Restoring a register renaming map

A register renaming and register technology, applied in instruments, machine execution devices, computing, etc., can solve problems such as sacrificing performance

Inactive Publication Date: 2013-07-10
MIPS TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this requires providing a large amount of storage in which to hold all the snapshots, because if all the snapshot storage is used, the instruction flow must be stalled until the snapshot can be saved again, sacrificing performance

Method used

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  • Restoring a register renaming map
  • Restoring a register renaming map
  • Restoring a register renaming map

Examples

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Embodiment Construction

[0021] The embodiments are described below by way of example only. These examples represent the best way currently known to the applicant to put the embodiments into practice, but they are not the only way this can be done. The instructions describe the function of the example and the sequence of steps for building and operating the example. However, the same or equivalent functions and sequences can be accomplished with different examples.

[0022] Described below are techniques for restoring a register renaming map to recover from unexpected changes in program flow in an out-of-order processor. Two techniques are described, which can be combined to further improve performance. Compared to the technique of saving a snapshot of the state of the register renaming map for every flow-risk instruction issued, the first technique reduces the amount of storage space used to implement recovery from unexpected flow changes. This technique reserves a predetermined amount of storage ...

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Abstract

A technique for restoring a register renaming map is described. In one example, a restore table having a number of storage locations saves a copy of the register renaming map whenever a flow-risk instruction is passed to a re-order buffer. When all storage locations are full, further instructions still pass to the re-order buffer, but a copy of the map is not saved. A storage location subsequently becomes available when its associated flow-risk instruction is executed. A register renaming map state for an unrecorded flow-risk instruction passed to the re-order buffer whilst the storage locations were full is generated and stored in the available location. This is generated using the restore table entry for a previous flow-risk instruction and re-order buffer values for intervening instructions between the previous and unrecorded flow-risk instructions. The restore table can be used to restore the map if an unexpected change in instruction flow occurs.

Description

Background technique [0001] Out-of-order microprocessors can provide improved computing performance by executing instructions in a sequence different from the order in the program, such that instructions are executed when their input data is available, rather than waiting for execution of previous instructions in the program. To allow instructions to run out of order on a microprocessor, it is useful to be able to rename registers used by instructions. This enables the removal of "write-after-read" (WAR) dependencies from directives, since these dependencies are not real dependencies. By using register renaming and removing these dependencies, more instructions can be executed out of program sequence and performance is further improved. Register renaming is performed by maintaining a map in which registers named in instructions (called architectural registers) are mapped onto the physical registers of the microprocessor. [0002] But the flow of instructions in a program som...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F9/38
CPCG06F9/384G06F9/3863G06F9/3858G06F9/3861G06F9/3836G06F9/3856G06F9/30043
Inventor H·杰克逊
Owner MIPS TECH INC
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