomes another segment

The former occurs when code that has not been executed so far is executed for the first time. Emulation by the run-time compilation scheme compiles the code the first time it is executed, which changes the attribute values of the compiled memory. I / O and RO
The space of M is fixed and does not change during execution. Originally, the run-time compilation method uses a lot of processing time for compilation, so the overhead of updating the segment prediction table is much smaller than that. The latter happens when the address of the category's base register is changed. The overhead for this is caused by the following two steps. -Mask the lower bits of the address of the base register-Subtract the segment prediction bit This overhead is similar to the overhead of loading the attribute value, and if the target memory manipulation instruction is for data manipulation, Almost no overhead. Furthermore, once determined, the category prediction flag is reused, resulting in no overhead at all.

This method is for accelerating the runtime compiler method, but if the existing compiler optimization technology (data flow analysis) is used, this method can be more efficiently applied. It will be possible. Thereby, updating of the segment prediction flag can be minimized.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to IBM of International Business Machines (IBM, trademark)
An example applied when emulating a PC with RS / 6000 (trademark of IBM) of IBM is also described.

The processing procedure for emulating the IBM PC on the RS / 6000 by the run-time compilation method is shown in FIG. Inte to try first
1/8086 processor (Intel and 8086 are trademarks of Intel Corporation in the United States, hereinafter referred to as 8086)
0 Convert to the address of the compiled instruction string of the processor.

If the execution address of 8086 has already been executed, there is an entry in the address correspondence table,
Since the corresponding RS / 6000 address is recorded, the emulation is executed by branching there. If the execution address of 8086 has not been executed yet, it is not registered in this address correspondence table, and in this case, the runtime compiler is activated. The range to be compiled is all that can be judged that the 8086 instruction is reachable. By making the compilation target as large as possible, it is possible to reduce the number of times the compiler is called at runtime. further,
By increasing the range of compilation, the range to which optimization is applied also increases, so that more efficient optimization can be executed. This method is also used in the optimization unit and the code generation unit in FIG.

The run-time compiler has 80
The 86 instruction sequence is converted into an RS / 6000 instruction sequence. 8
Not only one 086 instruction is converted into RS / 6000 number instructions, but 8086 number instructions may be converted into RS / 6000 number instructions. It is possible to generate optimized code by compiling several instructions together rather than compiling one instruction. The types of instructions compiled are as follows.・ Memory operation (data load / store) ・ Operation (integer, real number, test) ・ Branch (conditional branch, unconditional branch) ・ System control (OS support) ・ I / O

Of the types of these instructions, it is only the branch instructions that divide the range that is actually compiled.
Branch instructions are not all, either, and are instructions such as indirect branch instructions and return instructions that change the value of the program counter after execution depending on the value of data. The indirect branch instruction is a register indirect branch, or a branch instruction using a segment register (far call, far ju).
mp) and so on. In order to compile such an instruction, the compiler determines the branch condition and calculates the execution address of the branch destination, and then the instruction for branching to the instruction sequence for searching the address correspondence table at the beginning of the loop in FIG. Generate a column.

For branch instructions other than that, if the branch destination exists in the address correspondence table, the compilation of the path is stopped there, and another reachable 8086 instruction is compiled. If it does not exist in the address mapping table, the path is continuously compiled, and all the reachable paths are compiled, so that one run-time compilation is stopped.

For the above instruction types other than branch,
It does not control the compile area of the run-time compiler, but only processes instructions that are translated. For input / output instructions, a subroutine that emulates a corresponding device (display, keyboard, disk, etc.) is prepared, and a call instruction to the subroutine is generated to compile. In the case of the 8086 instruction that accesses the I / O space by register indirect, it is not possible to determine which device will be used until execution time. Therefore, a subroutine for allocating the device is prepared, and a call instruction to that subroutine is generated. I'll do it.

In IBM PC, all I / Os are I / Os
Memory-mapped I /
It uses a technique called O, which allocates I / O to a normal data space. As a result, not all I / Os are processed only by I / O instructions, but in all instructions that access memory, the influencing address (execution address, effective address) is I.
It is necessary to test whether memory space for / O or space for data and programs. The address of memory mapped I / O of IBM PC is A0000 (hexadecimal)
To 256 bytes from DFFFF to DFFFF (FIG. 7).

Also, ROM space (E0 in IBM PC is
Since writing from 00 (hexadecimal) to FFFF must be invalidated, a test of the write execution address is also necessary. (Figure 7)

In run-time compilation of memory manipulation instructions:
Whether the I / O space is accessed as described above, or ROM
You have to test if you are accessing the space and the store instruction has already been compiled and R
It is also necessary to test whether a part of the program converted into the S / 6000 object code is changed.

