Method and system for instruction-set architecture simulation using just in time compilation

• US 20030217248A1
• Filed: 12/03/2002
• Published: 11/20/2003
• Est. Priority Date: 03/27/2002
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Synopsys Incorporated
• Inventors: Myer, Heinrich, Leupers, Rainer, Hoffmann, Andreas, Braun, Gunnar, Nohl, Achim, Schliebusch, Oliver
• Granted Patent: US 8,086,438 B2
• Time in Patent Office: Days
• US Class Current: 712/208
• CPC Class Codes: G06F 30/33 Design verification, e.g. functional simulation or model checking
• CPC Class Codes: G06F 9/45504 Abstract machines for programme code execution, e.g. Java virtual machine [JVM], interpreters, emulators
• CPC Class Codes: G06F 9/45516 Runtime code conversion or optimisation

Abstract

A method of simulating a program. Compiled and interpretive techniques are combined into a just-in-time cached compiled technique. When an instruction of a program simulation is to be executed at run-time, a table of compiled instructions is accessed to determine whether compiled data for the instruction is stored in the table. If the compiled data is not therein, the instruction is compiled and stored in the table. The compiled data is returned to a simulator that is executing the program simulation. In another embodiment, before storing new information in the table, another table may be consulted to determine if the location to which the new information is to be stored is protected. If the table location is protected, the new information is not stored in the table. Rather, the new information is simply passed on to the simulator.

Claims

1. A method of simulating a program comprising:

a) determining if compiled data of an instruction of a program simulation is stored in a memory table of compiled instructions, in response to a request for said compiled data;

b) if said compiled data is not is said memory table, compiling said instruction and storing said compiled data in said memory table; and

c) returning said compiled data or said reference thereto to a simulator that is executing said program simulation.

2. A method according to claim 1, wherein said b) comprises identifying one or more operations to be used to simulate said instruction.

3. A method according to claim 2, wherein said b) further comprises decoding said instruction into one or more parameters.

4. A method according to claim 2, wherein said operations comprise LISA (Language for Instruction-Set Architectures) operations.

5. A method according to claim 2, further comprising:

d) invoking a function call to implement one of said operations.

6. A method according to claim 1, wherein said a) comprises matching a key in said memory table with a code for said instruction.

7. A method according to claim 6, wherein said a) comprises retrieving said code from an instruction register in said simulator.

8. A method according to claim 1, wherein said a) comprises receiving a request from said simulator for said compiled data or said reference thereto.

9. A method according to claim 1, wherein said b) further comprises decoding said instruction to identify a processor instruction and operands.

10. A method according to claim 1, wherein said instruction is a processor instruction in said simulation.

11. A method according to claim 1, wherein said program simulation is run-time dynamic.

12. A method according to claim 1, wherein said simulator is retargetable.

13. A method according to claim 1, wherein said compiled data is returned by returning a reference thereto.

14. A computer implemented method of simulating the execution of a set of instructions comprising:

a) accessing a first instruction to be simulated;

b) determining if compiled data relating to said first instruction is present in a memory stored table;

c) if said compiled data relating to said first instruction is present in said memory stored table, providing said compiled data to a simulator for execution thereof by a computer system; and

d) if said compiled data relating to said first instruction is not present in said memory stored table, compiling said first instruction to produce a compiled result and providing said compiled result to said simulator for execution thereof by a computer system.

15. A method as described in claim 14 further comprising:

e) storing said compiled result in said memory stored table and associating said compiled result with said first instruction.

16. A method as described in claim 15 further comprising repeating said a)-e) for a second instruction.

17. A method as described in claim 14 further comprising:

e) determining if a location in said memory stored table to which said compiled data is to be stored is protected; and

f) if said location is not protected, storing said compiled result in said memory stored table and associating said compiled result with said first instruction.

18. A computer implemented method of simulating the execution of a set of instructions comprising:

a) when an instruction of a program simulation is to be executed by a simulator at run-time, determining if information to simulate said instruction is stored in a memory table;

b) if said information is not therein, determining said information to be used to simulate said instruction;

c) determining if a location in said memory table to which said information is to be written is protected;

d) if said location is not protected, storing said information in said memory table location and returning said information to said simulator; and

e) if said location is protected, returning said information to said simulator without storing said information in said memory table.

19. A method according to claim 18, wherein said information comprises identifiers of operations for simulating said instruction.

20. A method according to claim 18, wherein said information comprises identifiers of LISA (Language for Instruction-Set Architectures) operations.

21. A method according to claim 18, wherein said information comprises identifiers of pre-compiled functions operable to implement LISA (Language for Instruction-Set Architectures) operations.

22. A method according to claim 18, wherein said instruction is a processor instruction in said simulation.

23. A method according to claim 18, wherein said program simulation is run-time dynamic.

24. A method according to claim 18, wherein said simulator is retargetable.

25. A method according to claim 18, wherein said d) comprises returning said information by returning a reference thereto.

26. A computer system for simulating a program, comprising:

a cache table for storing information for specifying operations to simulate an instruction-set architecture;

an instruction compiler for decoding instructions to be simulated, determining said information, and storing said information in said cache table; and

a program simulator for using said information to simulate said instruction-set architecture.

27. A computer system according to claim 26, further comprising a protection table for indicating whether locations in said cache table are protected from being overwritten.

28. A computer system according to claim 26, further comprising an interface for receiving a request for said information from said simulator and for returning said information to said simulator.

29. A computer system according to claim 26, wherein said simulator is for simulating the operation of a processor.

30. A computer system according to claim 26, wherein said simulator comprises a plurality of functions for simulating said instruction.

31. A computer system according to claim 30, wherein said plurality of functions comprise pre-compiled functions in the C programming language.

32. A computer system according to claim 26, wherein said information is based on LISA (Language for Instruction-Set Architectures) operations.

33. A computer system according to claim 26, wherein said cache table comprises references to C functions.

34. A computer system according to claim 26, wherein said cache table comprises an entry comprising a key and said information, wherein said key identifies a compiled instruction currently held at said entry.

35. A computer readable medium having stored therein instructions which when executed on a general purpose processor implement a method of simulating a processor, said method comprising:

a) determining if compiled data used in simulating an instruction is stored in a memory table of compiled instructions, in response to a request for said compiled data;

b) if said compiled data is not is said memory table;

b1) decoding said instruction;

b2) determining said compiled data;

b3) storing said compiled data in said memory table; and

c) returning said compiled data to a simulator for executing a program simulation.

36. A computer readable medium according to claim 35, wherein said b2) of said method comprises determining one or more LISA (Language for Instruction-Set Architectures) operations for simulating said instruction.

37. A computer readable medium according to claim 35, wherein said method further comprises:

d) invoking a function call to simulate said instruction.

38. A computer readable medium according to claim 35, wherein said program simulation is run-time dynamic.

39. A computer readable medium according to claim 35, wherein said simulator is retargetable.