JP2005044017A - Microprocessor and compiler for program to be executed by microprocessor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microprocessor in which it is possible to quickly perform access to data and a compiler for a program to be executed by the microprocessor. <P>SOLUTION: This microprocessor 40 is provided with an instruction decoder 6 for decoding successively read instruction codes, and for generating a control signal, an address register 11 for storing and generating address information, an ALU 9 for performing various arithmetic operations and an internal RAM 7 for temporarily storing information. Address decode parts 7A, 7B and 7C of the internal RAM 7 are configured of a high order address decoder and a low order address decoder, and generates an overall address decode signal from a high order address decode signal and a low order address decode signal. In this case, delay until the low order address decode signal of the low order address decoder is derived is shorter than delay until the high order address decode signal of the high address decoder is derived. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microprocessor and a compiler that mainly execute programs written in a high-level language, and more particularly to a microprocessor that performs processing using a stack and a compiler for a program that is executed by the microprocessor.
[0002]
[Prior art]
When designing a program in a high-level language, arguments and return values for subroutines are exchanged on the stack, and for local variables in the C language, an area is secured on the stack and an operation is performed. For this reason, the operation with local variables is complicated by the occurrence of RAM (Random Access Memory) address operation and its read, storage address operation and its write. Further, when the access speed of the external RAM is low, the speed affects the overall processing speed. In order to increase the speed of subroutine execution processing, a method has been provided in which stack operations relating to subroutine call / return are parallelized and thus speeded up (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP 11-242595 A
[0004]
[Problems to be solved by the invention]
The method proposed in the above document is configured to increase the speed, but since the stack actually used is connected as an external memory, it is considered that access to the external memory is generally slow. If the processing contents frequently access the external memory, it is difficult to speed up the execution process. This document does not mention access to data on the stack and computation.
[0005]
Therefore, an object of the present invention is to provide a microprocessor capable of accessing data at high speed and a compiler for a program executed by the microprocessor.
[0006]
[Means for Solving the Problems]
A microprocessor according to an aspect of the present invention includes an internal memory that stores information accessed based on an address signal, an arithmetic unit that performs various operations including information using information in the internal memory based on an instruction, and an instruction to be given An instruction decoding unit that decodes a code and outputs control information for controlling each unit including an operation command based on the decoding result, and an address decoding unit that inputs and decodes given address information and outputs an address signal .
[0007]
The address information includes upper address information and lower address information. The delay from the input of the lower address information to the derivation of the address signal by the address decoding unit is from the input of the upper address information to the derivation of the address signal. Shorter than the delay.
[0008]
Therefore, the access to the partial area referred to based on the lower address information of the internal memory is performed faster than the access to the partial area referred to based on the upper address information. Access is possible. Further, it is possible to speed up the access of the partial area referred to based on the lower address information of the internal memory. For example, a large amount of data can be accessed at a high speed as compared with the conventional method of calculating using a register file.
[0009]
Preferably, the address decoding unit decodes the upper address information of the address information and outputs a higher decode signal, and the lower decoder which decodes the lower address information of the address information and outputs a lower decode signal And a generation decoder that inputs an upper decoding signal and a lower decoding signal to generate and output an address signal.
[0010]
Therefore, by providing a separate upper decoder and lower decoder in the address decoding unit, and further providing a generation decoder, the delay from the input of the lower address information to the derivation of the address signal is input to the upper address information. It is shorter than the delay until the address signal is derived.
[0011]
Preferably, the bit length of the lower address is shorter than the bit length of the upper address. Therefore, the low-order decoder can be configured easily, and the number of processing stages for decoding can be reduced.
[0012]
The above-mentioned microprocessor preferably further includes an address generation unit that generates upper address information, and the address generation unit converts the address register that stores the upper address information and the upper address information stored in the address register into the instruction decoding unit. The address update unit for updating based on the control information is included, and the lower address information is included in the control information output by the instruction decoding unit.
[0013]
Therefore, by updating the upper address information of the address register, an area accessed based on the lower address information of the internal memory, that is, a stack area that can be accessed at high speed can be variably set in the internal memory.
[0014]
Preferably, the above update is an increment or decrement of the address indicated by the upper address information.
[0015]
Preferably, access to the internal memory is performed in one cycle based on the lower address information output from the instruction decoding unit.
[0016]
The above-mentioned microprocessor further includes a program counter for holding information for sequentially designating instruction codes to be given to the instruction decoding unit, and instructs the instruction code given to the instruction decoding unit to branch to another processing routine When it is a code, the information held in the program counter is saved in the internal memory by the control information, the value of the program counter is changed to a specified value, and the contents of the address register are updated.
[0017]
Therefore, when branching to another processing routine, by executing one instruction code, the information held in the program counter is saved in the internal memory, the value of the program counter is changed to the specified value, and the address register It is possible to execute a series of processes for updating the contents of.
[0018]
Preferably, saving of the information held in the program counter to the internal memory, changing the value of the program counter to a specified value, and updating the contents of the address register are performed in parallel. Therefore, it is possible to quickly process a branch to another processing routine.
[0019]
Preferably, when an exception factor signal is input to the instruction decoding unit in the process, the contents of the address register and the program counter are controlled according to the control information in order to branch from this process to an exception factor processing routine prepared in advance. Is saved and the contents of the address register are changed to a predetermined fixed value.
[0020]
Accordingly, the contents of the address register and the contents of the program counter can be saved by one instruction code, and the contents of the address register can be changed to a predetermined fixed value, so that it is possible to quickly branch to the exception factor processing routine.
[0021]
Preferably, when an instruction code for returning from the branch destination processing routine to the original processing is given to the instruction decoding unit, the contents of the program counter are restored to the contents previously saved by the control information.
