[llvm-profdata] Support JSON as as an output-only format

This patch teaches llvm-profdata to output the sample profile in the
JSON format.  The new option is intended to be used for research and
development purposes.  For example, one can write a Python script to
take a JSON file and analyze how similar different inline instances of
a given function are to each other.

I've chosen JSON because Python can parse it reasonably fast, and it
just takes a couple of lines to read the whole data:

  import json
  with open ('profile.json') as f:
    profile = json.load(f)

Differential Revision: https://reviews.llvm.org/D130944

1 files changed, 20 insertions, 8 deletions

diff --git a/llvm/tools/llvm-profdata/llvm-profdata.cpp b/llvm/tools/llvm-profdata/llvm-profdata.cpp
index 3af8f80..e392128 100644
--- a/llvm/tools/llvm-profdata/llvm-profdata.cpp
+++ b/llvm/tools/llvm-profdata/llvm-profdata.cpp
@@ -2488,7 +2488,7 @@ static int showSampleProfile(const std::string &Filename, bool ShowCounts,
                              const std::string &ShowFunction,
                              bool ShowProfileSymbolList,
                              bool ShowSectionInfoOnly, bool ShowHotFuncList,
-                             raw_fd_ostream &OS) {
+                             bool JsonFormat, raw_fd_ostream &OS) {
   using namespace sampleprof;
   LLVMContext Context;
   auto ReaderOrErr =
@@ -2505,11 +2505,20 @@ static int showSampleProfile(const std::string &Filename, bool ShowCounts,
   if (std::error_code EC = Reader->read())
     exitWithErrorCode(EC, Filename);
 
-  if (ShowAllFunctions || ShowFunction.empty())
-    Reader->dump(OS);
-  else
+  if (ShowAllFunctions || ShowFunction.empty()) {
+    if (JsonFormat)
+      Reader->dumpJson(OS);
+    else
+      Reader->dump(OS);
+  } else {
+    if (JsonFormat)
+      exitWithError(
+          "the JSON format is supported only when all functions are to "
+          "be printed");
+
     // TODO: parse context string to support filtering by contexts.
     Reader->dumpFunctionProfile(StringRef(ShowFunction), OS);
+  }
 
   if (ShowProfileSymbolList) {
     std::unique_ptr<sampleprof::ProfileSymbolList> ReaderList =
@@ -2582,6 +2591,9 @@ static int show_main(int argc, const char *argv[]) {
   cl::opt<bool> TextFormat(
       "text", cl::init(false),
       cl::desc("Show instr profile data in text dump format"));
+  cl::opt<bool> JsonFormat(
+      "json", cl::init(false),
+      cl::desc("Show sample profile data in the JSON format"));
   cl::opt<bool> ShowIndirectCallTargets(
       "ic-targets", cl::init(false),
       cl::desc("Show indirect call site target values for shown functions"));
@@ -2679,10 +2691,10 @@ static int show_main(int argc, const char *argv[]) {
         ShowAllFunctions, ShowCS, ValueCutoff, OnlyListBelow, ShowFunction,
         TextFormat, ShowBinaryIds, ShowCovered, OS);
   if (ProfileKind == sample)
-    return showSampleProfile(Filename, ShowCounts, TopNFunctions,
-                             ShowAllFunctions, ShowDetailedSummary,
-                             ShowFunction, ShowProfileSymbolList,
-                             ShowSectionInfoOnly, ShowHotFuncList, OS);
+    return showSampleProfile(
+        Filename, ShowCounts, TopNFunctions, ShowAllFunctions,
+        ShowDetailedSummary, ShowFunction, ShowProfileSymbolList,
+        ShowSectionInfoOnly, ShowHotFuncList, JsonFormat, OS);
   return showMemProfProfile(Filename, ProfiledBinary, OS);
 }