Loop If-Split
If-split is an optimization technique that restructures loop-nested if-else statements by transforming them into separate independent loops. This transformation simplifies control flow, making data dependency analysis more efficient and increasing the potential for parallel execution. By eliminating branching within a loop, if-split enhances performance, particularly in scenarios where different execution paths can be processed independently. This technique is especially useful in optimizing loops for better hardware utilization and improved computational efficiency.
Loop If-Split Transformation in emmtrix Studio
emmtrix Studio implements loop if-split using #pragma directives or via the GUI. If-split is a transformation that splits loop-nested if-else statements into independent loops. The transformation can be applied only on if-else statements with different paths.
Typical Usage and Benefits
If-split is used to simplify data dependency analysis by generating less complex control-flow graphs. If-split increases potential for parallel execution.
Example
/* The following code tests loop if-split transformation applied to a for loop: */
#include <stdio.h>
int main(void) {
#pragma EMX_TRANSFORMATION IfSplit
for (j = 0; j < 8; j++) {
if (j < 4) {
suma += a[j];
} else {
sumb += b[j];
}
}
return 0;
}
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/* The generated code includes two loops, one separate loop for each of the original loop body state-
ments: */
#include <stdio.h>
int main(void) {
for (j = 0; j < 4; j = j + 1) {
{
suma = suma + a[j];
}
}
for (j = 4; j < 8; j = j + 1) {
{
sumb = sumb + b[j];
}
}
return 0;
}
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