[llvm-profdata] Report if profile data file is IR- or FE-level

[davidxl]

lgtm

test/tools/llvm-profdata/show-instr-level.test

+RUN: llvm-profdata merge -o %t_clang.profdata %p/Inputs/clang_profile.proftext
+RUN: llvm-profdata show %t_clang.profdata | FileCheck %s -check-prefix=FE
+FE: Instrumentation level: Front-end
+
+RUN: llvm-profdata merge -o %t_ir.profdata %p/Inputs/IR_profile.proftext
+RUN: llvm-profdata show %t_ir.profdata | FileCheck %s -check-prefix=IR
+IR: Instrumentation level: IR

tools/llvm-profdata/llvm-profdata.cpp

for (const auto &Func : *Reader) {
     }
   }
   if (Reader->hasError())
     exitWithError(Reader->getError(), Filename);
 
   if (ShowCounts && 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";
   OS << "Maximum internal block count: " << PS->getMaxInternalCount() << "\n";
 
   if (TopN) {
     std::vector<std::pair<std::string, uint64_t>> SortedHottestFuncs;