[0022]
Preferably, when the instruction decoding unit is given an instruction code for returning from the branch destination processing routine to the original processing, the contents of the address register and the contents of the program counter are restored by the control information.
[0023]
Therefore, the contents of the address register and the contents of the program counter can be restored by one instruction code, so that it is possible to quickly return to the original process from the branch destination processing routine.
[0024]
Preferably, the internal memory has three independent ports, reads information from the internal memory based on an address signal for the first port of the three ports, and the second of the three ports. The information is read from the internal memory based on the address signal for the other port, the read information is given to the operation unit, and the operation result is obtained as the address signal for the third port of the three ports. Based on the above, the operation of storing in the internal memory is performed in one cycle.
[0025]
Therefore, it is possible to execute arithmetic processing while referring to the internal memory at high speed.
Preferably, the instruction code includes lower address information for each of the address information for the three ports.
[0026]
Preferably, the instruction code includes constant information, and the instruction decoding unit sends the constant information to a bus for supplying information read from the internal memory to the arithmetic unit. Therefore, the bus can be shared for supplying the information referring to the internal memory and the constant information to the arithmetic unit, and the apparatus configuration can be simplified. Also, constant information can be given directly from the instruction decoding unit to the arithmetic unit, so that arithmetic using the constant information can be executed quickly.
[0027]
Preferably, when branching to an exception handling routine according to the occurrence of an exception factor during processing, the contents of the address register are saved and updated to a fixed value, a cycle for waiting time is executed, and the value of the program counter is saved To store in internal memory.
[0028]
Thus, when an exception factor occurs during processing, the contents of the address register are saved and updated to a fixed value. Even if an instruction that references internal memory is executed at the beginning of the exception processing routine at the branch destination, the cycle for the waiting time is executed at the time of branching, so the address register is changed and the contents after the change are changed. Based on this, the time required for the address decoding unit to generate the address signal is offset by the waiting time, and the appropriate area can be referred to using the updated address information in the subsequent internal memory reference.
[0029]
Preferably, when returning from the exception handling routine to the original process before branching, the address register is restored to the saved contents and a cycle for waiting time is executed.
[0030]
Thus, when returning to the original processing, the contents of the address register are changed. Even if the first instruction of the original process that was restored instructs to refer to the internal memory, the cycle for waiting time is executed at the time of return, so the address register is changed and the contents after the change are changed. Based on this, the time required for the address decoding unit to generate the address signal is offset by the waiting time, and the appropriate area can be referred to using the updated address information in the subsequent internal memory reference.
[0031]
A compiler according to another aspect of the present invention is a compiler that sequentially inputs source codes constituting a source program, converts them into instruction codes for the above-described microprocessor, and outputs an instruction code string. When the source code to be referred is converted, if conversion to an instruction code for instructing the change of upper address information is performed immediately before, the waiting cycle is performed before the instruction code of the source code in the instruction code string. Compile to put the instruction code.
[0032]
Since the instruction code for the waiting cycle is placed between the instruction code that changes the upper address information and the instruction code that refers to the internal memory, when executing the instruction code that refers to the internal memory, The time required to generate the address signal based on the updated contents after the upper address information is updated is offset by the waiting time, and the updated address information is used for subsequent internal memory references. You can refer to the area.
[0033]
Preferably, when a source code instructing a subroutine call is detected in the source program, the information stored in the program counter is saved in the internal memory, and the value of the program counter is changed to a specified value. Converts to an instruction code that instructs to update the register contents.
[0034]
Therefore, when a subroutine call is instructed, the information held by the program counter is saved in the internal memory by one instruction code, the value of the program counter is changed to the specified value, and the address is changed. You can command to update the register contents.
[0035]
Preferably, when a source code instructing the end of a subroutine is detected in the source program, the source code is converted into an instruction code for restoring the contents of the program counter to the contents saved in advance.
[0036]
Preferably, when the source code next to the source code instructing the subroutine call in the source program instructs to refer to the internal memory, the waiting time is set in the instruction code group instructing the return from the subroutine. Compile to put the instruction code for the cycle.
[0037]
Since the high-order address information is changed in order to return from the subroutine, the instruction memory for the waiting cycle is placed in the instruction code group instructing the return from the subroutine. In the case of referring, the upper address information is updated, and the time required to generate a signal for accessing the internal memory based on the updated contents is offset by the waiting time. Can refer to an appropriate area using the updated address information.
[0038]
Preferably, when it is detected in the source program that the first source code of the subroutine indicates an internal memory reference, an instruction code for a waiting cycle is placed in the instruction code string before the instruction code of the source code. Compile to
[0039]
Therefore, when the upper address information is updated in the immediately preceding subroutine and the internal memory is referred to at the beginning of the next subroutine, the upper address information is updated and the internal memory is accessed based on the updated upper address information. The time required to generate a signal for this purpose is offset by the waiting time, and in the internal memory reference, an appropriate area can be referred to using the updated address information.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0041]
(Embodiment 1)
In the present embodiment, the partial area of the internal RAM is made to function as a stack, and the circuit scale for accessing the stack area of the address decoder related to the internal RAM is reduced, so that the address data is decoded and a decode signal is generated (derived). A processor is provided that shortens the time (delay) required until the time.
