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The trade-off between fast branch prediction and good branch prediction is sometimes dealt with by having two branch predictors. The first branch predictor is fast and simple. The second branch predictor, which is slower, more complicated, and with bigger tables, will override a possibly wrong prediction made by the first predictor.
In computer architecture, predication is a feature that provides an alternative to conditional transfer of control, as implemented by conditional branch machine instructions. Predication works by having conditional ( predicated ) non-branch instructions associated with a predicate , a Boolean value used by the instruction to control whether the ...
An example of a simple hardware branch prediction scheme is to assume that all backward branches (i.e. to a smaller program counter) are taken (because they are part of a loop), and all forward branches (to a larger program counter) are not taken (because they leave a loop).
In computer architecture, a branch target predictor is the part of a processor that predicts the target, i.e., the address of the instruction that is executed next, of a taken conditional branch or unconditional branch instruction before the target of the branch instruction is computed by the execution unit of the processor.
Speculative execution is an optimization technique where a computer system performs some task that may not be needed. Work is done before it is known whether it is actually needed, so as to prevent a delay that would have to be incurred by doing the work after it is known that it is needed.
The local predictor is a two-level table which records the history of individual branches. It consists of a 1,024-entry by 10-bit branch history table. A two-level table was used as the prediction accuracy is similar to that of a larger single-level table while requiring fewer bits of storage. It has a 1,024-entry branch prediction table.
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Memory dependence prediction for loads and stores is analogous to branch prediction for conditional branch instructions. In branch prediction, the branch predictor predicts which way the branch will resolve before it is known. The processor can then speculatively fetch and execute instructions down one of the paths of the branch. Later, when ...