Since the instruction of 8086 can take a memory as an operand of an operation instruction, the above test is required for an instruction having a memory as an operand in addition to a memory operation instruction (load / store instruction). ROM space and I
Since the / O space is fixed and takes one area, it is easy to test, but it is difficult to determine whether an address is a compiled program or data. Therefore, in order to process these efficiently, the attribute table is used. (Figure 7)

The attribute table has an entry of 1 byte for each byte of the IBM PC memory. Although the bits used are not all in one byte, the data (attribute values) in this attribute table is accessed very frequently, so using several bits at a time saves memory, but emulation is possible. Not good for speeding up. Therefore, 1 byte, which is the fastest and smallest unit of access, is used as an entry in this attribute table.

The attribute values are used as shown in FIG. The attribute table is initialized at the start of emulation (system initialization in FIG. 6). IB as mentioned above
Since the ROM space and I / O space are fixed in MPC, the I / O bit and ROM bit of the attribute table entry corresponding to these address areas are set to ON, and all other bits are set to OFF. The initial value is Only the program bit changes the attribute value at execution time. The runtime compiler sets the attribute value program bit corresponding to all the addresses of the 8086 instruction converted into the RS / 6000 object code to ON. .

FIG. 8 shows a flow chart of a test at the time of memory read using this attribute value. In case of read, the test of ROM space and program space is unnecessary.
FIG. 9 shows a flow chart of the test at the time of memory write. In the case of writing, it is necessary to test the ROM space, I / O space, and program space. In the case of write, three tests are required, but if the attribute value is 0, each test is unnecessary. In an actual program, it is extremely rare that the program is changed or the I / O space or the ROM space is accessed, as compared with the frequency at which data is normally accessed. Therefore, there is not much difference in execution time between the read test and the write test.

As an addition to reduce the processing time of this test, the memory space is divided into segments of a certain size, and the logical sum of the attribute values of each segment is used for the calculation of two adjacent segments. A segment prediction table obtained by performing logical sum and logical sum is used. (If the value of the segment prediction bit is 0, it is not necessary to test each attribute.) The category prediction flag obtained by classifying the data of this segment prediction table according to the usage of the memory is RS.
/ 6000 flag register. Naturally, if this category prediction flag is 0, the attribute operation is not required for the memory operation instruction of that category.

The categories used by the 8086 processor are as follows. (1) Stack category SS: Constant (BP) (2) Global category DS: Constant (3) Heap category ES: Constant (BX) In 8086, access to a stack variable is made in a base segment (SS) in a stack segment (SS). BP) is used as a base register, and displacement is frequently accessed with a constant value. Further, generally, the BP is updated at the beginning of the subroutine and returned when returning. The prediction flag of this stack category makes it possible to optimize the memory test code required for accessing the stack variable in the subroutine.

The segment size of this method is 8086.
In order to effectively process the above architecture, it is set to 128 bytes (FIG. 10). The 8086 can access the stack frame within a range of plus 127 bytes minus 128 bytes in the case of a short offset using a BP (base pointer) as a base register. In emulating the 8086, since the category in which the present method can be used most effectively is access to variables in the stack frame, 128 is set as the segment size in the present method. It is possible to change this size to a larger one, but if a too large value is used, the program and data will be mixed in one segment, so the prediction will be incorrect and the effect of this method will be I can not get it.

When the short offset is used (most stack frames are accessed in this addressing mode), the area accessible by the BP register is the shaded portion of the memory space in FIG. The segment having the attribute corresponding to the address indicated by the BP register is Seg BP. Before and after this segment (Se
g BP-1 and Seg BP + 1) is an area larger than the memory area accessible by the BP register, and the segment prediction bit corresponding thereto can predict all the memory area accessible by the BP register. . The BPth entry in the segment prediction table is BP
The register value is right-shifted by 7 bits (divided by 128).

The access to the global variable of (2) is accessed only by a constant offset in the data segment (DS). Further, since most programs do not change the value of DS during execution, once the global category prediction flag is set, it is often unnecessary to update the global category prediction flag due to the change of DS.
Since the size of the DS is 64 Kbytes, it is necessary to set not only the 1-bit prediction flag in the RS / 6000 condition register but also the logical sum of 512 bits from the bit of the entry of the segment prediction table.