[0042]
FIG. 1 shows a configuration of a microprocessor 40 according to the present embodiment. The microprocessor 40 is a port address output 1, data input 2 and data output 3, program counter (hereinafter abbreviated as PC) 4, pipe 5, instruction decoder 6, 3-Port RAM (hereinafter simply abbreviated as internal RAM) 7 , A bus 8, ALU (Arithmetic and Logic Unit) 9 for performing an operation (arithmetic / logical operation) using information in internal RAM 7 and an operation (arithmetic / logical operation) using information given from instruction decoder 6, B bus 10, an address register 11, incrementers 12 and 14, MUX (Multiplexor) 15 and 16, a data output buffer 17, a data input buffer 18, and a C bus 19. The internal RAM 7 includes a memory cell array 70 and address decode units 7A, 7B, and 7C on the A bus side, the B bus side, and the C bus side, respectively. Address decode units 7A, 7B and 7C receive and decode address information relating to access to memory cell array 70 given from the bus side, and output an address signal for accessing memory cell array 70 as a decoding result.
[0043]
A program executed in the microprocessor 40 includes a plurality of instruction codes and is stored in an external memory (not shown). Address data for accessing the external memory from the microprocessor 40 is connected to the address output 1, and data read from the external memory to the microprocessor 40 is connected to the data input 2 and written from the microprocessor 40 to the external memory. The data to be loaded is connected to the data output 3. Although the entire microprocessor 40 operates in synchronization with an external clock input, the illustration of the clock input and the description of the synchronous operation are omitted here.
[0044]
The PC 4 holds the address data in which the instruction to be fetched next is stored while performing the counting operation, and instructs the external memory via the address output 1. When an instruction code, which is data read from a designated address based on the designated address data, is input to the pipe 5 for adjusting the timing via the data input 2, it is given to the instruction decoder 6 through the pipe 5 as appropriate. Deciphered here. The other parts of the microprocessor 40 operate according to instructions from the instruction decoder 6 based on the result of decoding the instruction code.
[0045]
The ALU 9 has two input ports and one output port, and the RAM 7 has three independent ports (3-Port). The A bus 8 is a dedicated bus that outputs data in the internal RAM 7 to the ALU 9, and is connected to one input port of the ALU 9. The B bus 10 is a dedicated bus for outputting data from the external memory to the ALU 9 via the data input 2 and the data input buffer 18, and is connected to the other input port of the ALU 9 and simultaneously outputs data via the data output buffer 17. 3 is also connected. The C bus 19 is for input only, and is connected to the output of the ALU 9 and the PC 4. Here, it is assumed that the internal RAM 7 has a data width of 32 bits, an address data width of 16 bits, and a capacity of 64k words = 2M bits.
[0046]
The address register 11 is a register that holds the upper 11 bits of the 16 bits of address data in the internal RAM 7. The value held in the address register 11 is incremented or decremented by the instruction decoder 6 via the incrementer 12.
[0047]
One of the output of the address register 11 and the output of the incrementer 12 is selected by the MUX 16 and connected to the A bus address of the A bus 8. The output of the address register 11 is connected to the B bus address of the B bus 10 (not shown).
[0048]
One of the output of the address register 11 and the output of the incrementer 12 is selected by the MUX 15 and connected to the C bus address of the C bus 19. The lower 5 bits of the address data of the internal RAM 7 are independent at the three ports of the internal RAM 7, and a signal from the instruction decoder 6 is connected thereto. Therefore, the internal RAM 7 can be accessed in various ways according to the instruction code of the program.
[0049]
Here, assuming that the value held in the address register 11 (the value of the upper address data) is not changed, the accessible area of the internal RAM 7 is a range that can be specified by the lower address data, that is, 32 (= 2 ^ 5) words. Therefore, the internal RAM 7 can be accessed as if there were 32 32-bit internal registers, and various operations can be performed in the space according to the instruction code.
[0050]
If the value of the address register 11 is incremented by +1, the address of the internal RAM 7 is increased by 32, and the area of the internal RAM 7 that can be accessed (= the area where data can be read or written by the instruction code) is moved. Can be accessed for 32 words. The same applies when the value of the address register is set to -1.
[0051]
Now, it is assumed that the internal RAM 7 is realized by an SRAM (Static RAM). Each cell of the SRAM is shown in FIG. The SRAM cell 21 in FIG. 2 includes inverters 22 and 23 that hold 1-bit information supplied from a data line pair, and transistors 24-29. A word line WA to which a signal obtained by decoding the address of the first port among the three ports of the internal RAM 7 is supplied is connected to the transistors 24 and 25, and similarly, a signal obtained by decoding the address of the second port is supplied. The WB connected to the transistors 26 and 27 is connected to the transistors 28 and 29. Similarly, the WC to which the signal obtained by decoding the address of the third port is supplied.
[0052]
Of the word lines WA, WB and WB, only the selected word line goes high, and the transistor connected to the selected word line is turned on. When word line WA is selected, data line pair DA and DAb are connected to inverters 22 and 23 via transistors 24 and 25, respectively. Similarly, when the word line WB is selected, the data line pair DB and DBb are connected to the inverters 22 and 23 via the transistors 26 and 27, and when the word line WC is selected, the data line pair DC and DCc. Is connected to inverters 22 and 23 through transistors 28 and 29.
[0053]
The cells 21 are arranged as shown in FIG. 3 to form an SRAM. In FIG. 3, the decoded signal from the A bus address is decoded from the C bus address via the word lines WA0000 to WAFFFF, and the decoded signal from the B bus address is decoded from the C bus address via the word lines WB0000 to WBFFFF. A signal is given to each cell 21 through word lines WC0000 to WCFFFF. A corresponding data line pair is connected to the cell 21 connected to the selected word line and turned on.
[0054]
A sense amplifier AMP is arranged at each port of the SRAM (internal RAM 7), and the data held in each cell 21 is amplified by the sense amplifier AMP to be data DA00 to DA1F of the A bus 8 and data DB00 to DB1F of the B bus 10. , Output (read) as data DC00 to DC1F of the C bus 19, respectively.
