How do you optimize a branch prediction?
One thing you can do in a high-level language is to eliminate branches by expressing the problem in terms of lookups or arithmetic. This helps branch prediction work better on the remaining branches, because there’s more “history” available. I’ve made huge performance improvements to bottleneck code with this approach.
What is branch prediction list different types of branch prediction?
Branch prediction schemes are of two types: static branch schemes and dynamic branch schemes. branch scheme (hardware techniques) is based on the hardware and it assembles the information during the run-time of the program.
How does branch prediction work?
Branch prediction attempts to guess whether a conditional jump will be taken or not. Branch target prediction attempts to guess the target of a taken conditional or unconditional jump before it is computed by decoding and executing the instruction itself.
In which stage branch prediction is done?
Working of Branch Prediction: BTB is a lookaside cache that sits to the side of Decode Instruction(DI) stage of 2 pipelines and monitors for branch instructions. The first time that a branch instruction enters the pipeline, the BTB uses its source memory to perform a lookup in the cache.
What is branch prediction and how can it control hazards?
the idea behind branch prediction is simple: if we can correctly predict whether branches are taken or not, we can reduce the stalls due to control hazards.
What is a branch prediction buffer?
Branch prediction buffers contain prediction about whether the next branch will be taken (T) or not (NT), but it does not supply the target PC value. A Branch Target Buffer (BTB) does this. Instr address Predicted PC. BTB is a cache that holds. (instr addr, predicted PC)
Why is branch prediction algorithm needed?
Conditional Branches present in the programs significantly affect the performance of the system. So we need to come up with efficient branch prediction mechanism so as to get the branch target address with high accuracy and thus minimizing the stalls associated with control hazards.
What is branch folding?
Branch folding is a technique where, on the prediction of most branches, the branch instruction is completely removed from the instruction stream presented to the execution pipeline. Branch folding can significantly improve the performance of branches, taking the CPI for branches significantly below 1.
What are the techniques to deal with control hazards?
Solutions for Control Hazards
- Pipeline stall cycles. Freeze the pipeline until the branch outcome and target are known, then proceed with fetch.
- Branch delay slots.
- Branch prediction.
- Indirect branch prediction.
- Return address stack (RAS).
What is the difference between MDR and Mar?
memory address register (MAR) – holds the address of the current instruction that is to be fetched from memory, or the address in memory to which data is to be transferred. memory data register (MDR) – holds the contents found at the address held in the MAR, or data which is to be transferred to primary memory.
What is delayed branching?
The delayed branch means that the instruction following the branch is always executed before the PC is modified to perform the branch.
What is the difference between static and dynamic branch prediction?
Static branch prediction makes fixed prediction of a branch to either taken or not taken; Dynamic branch prediction makes prediction based on previous history situation, by looking at history table.