Register renaming - Revision history

Jnc: better cat

2018-12-15T14:05:02Z

better cat

Jnc: better cat

2018-12-14T21:57:33Z

better cat

Jnc: +cat

2018-12-13T03:12:57Z

+cat

Jnc: typos

2018-12-05T19:37:36Z

typos

Jnc: A pretty good start

2018-12-05T16:19:46Z

A pretty good start

New page

'''Register renaming''' is a technique used in the implementation of [[superscalar]] [[Central Processing Unit|processors]], particularly in those using [[out-of-order execution]], to avoid 'stalls' caused by conflicts over register usage.

When an [[instruction]] wants to store its result in a [[register]], the old contents of which some prior (in [[program]] terms, not [[execute|execution]] terms) needs to use as an input, the first instruction cannot complete until the second has started. If the first instruction instead places its output in another, 'hidden' internal register, the conflict can be avoided. Later references to the output of the first instruction will of course have to use the value in the hidden internal register - this is the renaming.

One cause of this is the fact that due to the fixed [[word]] size used for an [[instruction set]], not many bits are available to name registers, but modern processors can have a lot of registers, more than can be named in the instructions - use of these keeps the data in the CPU, where it is quickly accessible. Register renaming is however needed to make use of them.

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-'''Register renaming''' is a technique used in the implementation of [[superscalar]] [[Central Processing Unit|processors]], particularly in those using [[out-of-order execution]], to avoid 'stalls' caused by conflicts over register usage.
+'''Register renaming''' is a technique used in the implementation of [[superscalar]] [[Central Processing Unit|processors]], particularly in those using [[out-of-order execution]], to avoid 'stalls' caused by conflicts over [[register]] usage.
-When an [[instruction]] wants to store its result in a [[register]], the old contents of which some prior (in [[program]] terms, not [[execute|execution]] terms) needs to use as an input, the first instruction cannot complete until the second has started. If the first instruction instead places its output in another, 'hidden' internal register, the conflict can be avoided. Later references to the output of the first instruction will of course have to use the value in the hidden internal register - this is the renaming.
+When an [[instruction]] wants to store its result in a register, the old contents of which some prior instruction (in [[program]] terms, not [[execute|execution]] time terms) needs to use as an input, the first instruction cannot complete until the second has started. If the first instruction instead places its output in another, 'hidden' internal register, the conflict can be avoided. Later references to the output of the first instruction will of course have to use the value in the hidden internal register - this is the renaming.
 One cause of this is the fact that due to the fixed [[word]] size used for an [[instruction set]], not many bits are available to name registers, but modern processors can have a lot of registers, more than can be named in the instructions - use of these keeps the data in the CPU, where it is quickly accessible. Register renaming is however needed to make use of them.
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