[0055]
Similarly, when data is written, the value of the data line selected by the word line and driven from the sense amplifier AMP is written to each cell 21.
[0056]
FIG. 4 shows a configuration of an address decoding unit that generates a signal of each word line. The address decoding units 7A, 7B and 7C of the internal RAM 7 have the same configuration as shown in FIG. The address decoding unit has an upper address decoder 41, a lower address decoder 42 and an address decoder 43. The upper 11 bits A5 to A15 driven from the address register 11 are input to the address decoder 41, and decoding result signals GA000 to GA7FF are generated and applied to the address decoder 43. Of the signals GA000 to GA7FF, only the signal at the corresponding address is high, and the other signals are low.
[0057]
The lower 5 bits A0 to A4 driven from the instruction decoder 6 are input to the address decoder 42, and the decoding result signals GB00 to GB1F are generated and applied to the address decoder 43. Of the signals GB00 to GB1F, only the corresponding address signal is high, and the other signals are low.
[0058]
Further, the decoded signals are input to the address decoder 43, and individual word line signals W0000 to WFFFF are generated and output. Of the word line signals W0000 to WFFFF, only the word line signal at the corresponding address is high, and the other word line signals are low.
[0059]
Here, the address decoder is separated into a high-order address decoder 41 and a low-order address decoder 42, and the low-order address decoder 42 is realized by a relatively small circuit, for example, a one-stage circuit, and a subsequent-stage address decoder 43. Since the number of stages is reduced, the address decoding unit minimizes the time required (delay amount) from the input of the lower address data (data of the lower 5 bits A0 to A4) to the output of the word line signals W0000 to WFFFF. It can be.
[0060]
Assuming that the microprocessor 40 is operated with a clock of 100 MHz, one cycle is 10 ns, but decoding is performed from the change of the lower address data (lower 5 bits A0 to A4 data), and the decoding result is output. Furthermore, it is assumed that the timing design is performed using the decoding result so that the delay (time required) until data is read from the SRAM cell is within one cycle. In the microprocessor 40 designed in this way, when only the lower address data (data of the lower 5 bits A0 to A4) changes, various data can be calculated in one cycle, and the register operation is performed by a conventional general-purpose register machine. The calculation can be performed in the same manner as.
[0061]
Using this microprocessor 40, a source program 50 (hereinafter simply referred to as program 50) written in the C language of FIG. 5 is executed. At the time of execution, it is assumed that the program 50 is precompiled and converted (translated) into machine code executable by the microprocessor 40.
[0062]
The program 50 is a subroutine program of the function func1, has variables a and b as arguments, and has local variables c, d and e. The program 50 of the function func1 is executed when called from another function program (not shown). In addition, a subroutine program of another function func2 is called in the function func1 of the program 50. The subroutine program of the function func2 takes a variable c as an argument and has a local variable f.
[0063]
An example of the arrangement of data on the internal RAM 7 when the program 50 is executed is schematically shown in FIG. 6, and the operation of the microprocessor 40 for each cycle is shown in a table form in FIG. FIG. 7 shows a source line number 71 indicating the line number assigned to the left end of the program 50 of FIG. 5 and a mnemonic that is a machine code obtained by compiling the source code described in the line of the source line number 71. A code 72, an operation 73 of the microprocessor 40 when executing the mnemonic code 72, and a cycle number 74 indicating the order of cycles in which the mnemonic code 72 is executed are shown.
[0064]
When the function func1 is called from another function not shown and the program 50 is executed, the value of the address register 11 is 0, and the variables a and b to be copied to the argument of the function func1 are the addresses “00h + 2” of the internal RAM 7. Assume that the addresses are stored in the address “00h + 1”.
[0065]
First, since it is necessary to copy the argument to the stack, in the first and second cycles indicated by the cycle number 74, the contents of the local variable area which is the area of the internal RAM 7 specified by the data in the current address register 11 are Copy to the area specified by (the value of the address register 11 + 1) which is the local area used by the function func1 to be executed next. At this time, the value of the address register 11 becomes the upper address for the A bus 8 and (value of the address register 11 + 1) becomes the upper address for the C bus 19, and copying is performed between areas of different upper addresses. As a result, the variables a and b are copied to the addresses “20h + 1” and “20h + 2”, respectively.
[0066]
In the third cycle indicated by the cycle number 74, the next function uses the return address (PC + 4) when the processing of the function func1 is completed by executing the mnemonic code 72 of the call instruction of the subroutine (function func1). The operation of saving to the local area to be performed, incrementing the value of the address register 11 by 1, and substituting the start address of the function func1 into the PC 4 to transfer the control to the function func1 can be executed in parallel. Therefore, since subroutine calls can be executed in one cycle, subroutine calls can be processed at high speed.
[0067]
The compiler assigns the areas of local variables c, d, and e of the function func1 to addresses 3, 4, and 5, respectively, of the local area (see FIG. 6). The first instruction in the function func1 is an arithmetic instruction “c = a + b;” and is an instruction accompanied by an operation referring to the internal RAM 7. At this time, when the function func1 is called first, the value of the address register 11 has changed. If the delay amount from the higher address is large, the operation instruction may not be completed in one cycle. Therefore, a mnemonic code 72 ('NOP') indicating an instruction that does not perform anything in the fourth cycle indicated by the cycle number 74 is inserted by the compiler to prepare for an operation on the next local variable, that is, an operation of “c = a + b;”. . When the instruction decoder 6 inputs the instruction code and interprets it as “NOP”, the instruction decoder 6 does not operate in the cycle assigned for the instruction code and waits until the next instruction code is input. In the “NOP” cycle, all the internal buses and control signals are not changed and the current state is maintained.
