Concurrent atomic execution
Executing a set one or more instructions atomically is disclosed. Executing includes saving a set of one or more register states in a software data structure, speculatively executing the set of instructions, and restoring the state of one or more registers when an abort indication is received.
1. A method for attempting to execute a set of one or more instructions speculatively, comprising:
executing a speculative execution command to directly cause the set of one or more instructions to be executed speculatively, wherein the speculative execution command does not read any value from any memory location and does not write any value to any memory location;
reading data from at least one memory location after executing the speculative execution command and before executing the set of instructions, wherein the read data can be used to determine whether a synchronization mechanism has been exclusively acquired;
speculatively executing the set of one or more instructions, the set of one or more instructions including at least one store to a memory location;
receiving a commit command that is an instruction indicating that the speculative execution is successful and at least one store is ready to be committed or an abort command that is an instruction indicating that an abort condition of the speculative execution command is detected;
in the event that the commit command is received, committing the store to the memory location; and
in the event that the abort command is received, reverting the store to the memory location.
2. A method as recited in claim 1 , further comprising using the read data to determine whether the synchronization mechanism has been exclusively acquired.
3. A method as recited in claim 2 , further comprising aborting the speculative execution before it is committed if it is determined that the synchronization mechanism has been exclusively acquired.
4. A method as recited in claim 1 , wherein the synchronization mechanism includes at least one of the following: a lock, a mutex, a semaphore, an object associated with a Java Virtual Machine monitor, an object associated with a Java synchronized method, an object associated with a Java synchronized block, an object associated with a .NET synchronized method, and an object associated with a .NET SyncBlock.
5. A system for attempting to execute a set of one or more instructions speculatively, comprising:
a processor configured to:
execute a speculative execution command in hardware, wherein the speculative execution command directly causes the set of one or more instructions to be executed speculatively, the speculative execution command does not read any value from any memory location and does not write any value to any memory location;
read data from at least one memory location after executing the speculative execution command and before executing the set of instructions, wherein the read data can be used to determine whether a synchronization mechanism has been exclusively acquired;
speculatively execute the set of one or more instructions, the set of one or more instructions including at least one store to a memory location;
receive a commit command that is an instruction indicating that the speculative execution is successful and at least one store is ready to be committed or an abort command that is an instruction indicating that an abort condition of the speculative execution command is detected;
in the event that the commit command is received, commit the store to the memory location; and
in the event that the abort command is received, revert the store to the memory location; and
a memory coupled with the processor, wherein the memory is configured to provide the processor with instructions.
6. A system as recited in claim 5 , wherein the process is further configured to use the read data to determine whether the synchronization mechanism has been exclusively acquired.
7. A system as recited in claim 6 , further comprising aborting the speculative execution before it is committed if it is determined that the synchronization mechanism has been exclusively acquired.
8. A computer program product for attempting to execute a set of one or more instructions speculatively, the computer program product being embodied in a computer readable storage medium and comprising computer instructions for:
executing a speculative execution command to directly cause the set of one or more instructions to be executed speculatively, wherein the speculative execution command does not read any value from any memory location and does not write any value to any memory location;
reading data from at least one memory location after executing the speculative execution command and before executing the set of instructions, wherein the read data can be used to determine whether a synchronization mechanism has been exclusively acquired;
speculatively executing the set of one or more instructions, the set of one or more instructions including at least one store to a memory location;
receiving a commit command that is an instruction indicating that the speculative execution is successful and the at least one store is ready to be committed or an abort command that is an instruction indicating that an abort condition of the speculative execution command is detected;
in the event that the commit command is received, committing the store to the memory location; and
in the event that the abort command is received, reverting the store to the memory location.
9. A computer program product as recited in claim 8 , further comprising using the read data to determine whether the synchronization mechanism has been exclusively acquired.
10. A method as recited in claim 9 , further comprising aborting the speculative execution before it is committed if it is determined that the synchronization mechanism has been exclusively acquired.