Methods and apparatus for preserving precise exceptions in code reordering by using control speculation

摘要

Methods and apparatus for preserving precise exceptions in code reordering by using control speculation are disclosed. A disclosed system uses a control speculation module to reorder instructions within an application program and preserve precise exceptions. Instructions, excepting and non-excepting, can be reordered by the control speculation module if the instructions meet certain conditions. When an excepting instruction is reordered, a check instruction is inserted into the program execution path and a recovery block is generated. The check instruction determines if the reordered excepting instruction actually needs to generate an exception. The recovery block contains instructions to revert the effects of code reordering. If the check instruction detects the need for an exception, the recovery block is executed to restore the architectural state of the processor and the exception is handled.

主权项

1. A method of preserving exceptions in code reordering, the method comprising:
determining if a first instruction of a plurality of instructions is an excepting instruction; determining if the first instruction is to be moved across a check instruction to an execution location that is before the check instruction; determining, with a processor, a second instruction in the plurality of instructions that computes a previous value of a target register associated with the first instruction when (1) the first instruction is not an excepting instruction and (2) the first instruction is to be moved across a check instruction to an execution location that is before the check instruction; and inserting, with the processor, a third instruction into the plurality of instructions to save the previous value of the target register.