[0068]
Here, the purpose of inserting the instruction code ('NOP') will be described. In the microprocessor 40, the delay time from the input of the upper address data to the decoding and deriving of the decode signal is relative to the delay time from the input of the lower address data to the decoding and deriving of the decode signal. It becomes long. If the delay time (required time) from input of address data to decoding of the decode signal is long, access (reference) to the internal RAM 7 may not be completed in one cycle, and data for the next operation instruction may not be read. There is. In other words, “access time” = “address decoding delay time” + “memory cell read time (word line / bit line delay and sense amplifier delay)”. The time will be longer. Even if the access time takes 1 cycle or more (10 ns or more at 100 MHz), the instruction code ('NOP') is executed for one cycle immediately before the next operation instruction, so that an extra 1 for the access time. The cycle data can be allocated, and the operand data can always be successfully accessed when the next operation instruction is executed. As a result, it is possible to reliably avoid an error state in which an operation instruction cannot be executed without obtaining necessary data.
[0069]
Calculations between local variables are performed in the fifth and sixth cycles indicated by cycle number 74. Since all the variables (operands) for these operations are assigned to the same upper address area, they all end in one cycle.
[0070]
Since the function func2 is to be executed next, the argument c is copied to the local area (address “40h + 1” in FIG. 6) used in the function func2 in the seventh cycle indicated by the cycle number 74. In the eighth cycle shown in FIG. 6, the return address of PC4 is saved (copied to the address “40h + 0” in FIG. 6), the address register 11 is carried up, and the start address of the function func2 for PC4 is assigned simultaneously. Control is transferred to the function func2.
[0071]
In the ninth cycle of cycle number 74, the upper address is delayed by the mnemonic code 72 ('NOP') inserted by the compiler as in the fourth cycle.
[0072]
In the tenth cycle of cycle number 74, an operation instruction (f = c + 1;) with local variables and constants is executed. Information on the constant (= 1) for this calculation is included in the corresponding mnemonic code 72, and the constant information is given to the ALU 9 by driving the B bus 10 by the instruction decoder 6 and executed. Therefore, the B bus 10 can be used for transferring data read from the internal RAM 7 to the ALU 9 and for transferring constant information from the instruction decoder 6 to the ALU 9.
[0073]
Since the process of the function func2 is completed and the process returns to the process of the function func1, the value of the address register 11 is decremented by -1 in the 11th cycle indicated by the cycle number 74, and the return value is returned in the 13th cycle indicated by the cycle number 74. Copy to the local area used in the original function func1, restore the value of PC4 in the 14th cycle of cycle number 74, and return to the control of the function func1. Thus, since the value of the address register 11 is changed when returning from the subroutine (returning from the function func2 to the original function func1), it is necessary to wait for a delay of the higher address, and the twelfth cycle indicated by the cycle number 74 Then, the mnemonic code 72 ('NOP') inserted by the compiler is executed.
[0074]
In the fifteenth cycle indicated by cycle number 74, an operation between local variables is performed, and a process for returning (returning) to another function (not shown) that called function func1 in the sixteenth to nineteenth cycles is performed. It is. At this time as well, since the value of the address register 11 is similarly changed, the mnemonic code 72 (“NOP”) indicating the instruction to be inserted inserted by the compiler is executed.
[0075]
In the operation 73 of the subroutine call instruction ('CALL func1', 'CALL func2') in FIG. 7, in this one cycle (one cycle of the clock), "saving the contents of PC4" and "carrying up the value of the address register 11" The three operations of “PC4 value update” are simultaneously performed in parallel. Conventionally, since there is no thing corresponding to the “address register”, “saving of PC contents” and “update of PC value” may be processed sequentially or may be processed simultaneously in parallel. The present embodiment has a feature that parallel processing is performed simultaneously including “carrying up the address register 11”.
[0076]
This simultaneous parallel processing will be described with reference to FIG. “Saving the contents of PC4” is performed using the path “PC4 → incrementer 14 → C bus 19 → internal RAM 7”. The “carrying up of the address register 11” is performed using the path “address register 11 → incrementer 12 → address register 11”. “Updating the value of PC4” is performed using a route of “instruction decoder 6 → PC4” (not shown). Since these three types of paths are independent (not a common bus connection), simultaneous parallel processing is possible.
[0077]
The microprocessor 40 processes an interrupt. The instruction decoder 6 receives an interrupt input (not shown), and when the interrupt input signal becomes active, the instruction decoder 6 branches to an interrupt processing program prepared in advance. This is shown in FIG. FIG. 8 shows the operation of the microprocessor 40 in the form of a table similar to FIG. 7 for the interrupt processing program. In FIG. 8, the source number 71 is omitted.
[0078]
When an interrupt signal indicating that an exception factor has occurred during processing of the program 50 or the like, the three cycles 101 to 103 indicated by the cycle number 74 are executed in hardware. In the 101st cycle, the value of the address register 11 is copied (saved) to the save register 13, and at the same time, a predetermined value (fixed value) is substituted into the address register 11. Since the value of the address register 11 becomes a fixed value, the same stack area of the internal RAM 7 is always used when an interrupt occurs. Different areas can be used as a stack by appropriately changing the address register 11 in the interrupt processing program.
[0079]
In the 103rd cycle indicated by cycle number 74, the return address (PC4 value + 4) is stored at address 0 of the stack area indicated by the new value of address register 11, and at the same time, a fixed value is assigned to PC4. Since the value of PC4 becomes a fixed value, when an interrupt occurs, it always jumps to the same address (the first address of the interrupt processing program). Various processes can be performed by appropriately branching in the interrupt processing program.
