Method and system for deferring exceptions generated during speculative execution

A method for supporting speculative execution comprising:

• providing a predetermined number of speculative operations in an instruction set architecture of a central processing unit;
• specifying a mode of the central processing unit by setting a mode bit in a register of the central processing unit;
• reading the mode bit in the register to determine the mode of the central processing unit and if the mode bit indicates that the speculative operations are to be operated as non-speculative operations, then
• operating the speculative operations as non-speculative operations;
• otherwise, executing speculative operations and if an exception is generated from a speculative operation then
• deferring the exception by storing information that identifies that an exception has occurred,
• executing a non-speculative operation including a check operation to check for a deferred exception,
• checking for a deferred exception by reading a destination register of a speculative operation, and
• if an exception is detected in a non-speculative operations, then reporting the exception.

A system for supporting speculative execution comprising:

• a register file including a general purpose register;
• and
• a functional unit in communication with the register file for executing operations, the functional unit including circuitry for recognizing speculative and non-speculative operations, the functional unit in communication with the register file for storing information indicating that an exception has been deferred if a speculative operation generates the exception, and for checking for deferred exceptions;
• wherein the circuitry for recognizing speculative and non-speculative operations includes a register for storing a mode bit identifying a mode of the central processing unit and further includes circuitry for reading the mode bit to determine whether an operation is to be treated as a speculative or non-speculative operation.