[Profile] show distribution/histogram of indirect call profiles

[davidxl]

Summary

With collected value profile data, it is useful to see statistics such as how many value sites have <N> target values. This simple patch adds that support and dumps it as part of profile summary.

[vsk]

Seems straightforward. LGTM.

[davidxl]

For reference, xalanbmk IC histogram:

NumTargets, SiteCount
1, 1360
2, 73
3, 16
4, 4
5, 2
6, 3
7, 1
8, 9

dealII:

IC Value histogram :
NumTargets, SiteCount
1, 93
2, 13

povray:

IC Value histogram :
NumTargets, SiteCount
1, 30
2, 6
3, 2
4, 1
5, 2
6, 6
7, 1
8, 1

omnetpp:

IC Value histogram :
NumTargets, SiteCount
1, 181
2, 12
3, 4
4, 1
5, 0
6, 0
7, 3
8, 3

[Eugene.Zelenko]

Committed in r282017.

test/tools/llvm-profdata/value-prof.proftext

 #ICTEXT-NEXT: foo2:1000
 #ICTEXT-NEXT: 1
 #ICTEXT-NEXT: foo2:20000
 #
 
 #ICSUM: Total Number of Indirect Call Sites : 3
 #ICSUM: Total Number of Sites With Values : 2
 #ICSUM: Total Number of Profiled Values : 3
+#ICSUM: NumTargets, SiteCount
+#ICSUM  1, 1
+#ICSUM  2, 1
 

tools/llvm-profdata/llvm-profdata.cpp

     exitWithError(std::move(E), Filename);
 
   auto Reader = std::move(ReaderOrErr.get());
   bool IsIRInstr = Reader->isIRLevelProfile();
   size_t ShownFunctions = 0;
   uint64_t TotalNumValueSites = 0;
   uint64_t TotalNumValueSitesWithValueProfile = 0;
   uint64_t TotalNumValues = 0;
+  std::vector<unsigned> ICHistogram;
   for (const auto &Func : *Reader) {
     bool Show =
         ShowAllFunctions || (!ShowFunction.empty() &&
                              Func.Name.find(ShowFunction) != Func.Name.npos);
 
     bool doTextFormatDump = (Show && ShowCounts && TextFormat);
 
     if (doTextFormatDump) {

         uint32_t NS = Func.getNumValueSites(IPVK_IndirectCallTarget);
         OS << "    Indirect Target Results: \n";
         TotalNumValueSites += NS;
         for (size_t I = 0; I < NS; ++I) {
           uint32_t NV = Func.getNumValueDataForSite(IPVK_IndirectCallTarget, I);
           std::unique_ptr<InstrProfValueData[]> VD =
               Func.getValueForSite(IPVK_IndirectCallTarget, I);
           TotalNumValues += NV;
-          if (NV)
+          if (NV) {
             TotalNumValueSitesWithValueProfile++;
+            if (NV > ICHistogram.size())
+              ICHistogram.resize(NV, 0);
+            ICHistogram[NV - 1]++;
+          }
           for (uint32_t V = 0; V < NV; V++) {
             OS << "\t[ " << I << ", ";
             OS << Symtab.getFuncName(VD[V].Value) << ", " << VD[V].Count
                << " ]\n";
           }
         }
       }
     }

   OS << "Maximum function count: " << PS->getMaxFunctionCount() << "\n";
   OS << "Maximum internal block count: " << PS->getMaxInternalCount() << "\n";
   if (ShownFunctions && ShowIndirectCallTargets) {
     OS << "Total Number of Indirect Call Sites : " << TotalNumValueSites
        << "\n";
     OS << "Total Number of Sites With Values : "
        << TotalNumValueSitesWithValueProfile << "\n";
     OS << "Total Number of Profiled Values : " << TotalNumValues << "\n";
+
+    OS << "IC Value histogram : \n\tNumTargets, SiteCount\n";
+    for (unsigned I = 0; I < ICHistogram.size(); I++) {
+      OS << "\t" << I + 1 << ", " << ICHistogram[I] << "\n";
+    }
   }
 
   if (ShowDetailedSummary) {
     OS << "Detailed summary:\n";
     OS << "Total number of blocks: " << PS->getNumCounts() << "\n";
     OS << "Total count: " << PS->getTotalCount() << "\n";
     for (auto Entry : PS->getDetailedSummary()) {
       OS << Entry.NumCounts << " blocks with count >= " << Entry.MinCount