[0080]
Also in this case, since the value of the address register 11 is changed in the 101st cycle, the upper address is delayed in the next 102th cycle. In the 102nd cycle, unlike the execution of the mnemonic code 72 ('NOP') inserted by the above-mentioned compiler, a wait cycle is executed by hardware control. In this waiting cycle, all internal buses and control signals are not changed and the current state is maintained, and the supply of the instruction code by the pipe 5 to the instruction decoder 6 is also stopped.
[0081]
In the 104th and subsequent cycles indicated by the cycle number 74, an interrupt process is performed, and at the end of the process, a mnemonic code 72 ("RETI") for returning from the interrupt process to the original process is always arranged. The In the 201st cycle in which this instruction “RETI” is executed, the contents of address 0 of the interrupt processing stack area are copied to PC4 to restore the value of PC4, and at the same time, the contents of save register 13 are copied to address register 11. Restore the original processing address before branching. As a result, the original process interrupted by the interrupt input can be resumed and executed from the content at the time of the interruption.
[0082]
The original process is restarted from the 203rd cycle indicated by the cycle number 74, but it is determined whether or not the instruction code (mnemonic code 72) executed first after restarting is an instruction referring to the internal RAM 7. Have difficulty. For this reason, since the contents of the address register 11 are changed in the 201st cycle, the 202th cycle is always executed before the 203th cycle, and the delay of the higher address is performed. Similarly to the 102nd cycle, this is a wait cycle by hardware control.
[0083]
When an instruction that refers to the internal RAM 7 is executed after the contents of the address register 11 are updated as described above, a wait cycle such as “NOP” is inserted, so the contents of the address register 11 are updated. Even so, a cycle for referring to the internal RAM 7 can be secured. For example, even the operation instruction in the third row in FIG. 5 can prepare the decode signal (GA000 to GA7FF) from the higher address when executed by the ALU 9. .
[0084]
Accordingly, the following operation is performed when such an arithmetic instruction is executed. That is, information is read from the internal RAM 7 based on the signal of the A bus address of the first port among the three independent ports corresponding to the three address decoding units 7A to 7C of the internal RAM 7. The second port The information is read from the internal RAM 7 based on the signal of the B bus address for the A, the read information is given to the ALU 9, and the calculation result is calculated based on the signal of the C bus address of the third port. Can be stored in one cycle.
[0085]
Further, as described above, the internal RAM 7 can be accessed at high speed based on the lower address from the instruction decoder 6 given to the A, B, and C bus addresses.
[0086]
(Embodiment 2)
In this embodiment, when a source program is input and an instruction code for accessing (referring to) the internal RAM 7 in the source program is detected, an instruction code ('NOP') for providing the above-described wait cycle is inserted. Thus, a compiler for compiling the source program is provided.
[0087]
FIG. 9 shows a microcomputer 80 that executes a compiling procedure according to the second embodiment. The microcomputer 80 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) 82 that stores data such as a compiler program (hereinafter simply referred to as a compiler), a RAM 83, an input / output I / F (Inter Face) 84, a keyboard. An input unit 85 for inputting information such as instructions from the outside, an output unit 86 for outputting information to the outside, a communication I / F 87 for connecting to various communication lines such as the Internet, and a recording medium 89 includes a recording medium driving unit 88 that is detachably inserted and accesses information to the inserted recording medium.
[0088]
The compiler may be supplied by being recorded in advance on the recording medium 89 and read by the recording medium driving unit 88, or may be supplied by being loaded from the network via the communication I / F 87.
[0089]
The input / output I / F 84 inputs / outputs various devices including the microprocessor 40. The compiler stored in the ROM 82 is executed under the control of the CPU 81, so that the high-level language source program prepared in the RAM 83 or the like is sequentially read and translated into machine language instructions for the microprocessor 40. The translated contents are stored in a predetermined area of the RAM 83. The machine language instruction sequence stored in a predetermined area of the RAM 83 is read out and applied to the microprocessor 40 as the data input 2 via the input / output I / F 84. The machine language instruction sequence read from the RAM 83 may be read via the communication I / F 87 and the network and may be given to the microprocessor 40 as the data input 2, or may be supplied to the recording medium 89 via the recording medium driving unit 88. And the contents of the recording medium 89 may be given to the microprocessor 40 as the data input 2.
[0090]
Here, it is assumed that the microprocessor 40 operates on the assumption that the microcomputer 80 is operating. Usually, however, the compiler stores a compilation result (instruction code string) in the recording medium 89, for example, After writing to the ROM connected to the address output 1 and the data input 2, the microprocessor 40 is operated.
[0091]
FIG. 10 is a flowchart showing a compile procedure according to the second embodiment, and the procedure shown in FIG. 10 is executed by executing the compiler in the ROM 82. A procedure for compiling the C language program 50 of FIG. 5 into the mnemonic code 72 of FIG. 7 will be described with reference to the flowchart of FIG. The compiler also assigns variables (including arguments) declared in the program 50 to the stack area as shown in FIG. 6, but the description thereof is omitted here. Further, the mnemonic code 72 sequentially generated following the procedure is sequentially stored in an internal memory (not shown) of the CPU 81. When there is no source code to be compiled (compilation of all source codes is completed), the sequence of mnemonic codes 72 in the internal memory is stored in a predetermined area of the RAM 83.
