[ThinLTO] Add an option to llvm-lto to print some basic statistics for the index

[mehdi_amini]

clang-format

[tejohnson]

LGTM with change to refactor the new functionality into a separate function.

[mehdi_amini]

Can you confirm you mean a local (static) function? (And not a library function with a public API?)

[tejohnson]

In D24290#540314, @mehdi_amini wrote:

Can you confirm you mean a local (static) function? (And not a library function with a public API?)

Sorry, yes, the former. Just to keep it out of main().

[Prazek]

LGTM

test/ThinLTO/X86/funcimport.ll

 ; Do setup work for all below tests: generate bitcode and combined index
 ; RUN: opt -module-summary %s -o %t.bc
 ; RUN: opt -module-summary %p/Inputs/funcimport.ll -o %t2.bc
 ; RUN: llvm-lto -thinlto-action=thinlink -o %t3.bc %t.bc %t2.bc
 
+; RUN: llvm-lto -thinlto-index-stats %t3.bc | FileCheck %s -check-prefix=STATS
+; STATS: Index {{.*}} contains 24 nodes (13 functions, 3 alias, 8 globals) and 19 edges (8 refs and 11 calls)
+
 ; Ensure statics are promoted/renamed correctly from this file (all but
 ; constant variable need promotion).
 ; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=EXPORTSTATIC
 ; EXPORTSTATIC-DAG: @staticvar.llvm.0 = hidden global
 ; EXPORTSTATIC-DAG: @staticconstvar = internal unnamed_addr constant
 ; EXPORTSTATIC-DAG: @P.llvm.0 = hidden global void ()* null
 ; EXPORTSTATIC-DAG: define hidden i32 @staticfunc.llvm.0
 ; EXPORTSTATIC-DAG: define hidden void @staticfunc2.llvm.0

tools/llvm-lto/llvm-lto.cpp

 
 using namespace llvm;
 
 static cl::opt<char>
     OptLevel("O", cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
                            "(default = '-O2')"),
              cl::Prefix, cl::ZeroOrMore, cl::init('2'));
 
+static cl::opt<bool>
+    IndexStats("thinlto-index-stats",
+               cl::desc("Print statistic for the index in every input files"),
+               cl::init(false));
+
 static cl::opt<bool> DisableVerify(
     "disable-verify", cl::init(false),
     cl::desc("Do not run the verifier during the optimization pipeline"));
 
 static cl::opt<bool> DisableInline("disable-inlining", cl::init(false),
                                    cl::desc("Do not run the inliner pass"));
 
 static cl::opt<bool>
int main(int argc, char **argv) {
   // set up the TargetOptions for the machine
   TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
 
   if (ListSymbolsOnly) {
     listSymbols(Options);
     return 0;
   }
 
+  if (IndexStats) {
+    for (auto &Filename : InputFilenames) {
+      CurrentActivity = "loading file '" + Filename + "'";
+      ErrorOr<std::unique_ptr<ModuleSummaryIndex>> IndexOrErr =
+          llvm::getModuleSummaryIndexForFile(Filename, diagnosticHandler);
+      error(IndexOrErr, "error " + CurrentActivity);
+      std::unique_ptr<ModuleSummaryIndex> Index = std::move(IndexOrErr.get());
+      CurrentActivity = "";
+      // Skip files without a module summary.
+      if (!Index)
+        report_fatal_error(Filename + " does not contain an index");
+
+      unsigned Calls = 0, Refs = 0, Functions = 0, Alias = 0, Globals = 0;
+      for (auto &Summaries : *Index) {
+        for (auto &Summary : Summaries.second) {
+          Refs += Summary->refs().size();
+          if (auto *FuncSummary = dyn_cast<FunctionSummary>(Summary.get())) {
+            Functions++;
+            Calls += FuncSummary->calls().size();
+          } else if (isa<AliasSummary>(Summary.get()))
+            Alias++;
+          else
+            Globals++;
+        }
+      }
+      outs() << "Index " << Filename << " contains "
+             << (Alias + Globals + Functions) << " nodes (" << Functions
+             << " functions, " << Alias << " alias, " << Globals
+             << " globals) and " << (Calls + Refs) << " edges (" << Refs
+             << " refs and " << Calls << " calls)\n";
+    }
+    return 0;
+  }
+
   if (CheckHasObjC) {
     for (auto &Filename : InputFilenames) {
       ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
           MemoryBuffer::getFile(Filename);
       error(BufferOrErr, "error loading file '" + Filename + "'");
       auto Buffer = std::move(BufferOrErr.get());
       LLVMContext Ctx;
       if (llvm::isBitcodeContainingObjCCategory(*Buffer, Ctx))