US 12,405,800 B2
Branch prediction based on a predicted confidence that a corresponding function of sampled register state correlates to a later branch instruction outcome
Houdhaifa Bouzguarrou, Austin, TX (US); and Rami Mohammad Al Sheikh, Morrisville, NC (US)
Assigned to Arm Limited, Cambridge (GB)
Filed by Arm Limited, Cambridge (GB)
Filed on Jan. 31, 2024, as Appl. No. 18/428,334.
Prior Publication US 2025/0245012 A1, Jul. 31, 2025
Int. Cl. G06F 9/38 (2018.01)
CPC G06F 9/3844 (2013.01) 20 Claims
OG exemplary drawing
 
1. An apparatus, comprising:
sampled state storage configured to store sampled register state of at least one register operand sampled at a sampling point in program flow;
a correlation prediction table to store at least one correlation prediction entry, each correlation prediction entry providing at least one confidence indication for a corresponding branch instruction;
wherein each confidence indication indicates a likelihood that a corresponding function of register state sampled at the sampling point correlates to a branch outcome for the corresponding branch instruction when said branch instruction is executed at a later point in program flow; and
prediction circuitry, wherein in response to a determination that a particular branch instruction later in program flow than the sampling point has a corresponding correlation prediction entry and that the corresponding correlation prediction entry provides a confidence indication meeting a prediction criterion, the prediction circuitry is configured to make a prediction of a branch outcome for the particular branch instruction based on performing a particular function of register state sampled at the sampling point, the particular function corresponding to the confidence indication meeting the prediction criterion.