[0092]
First, the CPU 81 reads the program 50 file from the RAM 83 into an internal memory (not shown) (step S1). Next, it is determined whether or not there is a function code to be compiled in the read source file (step S2). If there is no code to be compiled, the sequence of mnemonic codes 72 (machine language instruction sequence) stored in the internal memory as a compilation result is output to a predetermined area of the RAM 83 (step S17). It is determined whether the content of the line is an instruction code that refers to the internal RAM 7 (step S3). If the instruction code refers to the internal RAM 7, the CPU 81 generates a mnemonic code 72 of “NOP” (step S4), and generates a mnemonic code 72 that refers to the internal RAM 7 based on the read contents (step S5). . Thereafter, the process proceeds to step S6.
[0093]
Since the instruction for calling the subroutine of the function func1 is described in a program included in another source code file (not shown), the mnemonic code “CALL func1” is not generated when the source code file is compiled (not shown). Not generated when compiling other source code files).
[0094]
The content read in the first line of the program 50 is the content defining the function func1 (YES in step S2). Since the first instruction of the program 50 is the instruction code on the third line and refers to the internal RAM 7 (YES in S3), the CPU 81 generates a mnemonic code 72 of “NOP” (step S4) and reads it. A mnemonic code 72 referring to the internal RAM 7 is generated based on the contents (step S5). Thereafter, the process proceeds to step S6.
[0095]
Since the instruction codes in the four lines are general instructions (NO in S6, NO in S11), the mnemonic code 72 is generated based on the read contents (step S16). Thereafter, the process proceeds to step S6.
[0096]
The CPU 81 reads the fifth line of the program 50. Since the read content is a subroutine call instruction code (YES in step S6), a corresponding mnemonic code 72 ('CALL func2') is generated (step S7). Since the source code on the sixth line, which is the first instruction returned from the subroutine of the function func2, is an instruction that refers to the internal RAM 7 (YES in step S8), a mnemonic code 72 of “NOP” is generated, and A mnemonic code 72 corresponding to an instruction referring to the internal RAM 7 is generated (steps S9 and S10). Then, it returns to step S6.
[0097]
Since the next 7th line is determined to be a subroutine end instruction (NO in step S6, YES in step S11), in order to return to the original subroutine, that is, to return to the subroutine that called the function func1, mnemonic code 72 ( 'DEC ADR') is generated (step S12), the mnemonic code 72 of 'NOP' is generated (step S13), the mnemonic code 72 of the return value copy instruction is generated (step S14), and the mnemonic code 72 ('RET) ') Is generated (step S15), and the process returns to step S2.
[0098]
This completes the compilation of the subroutine of the function func1, and the function func2 continues in the source file (YES in step S2). The first instruction of the subroutine of the function func2 is indicated by the instruction code on the 11th line. Since this is an instruction for referring to the internal RAM 7 (YES in step S3), the CPU 81 generates a mnemonic code 72 of “NOP” (step S4), and refers to the internal RAM 7 based on the read contents. The mnemonic code 72 is generated (step S5). Thereafter, the process proceeds to step S6.
[0099]
Since no code to be compiled remains at this time (YES in step S2), the machine language instruction sequence as a compilation result is output (stored) in a predetermined area of the RAM 83 (step S17). Thus, the compilation of the program 50 ends.
[0100]
(Modification of the embodiment)
In the first and second embodiments, since the delay amount from the upper address is large, when the reference of the internal RAM 7 is executed immediately after the value of the address register 11 is changed, the reference is completed in one cycle. Since the machine language instruction ('NOP') instructing that no operation is performed is inserted by the compiler, the amount of delay from the higher address is relatively small, so that the internal RAM 7 as described above is inserted. If the reference is completed in one cycle, the machine language instruction ('NOP') need not be inserted. Therefore, as an option of the compiler, whether to allow automatic insertion of machine language instructions ('NOP') may be variably set.
[0101]
In addition, a wait cycle by hardware control is inserted at the time of interrupt generation and return from interrupt processing. This can also be an option at the time of hardware design if the delay amount from the higher address is relatively small.
[0102]
In the first embodiment, the lower address is 5 bits and each local area of the internal RAM 7 is 32 words. However, the present invention is not limited to this. For example, in a microprocessor 40 in which a program that requires a large amount of local variables is executed, the system can be optimized, for example, by increasing the lower address to make each local area larger. Conversely, when the number of necessary local variables is small, it is possible to optimize the system by reducing the lower addresses and reducing the unused area of the internal RAM 7 to reduce the capacity and cost of the internal RAM 7. .
[0103]
(Effect of embodiment)
By using the microprocessor 40, an operation on a local variable that normally uses a stack can be performed in one cycle without a cycle for calculating an address. Further, since the stack is switched by changing the value of the address register 11, it is not necessary to save the value of the address register 11 used locally to the stack, and the overhead of calling a function (subroutine) is reduced. Further, the structure in which the output of the address register 11 and the output of the incrementer 12 are switched by the MUXs 15 and 16 makes it possible to pass arguments between areas before and after the function (subroutine) call. Further, when a function (subroutine) is called, the return address is saved, the address register 11 is carried up, and a value is assigned to the PC 4 can be executed in parallel, so that the function (subroutine) can be called at high speed.
[0104]
Therefore, the microprocessor 40 can execute a program of a language having a language specification that performs all operations on the stack, for example, a program written in Java (R) at high speed.
[0105]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0106]
【The invention's effect】
According to the microprocessor of the present invention, it is possible to speed up the access to the partial area referred to based on the lower address information of the internal memory. For example, a large amount of data can be accessed at a high speed as compared with the conventional method of calculating using a register file.
[0107]
According to the compiler of the present invention, since the instruction code for the waiting cycle is placed between the instruction code for changing the upper address information and the instruction code for referring to the internal memory, the internal memory is referred to. When executing the instruction code, the upper address information is updated and the time required to generate a signal for accessing the internal memory based on the updated upper address information is offset by the waiting time. In reference, an appropriate area can be referred to using the updated address information.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a microprocessor.
