make llvm-profdata show -text work as advertised in the documentation

[rsmith]

Summary

Per LLVM's CommandGuide, llvm-profdata show -text is supposed to produce textual output that can be passed as input to further llvm-profdata invocations. This doesn't currently work for two reasons:

1. -text was not sufficient to enable the machine-readable text format output; instead, -text was effectively ignored if -counts was not also specified. (With this patch, -counts is instead ignored if -text is specified, because the machine-readable text format always includes counts.)
2. When the input data was an IR-level profile, the :ir marker was missing from the output, resulting in a text format output that would not be usable as profiling data due to function hash mismatches.

[davidxl]

lgtm

(-text option with show command is a 'mis-feature', -text should really be used together with the 'merge' command, but it is too late to remove it now).

llvm/trunk/test/tools/llvm-profdata/roundtrip.test

+RUN: llvm-profdata merge -o %t.0.profdata %S/Inputs/IR_profile.proftext
+RUN: llvm-profdata show -o %t.0.proftext -all-functions -text %t.0.profdata 
+RUN: diff %t.0.proftext %S/Inputs/IR_profile.proftext
+RUN: llvm-profdata merge -o %t.1.profdata %t.0.proftext
+RUN: llvm-profdata show -o %t.1.proftext -all-functions -text %t.1.profdata 
+RUN: diff %t.1.proftext %S/Inputs/IR_profile.proftext

llvm/trunk/tools/llvm-profdata/llvm-profdata.cpp

auto MinCmp = [](const std::pair<std::string, uint64_t> &v1,
     return v1.second > v2.second;
   };
 
   std::priority_queue<std::pair<std::string, uint64_t>,
                       std::vector<std::pair<std::string, uint64_t>>,
                       decltype(MinCmp)>
       HottestFuncs(MinCmp);
 
+  // Add marker so that IR-level instrumentation round-trips properly.
+  if (TextFormat && IsIRInstr)
+    OS << ":ir\n";
+
   for (const auto &Func : *Reader) {
     bool Show =
         ShowAllFunctions || (!ShowFunction.empty() &&
                              Func.Name.find(ShowFunction) != Func.Name.npos);
 
-    bool doTextFormatDump = (Show && ShowCounts && TextFormat);
+    bool doTextFormatDump = (Show && TextFormat);
 
     if (doTextFormatDump) {
       InstrProfSymtab &Symtab = Reader->getSymtab();
       InstrProfWriter::writeRecordInText(Func.Name, Func.Hash, Func, Symtab,
                                          OS);
       continue;
     }
 
if (Show) {
         traverseAllValueSites(Func, IPVK_MemOPSize, VPStats[IPVK_MemOPSize], OS,
                               nullptr);
       }
     }
   }
   if (Reader->hasError())
     exitWithError(Reader->getError(), Filename);
 
-  if (ShowCounts && TextFormat)
+  if (TextFormat)
     return 0;
   std::unique_ptr<ProfileSummary> PS(Builder.getSummary());
   OS << "Instrumentation level: "
      << (Reader->isIRLevelProfile() ? "IR" : "Front-end") << "\n";
   if (ShowAllFunctions || !ShowFunction.empty())
     OS << "Functions shown: " << ShownFunctions << "\n";
   OS << "Total functions: " << PS->getNumFunctions() << "\n";
   OS << "Maximum function count: " << PS->getMaxFunctionCount() << "\n";