[LLVMbugs] [Bug 714] NEW: [loopopt] Need index set analysis/splitting

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Mon Mar 6 18:36:17 PST 2006


           Summary: [loopopt] Need index set analysis/splitting
           Product: libraries
           Version: 1.0
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Loop Optimizer
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sabre at nondot.org

Consider this:

#include <math.h>

void test(float *x, long ndat, float **y, float xcen,
                   long xmin, long xmax, float sigmal,
                   float contribution) {
        long i,k;
        float diff;

        for (i=xmin,k=0; i<=xmax; i++, k++) {
          if(i >= 0 && i < ndat) {
              diff = fabs(xcen - x[i])/sigmal;
              y[0][k] += contribution * 0.5*exp(-diff)/sigmal;


Through index set analysis, the two if statements inside the loop (comparing i to 0/ndat) can be 
hoisted out.


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