Advantages of Instruction-Level Parallelism
- Improved Performance: ILP can significantly improve the performance of processors by allowing multiple instructions to be executed simultaneously or out-of-order. This can lead to faster program execution and better system throughput.
- Efficient Resource Utilization: ILP can help to efficiently utilize processor resources by allowing multiple instructions to be executed at the same time. This can help to reduce resource wastage and increase efficiency.
- Reduced Instruction Dependency: ILP can help to reduce the number of instruction dependencies, which can limit the amount of instruction-level parallelism that can be exploited. This can help to improve performance and reduce bottlenecks.
- Increased Throughput: ILP can help to increase the overall throughput of processors by allowing multiple instructions to be executed simultaneously or out-of-order. This can help to improve the performance of multi-threaded applications and other parallel processing tasks.
Instruction Level Parallelism
Instruction Level Parallelism (ILP) is used to refer to the architecture in which multiple operations can be performed parallelly in a particular process, with its own set of resources – address space, registers, identifiers, state, and program counters. It refers to the compiler design techniques and processors designed to execute operations, like memory load and store, integer addition, and float multiplication, in parallel to improve the performance of the processors.
Examples of architectures that exploit ILP are VLIWs and superscalar Architecture. ILP processors have the same execution hardware as RISC processors. The machines without ILP have complex hardware which is hard to implement. A typical ILP allows multiple-cycle operations to be pipelined.
Example: Suppose, 4 operations can be carried out in a single clock cycle. So there will be 4 functional units, each attached to one of the operations, branch unit, and common register file in the ILP execution hardware. The sub-operations that can be performed by the functional units are Integer ALU, Integer Multiplication, Floating Point Operations, Load, and Store. Let the respective latencies be 1, 2, 3, 2, 1.
Let the sequence of instructions by
- y1 = x1*1010
- y2 = x2*1100
- z1 = y1+0010
- z2 = y2+0101
- t1 = t1+1
- p = q*1000
- clr = clr+0010
- r = r+0001