[LLVMbugs] [Bug 2368] New: lcssa passes take 50% of the time in large testcase

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2368

           Summary: lcssa passes take 50% of the time in large testcase
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sharparrow1 at yahoo.com
                CC: resistor at mac.com, llvmbugs at cs.uiuc.edu


Original testcase at http://gcc.gnu.org/bugzilla/attachment.cgi?id=14134, from
gcc bug at http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33237.

Running opt -std-compile-opts over the attachment results in two lcssa passes
that take up half the time spent in opt.  (Report below.)

===-------------------------------------------------------------------------===
                      ... Pass execution timing report ...
===-------------------------------------------------------------------------===
  Total Execution Time: 50.9271 seconds (51.2564 wall clock)

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  ---
Name ---
  14.8209 ( 29.2%)   0.2360 ( 77.6%)  15.0569 ( 29.5%)  15.0543 ( 29.3%) 
Global Value Numbering
  12.6607 ( 25.0%)   0.0000 (  0.0%)  12.6607 ( 24.8%)  12.6599 ( 24.6%) 
Loop-Closed SSA Form Pass
  11.4527 ( 22.6%)   0.0000 (  0.0%)  11.4527 ( 22.4%)  11.4535 ( 22.3%) 
Loop-Closed SSA Form Pass
   1.5200 (  3.0%)   0.0000 (  0.0%)   1.5200 (  2.9%)   1.5184 (  2.9%) 
Simplify the CFG
   1.4920 (  2.9%)   0.0000 (  0.0%)   1.4920 (  2.9%)   1.4928 (  2.9%) 
Simplify the CFG
   1.2200 (  2.4%)   0.0000 (  0.0%)   1.2200 (  2.3%)   1.2207 (  2.3%)  Loop
Invariant Code Motion
   1.1120 (  2.1%)   0.0000 (  0.0%)   1.1120 (  2.1%)   1.1147 (  2.1%) 
Simplify the CFG
[snip]


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