[LLVMbugs] [Bug 415] NEW: [ipcp] Sparse conditional IP constant propagation

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Wed Aug 4 13:12:57 PDT 2004


           Summary: [ipcp] Sparse conditional IP constant propagation
           Product: libraries
           Version: 1.0
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Interprocedural Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sabre at nondot.org

Brian pointed out that the Olden/mst benchmark has code that basically looks
like this:

main() {
  Do_all_BlueRule(..., 1, 0);

void Do_all_BlueRule(..., int nproc, int pn) {
  if (nproc > 1) {
    Do_all_BlueRule(nproc/2, nproc/2+pn);


The observation is that Do_all_BlueRule contains a bunch of code that is
dynamically dead, but it requires a smarter IPCP algorithm to notice it (the
unreachable recursive call causes us to miss this).

It seems like an aggressive IPCP coupled with SCCP'y techniques could solve this
pretty easily.


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