If there is at least one 1 in the calculated values of the logical sum, the result will also be 1. Therefore, the speed can be increased by testing whether the aggregated bit string is 0 instead of 1 bit. Since RS / 6000 is 32 bits per word, it is possible to predict the memory space of 8086 having a size of 4 Kbytes by loading the segment prediction flag for one word. That is, a segment prediction flag of 17 words may be loaded in order to predict 64 Kbytes. One extra word is needed instead of 16 words. When the DS has a halfway address in the middle of the prediction segment, one extra test is performed, and 64 Kbytes are completely tested. Can be guaranteed.

Updating the category prediction flag of this global category requires 17 times more data to be loaded from the memory than updating the stack category. However, in modern processors with pipelined data caches such as RS / 6000, consecutive address reads can be loaded without overhead. Further, the possibility of cache miss increases only about a couple of times, so that only a few times as many processes are required as a whole. Further, the category prediction flag of the stack category is updated as frequently as the subroutine call, and the global category is updated less frequently.

The structure category (3) accelerates the following two memory accesses. -Access to members of the same structure in the heap area-Access to array elements in the heap area When accessing the heap of the 8086, ES is often used as a segment register and BX register is used as an index register. The same addressing mode (ES: constant (BX)) is used for accessing I / O space
Since it is accessed in, it cannot be determined whether this is to access the data. However, since access to members of the same structure in the heap area and access to array elements in the heap area are considered to have the same property, the prediction flag is used with this as a category.

The example shown in FIG. 12 is a structure (PARENT) consisting of two data (CHILD1 and CHILD2) in the heap area.
), Each element is increased by one. In this example, if this method is not used, it is necessary to test the attribute value 5 times (5 from 1 to 5). These tests are completely omitted by this method. In the overhead using this method in this example, it is necessary to read the segment prediction flag for the heap category from the execution address of ES: 0 (BX) at the head of the MOV instruction of (2) in FIG.

Next, how to speed up the test for one memory access by using the segment prediction flag will be described. The RS / 6000 is a CPU having a superscalar architecture capable of simultaneously executing different types of instructions (branch, integer, fixed point). In addition, the RS / 6000 has a 32-bit condition code register that is freely available to the user, so it is possible to map different category prediction flags to each bit of this register, and test this. Only one instruction is needed for each. Since the instruction of this test can be executed in parallel with the instruction that calculates the execution address, R
On S / 6000, the execution time of the instruction testing the category prediction flag can be completely zero.

In RS / 6000, if the branch condition of the conditional branch instruction (in this case, the value of the prediction flag) is determined three cycles before the execution of the instruction, the branch of 0 cycle can be performed, that is, It has an architecture that can eliminate the pipeline delay caused by branching. In the present scheme, the value of the category prediction flag is determined, in most cases, long before it is tested. Therefore, by utilizing the characteristics of the 0-cycle branch of RS / 6000, it is possible to eliminate the delay time due to the branch that was necessary even when the prediction was successful.

The execution time of the memory operation instruction in the PC simulator operating on RS / 6000 is measured. The target memory operation instruction is to write the value of the AX register to the variable on the following 8086 stack frame. Since this is an instruction to store normal data, it will be executed when there is a prediction. mov ss: 8 (bp), ax ・ Execution time according to this method (2 cycles) Calculation of execution address (0 cycles) if prediction flag = 0 then call
Attribute processing (1 cycle) Data storage Total 3 cycles (4 instructions) ・ Execution time by attribute method (2 cycles) Execution address calculation (1 cycle) Attribute address calculation (2 cycles) Attribute value load (4 cycles) if attribute value is not 0 then call attribute processing (1 cycle) Data storage 10 cycles in total (7 instructions)

The processing time (to the data space) of the attribute value test takes 7 cycles when the attribute value hits the data cache, but in the present invention, it is practically 0 cycle. The execution time of the entire processing is 10 cycles, which is 3 cycles. If the attribute value has a cache miss, the difference will be very large. If the prediction is wrong (I /
O, program, ROM, etc.), RS / 600
There is no run-time overhead due to the zero cycle branch capability of zero. The number of instructions to be executed was originally reduced from 7 to 4 but is reduced to 4. This improves the utilization efficiency of the instruction cache. Further, since the attribute value is no longer accessed, the utilization efficiency of the data cache is improved. By these, further speeding up is obtained.

[0055]

As described above, according to the present invention,
The emulation can be sped up because it is easy to check whether it is the actual data area, which was conventionally done during memory access emulation.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a conventional example.

FIG. 2 is a diagram illustrating the outline of the present invention.

FIG. 3 is a diagram illustrating categories of memory access according to the present invention.

FIG. 4 is a diagram for explaining categories of memory access according to the present invention.

FIG. 5 is a diagram illustrating categories of memory access according to the present invention.

FIG. 6 is a flowchart explaining the overall operation of the embodiment of the present invention.

