Precise excecution of versioned store instructions

A method, comprising:

• executing versioned store instructions of a first thread within a first mode of operation, including:
• retiring a versioned store instruction only after a version comparison has been performed for the versioned store instruction;
• and
• suppressing retirement of instructions in the first thread that are younger than an oldest versioned store instruction of the first thread until the oldest versioned store instruction has retired.

An apparatus, comprising:

• a reorder buffer configured to maintain a program order of instructions and to retire instructions in program order;
• and
• a memory controller configured to compare version information for versioned store instructions with version information stored in cache or memory locations corresponding to the store instructions;
• wherein the apparatus is configured execute instructions of a first thread according to a first mode of operation in which the apparatus is configured to retire a versioned store instruction from the reorder buffer only after a version comparison for the versioned store instruction has been performed.