Software hint to improve the branch target prediction accuracy
A field is defined in branch instructions which is interpreted by software as "Hint" bits and these bits are used to signal the processor of special circumstances that may arise when doing speculative branch instruction execution to enable better branch address prediction accuracy and a re...
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Zusammenfassung: | A field is defined in branch instructions which is interpreted by software as "Hint" bits and these bits are used to signal the processor of special circumstances that may arise when doing speculative branch instruction execution to enable better branch address prediction accuracy and a reduction in link stack corruption which improves overall execution times. A programmer or compiler determines if a branch instruction usage fits in the context for a Hint action. If so, the compiler or programmer, using assembly/machine language, sets Hint bits in the branch instruction when it is compiled. If the branch is later speculatively executed, the processor decodes the tint bits and executes and a hardware action corresponding the decode of the Hint bits. These Hints include four specific Hint actions, however, the field reserved for Hint bits is five bit wide reserving up to thirty-two specific Hint cases may be specified. These Hint cases (or flint bits) may be interpreted differently for each type of branch instruction supported. |
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