Multiprocessor development environment
In a method of simulating a multi-processor system by running code that simulates the system on a host processor, a SPECULATE and a COMMIT instruction is used to mark an area of memory, shared across several simulated processors, and the code is translated at run time to a form required by the host processor. All instructions are mapped to a native instruction set of the host using two different code dictionaries: all instructions outside a SPECULATE/COMMIT region are mapped to the first of the two code dictionaries. If a SPECULATE instruction is encountered during runtime by a simulator running the code, the instructions are mapped to a native instruction set of the host using the second code dictionary.
1. A method of simulating a multi-processor system by running system code that simulates the system on a host processor, in which:
(a) a SPECULATE and a COMMIT instruction in the system code is used to mark an area of memory, shared across several simulated processors, and
(b) the system code is translated at run time to a form required by the host processor;
wherein:
(i) all instructions are mapped to a native instruction set of the host using two different code dictionaries, a first code dictionary and a second code dictionary; and
(ii) all instructions outside a SPECULATE/COMMIT region are mapped to a native instruction set of the host using the first code dictionary; and
(iii) instructions within a SPECULATE/COMMIT region are mapped to the native instruction set of the host using the second code dictionary which uses a model that more accurately represents a multi-level memory of a final hardware implementation of the multi-processor system.
2. The method of claim 1 wherein the multi-level memory allows the temporary storage of data associated with instructions within the SPECULATE/COMMIT region.
3. The method of claim 1 wherein the model simulates the way that hardware accesses shared memory only via a level 1 cache associated with the multi-processor system handling that instruction.
4. The method of claim 3 wherein simulating a failure of instructions within the SPECULATE/COMMIT region involves the simulator using knowledge of the associativity of the level 1 cache.
5. The method of claim 4 wherein simulating a failure of instructions within the SPECULATE/COMMIT region involves the steps of:
(a) the simulator suspending simulation of a first processor executing within the SPECULATE/COMMIT region in order to simulate another processor;
(b) the simulator traversing a data structure representing the level 1 cache to determine which lines of cache have had speculatively written data placed in them.
6. The method of claim 5 wherein addresses containing speculatively written data are then observed by placing a watchpoint on the corresponding addresses in shared memory.
7. The method of claim 6 wherein, if simulating a second processor leads to any of these watchpointed addresses being speculatively written to, the simulator will flag that speculation as failing for that second processor.
8. The method of claim 7 wherein resumption of simulation for the suspended first processor requires checking whether any of the watchpointed addresses associated with the suspended first processor have been modified by the second processor.
9. The method of claim 8 wherein, if a watchpointed address has been modified, then the simulator will direct the suspended processor to a simulated exception handler.