Computer Science – 16.2 Translation Software | e-Consult
16.2 Translation Software (1 questions)
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Loop unrolling is an optimization technique where the compiler replicates the body of a loop multiple times to reduce the overhead of loop control (incrementing the loop counter and checking the loop condition). This can improve performance by reducing the number of loop control instructions.
Example:
Original Loop (Pseudocode):
| Iteration 1: x = x + 1 |
| Iteration 2: x = x + 1 |
| Iteration 3: x = x + 1 |
| ... |
| Iteration n: x = x + 1 |
Unrolled Loop (Pseudocode - unrolled by a factor of 2):
| x = x + 1 |
| x = x + 1 |
| x = x + 1 |
| x = x + 1 |
| ... |
| x = x + 1 |
In the unrolled version, the loop body is executed twice for each iteration of the original loop. This reduces the number of times the loop condition needs to be checked and the loop counter updated.
Benefits of Loop Unrolling:
- Reduced Loop Control Overhead: Fewer loop control instructions lead to faster execution.
- Improved Instruction Cache Utilization: More instructions are fetched into the instruction cache, reducing cache misses.
Drawbacks of Loop Unrolling:
- Increased Code Size: The unrolled loop is larger than the original loop, which can increase code size and potentially memory usage.
- Code Complexity: Unrolling can make the code harder to read and maintain.