FIG. 2 is a diagram illustrating a configuration example of each cell of an SRAM.
FIG. 3 is a diagram illustrating an example of an array of SRAM cells.
FIG. 4 is a configuration diagram of an address decoding unit that generates a signal of each word line.
FIG. 5 is a diagram showing an example of a source program written in C language.
FIG. 6 is a diagram illustrating an example of data arrangement on an internal RAM when a program is executed.
FIG. 7 is a diagram showing the operation of the microprocessor for each cycle in a table format.
FIG. 8 is a diagram showing, in a tabular form, the operation of the microprocessor for each cycle when branching to an interrupt processing program.
FIG. 9 is a block diagram of a microcomputer that executes a compiling procedure;
FIG. 10 is a flowchart showing a compilation procedure.
[Explanation of symbols]
6 instruction decoder, 7 internal RAM, 7A, 7B, 7C address decoding unit, 9 ALU, 11 address register, 40 microprocessor, 41 upper address decoder, 42 lower address decoder.

Claims (17)

An internal memory for storing information accessed based on an address signal;
A calculation unit for performing various calculations including a calculation using information in the internal memory based on a command;
An instruction decoding unit that decodes a given instruction code and outputs control information for controlling each unit including the operation instruction based on the decoding result;
An address decoding unit that inputs and decodes given address information and outputs the address signal;
The address information includes upper address information and lower address information, and a delay from the input of the lower address information to the derivation of the address signal by the address decoding unit after the input of the upper address information A microprocessor characterized by being shorter than a delay until an address signal is derived. The address decoding unit decodes the higher-order address information in the address information and outputs a higher-order decode signal, and decodes the lower-order address information in the address information and outputs a lower-order decode signal. 2. The microprocessor according to claim 1, further comprising: a lower decoder; and a generation decoder that inputs the upper decoding signal and the lower decoding signal to generate and output the address signal. The address generation unit further includes an address generation unit that generates the upper address information.
An address register for storing the upper address information;
An address update unit that updates the upper address information stored in the address register based on the control information of the instruction decoding unit;
The microprocessor according to claim 1, wherein the lower address information is included in the control information output from the instruction decoding unit. A program counter for holding information for sequentially designating the instruction code to be given to the instruction decoding unit;
When the instruction code given to the instruction decoding unit is an instruction code instructing to branch to another processing routine,
According to the control information, the information held in the program counter is saved in the internal memory, the value of the program counter is changed to a specified value, and the contents of the address register are updated. The microprocessor according to any one of claims 1 to 3. The saving of the information held in the program counter to the internal memory, the change of the value of the program counter to a specified value, and the update of the contents of the address register are performed in parallel. Item 5. The microprocessor according to item 4. When an exception factor signal is input to the instruction decoding unit during processing,
In order to branch from the processing to the exception factor processing routine prepared in advance, the contents of the address register and the contents of the program counter are saved by the control information, and the contents of the address register are set to a predetermined fixed value. The microprocessor according to claim 4, wherein the microprocessor is changed to: When the instruction decoding unit is given an instruction code for returning from the branch destination processing routine to the original processing, the control information restores the contents of the program counter to the previously saved contents. The microprocessor according to any one of claims 4 to 6. When the instruction decoding unit is given an instruction code for returning from the branch destination processing routine to the original processing, the contents of the address register and the contents of the program counter are restored by the control information. The microprocessor according to any one of claims 4 to 6. The internal memory has three independent ports;
Read information from the internal memory based on the address signal for a first port of the three ports, and based on the address signal for a second port of the three ports Information is read from the internal memory, the read information is given to the calculation unit, and the calculation result is obtained based on the address signal for the third port of the three ports. The microprocessor according to any one of claims 1 to 8, wherein the operation of storing data in (1) is performed in one cycle. 10. The microprocessor according to claim 9, wherein the instruction code includes the lower address information of each of the address information for the three ports. The instruction code includes constant information;
11. The microprocessor according to claim 9, wherein the instruction decoding unit sends the constant information to a bus for supplying information read from the internal memory to the arithmetic unit. When branching to an exception handling routine according to the occurrence of an exception cause during processing, the contents of the address register are saved and updated to a fixed value, a cycle for waiting time is executed, and the value of the program counter is saved The microprocessor according to any one of claims 4 to 11, wherein the microprocessor is stored in the internal memory. 13. When returning from the exception handling routine to the original process before branching, the address register is restored to the saved contents, and a cycle for waiting time is executed. Microprocessor. A compiler that sequentially inputs source code constituting a source program, converts the source code into the instruction code for the microprocessor according to any one of claims 1 to 13, and outputs an instruction code string.
When the source code that refers to the internal memory is converted, if the instruction code that changes the upper address information has been converted immediately before, the instruction code of the source code in the instruction code string A compiler characterized by compiling to put an instruction code for a waiting cycle in front of each other. When the source code for instructing a subroutine call is detected in the source program, the information stored in the program counter is saved in the internal memory, and the value of the program counter is changed to a specified value. 15. The compiler according to claim 14, wherein the compiler converts the instruction code to instruct to update the contents of the address register. If the source code next to the source code instructing the subroutine call in the source program instructs to refer to the internal memory, the instruction code group instructing the return from the subroutine is sent to the instruction code group. The compiler according to claim 14, wherein the compiler is compiled so as to place an instruction code for a waiting cycle. An instruction code for the waiting cycle before the instruction code of the source code in the instruction code sequence when it is detected in the source program that the first source code of a subroutine indicates a reference to the internal memory The compiler according to any one of claims 14 to 16, wherein the compiler is compiled such that

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