FIG. 7 is a diagram illustrating a main part of the above-described embodiment.

FIG. 8 is a flowchart illustrating an operation at the time of memory read access according to the above-described embodiment.

FIG. 9 is a flowchart illustrating an operation of the memory write access according to the above-described embodiment.

FIG. 10 is a diagram illustrating generation of a segment prediction table according to the above-described embodiment.

FIG. 11 is a diagram illustrating an operation at the time of accessing a stack variable according to the above-described embodiment.

FIG. 12 is a diagram for explaining the operation when accessing the structure of the heap area in the above-mentioned embodiment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-5138 (JP, A)

Claims (8)

[Claims] 1. An emulation method, wherein a first processor having a first instruction set is emulated by a second processor having a second instruction set, and an application for the first processor is executed by the second processor. Generating the memory space of the first processor in the memory of two processors; generating a first attribute table representing the attribute value of each memory location of the memory space; Performs a logical operation on the attribute value of a memory location in the subspace and allocates the first logical value when there is a memory location that requires special processing, and when there is no memory location that requires special processing Generating a second attribute table by allocating a second logical value; Each time the specified range of memory access of standing changes,
Referring to the second attribute table, a step of determining whether or not a memory location requiring special processing in addition to the memory access is within the range of the memory access, When it is determined that the location does not exist, the step of simply executing the memory access without performing the check by the above-mentioned first table until the range of the memory access is changed, and the memory requiring special processing. When it is determined that there is an access, at least until the next memory access range is changed, it is determined whether or not special processing is necessary by referring to the above-mentioned first table for each memory access. If so, the emulation method comprising the step of executing the special processing. 2. An emulation method, wherein a first processor having a first instruction set is emulated by a second processor having a second instruction set, and an application for the first processor is executed by the second processor. Generating the memory space of the first processor in the memory of the two processors, generating a first attribute table representing the attribute value of each memory location of the memory space, and changing the attribute value. A step of modifying the first attribute table; and, for each subspace of the memory space, performing a logical operation of the attribute value of the memory location in the subspace, and when there is a memory location requiring special processing, If you allocate a logical value of 1 and there are no memory locations that need special handling, The step of generating a second attribute table by allocating a logical value of 2; the step of modifying the second attribute table when the first attribute table is modified; and the specification of the current memory access range. Every time it changes
Alternatively, each time the second attribute table is modified, the second attribute table is referred to, and whether the memory location requiring special processing in addition to the memory access is within the range of the memory access is checked. The determining step, and when it is determined that there is no memory location that requires special processing, until the next change in the range of memory access or until the second attribute table is modified, 1 Memory is not used for inspection
When it is determined that there is a memory access requiring a special process and a step of executing the access, at least until the next memory access range is changed or the second attribute table is modified. Up to the step of determining whether or not special processing is necessary by referring to the first table for each memory access, and executing the special processing if necessary. 3. The emulation method according to claim 1, wherein the sub space is allocated to each of a series of segments that fills the memory space, and the sub space includes the segment and two segments adjacent to the segment. 4. The internal register of the second processor holds the result of determination as to whether or not the memory location requiring the special processing is within the range of the memory access. Emulation method. 5. The memory-mapped I is the special processing.
5. The emulation method according to claim 1, 2, 3 or 4, which is executed for an access to an I / O, a write access to a ROM area, and a write access to a program area. 6. The size of the memory access range changes according to the method of memory access.
The emulation method described in 2, 3, 4 or 5. 7. The emulation method according to claim 6, wherein the memory access method includes at least a stack variable access method, a global variable access method, and a heap area structure access method. 8. The second processor for emulating a first processor having a first instruction set with a second processor having a second instruction set to execute an application for the first processor on the second processor. Computer emulation for processor emulation
In the program product, the step of generating the memory space of the first processor in the memory of the second processor, the step of generating a first attribute table representing the attribute value of each memory location of the memory space, and the current memory・ Each time the access range is changed,
Alternatively, each time the second attribute table is modified, the second attribute table is referred to, and whether the memory location requiring special processing in addition to the memory access is within the range of the memory access is checked. Each time the determination step and the current memory access range specification changes,
Referring to the second attribute table, a step of determining whether or not a memory location requiring special processing in addition to the memory access is within the range of the memory access, When it is determined that the location does not exist, the step of simply executing the memory access without performing the check by the above-mentioned first table until the range of the memory access is changed, and the memory requiring special processing. -When it is determined that there is an access, at least until the next memory access range is changed, it is determined whether or not special processing is necessary by referring to the first table for each memory access, and it is necessary. If so, the emulation computer characterized by causing the second processor to execute the step of executing the special processing. Program product.