tools/llvm-remarkutil/RemarkSizeDiff.cpp - llvm-project/llvm - Git at Google

 //===-------------- RemarkSizeDiff.cpp ------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// Diffs instruction count and stack size remarks between two remark files.
 ///
 /// This is intended for use by compiler developers who want to see how their
 /// changes impact program code size.
 ///
 //===----------------------------------------------------------------------===//

 #include "RemarkUtilHelpers.h"
 #include "RemarkUtilRegistry.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/JSON.h"

 using namespace llvm;
 using namespace remarks;
 using namespace remarkutil;
 static cl::SubCommand
     RemarkSizeDiffUtil("size-diff",
                        "Diff instruction count and stack size remarks "
                        "between two remark files");
 enum ReportStyleOptions { human_output, json_output };
 static cl::opt<std::string> InputFileNameA(cl::Positional, cl::Required,
                                            cl::sub(RemarkSizeDiffUtil),
                                            cl::desc("remarks_a"));
 static cl::opt<std::string> InputFileNameB(cl::Positional, cl::Required,
                                            cl::sub(RemarkSizeDiffUtil),
                                            cl::desc("remarks_b"));
 static cl::opt<std::string> OutputFilename("o", cl::init("-"),
                                            cl::sub(RemarkSizeDiffUtil),
                                            cl::desc("Output"),
                                            cl::value_desc("file"));
 INPUT_FORMAT_COMMAND_LINE_OPTIONS(RemarkSizeDiffUtil)
 static cl::opt<ReportStyleOptions> ReportStyle(
     "report_style", cl::sub(RemarkSizeDiffUtil),
     cl::init(ReportStyleOptions::human_output),
     cl::desc("Choose the report output format:"),
     cl::values(clEnumValN(human_output, "human", "Human-readable format"),
                clEnumValN(json_output, "json", "JSON format")));
 static cl::opt<bool> PrettyPrint("pretty", cl::sub(RemarkSizeDiffUtil),
                                  cl::init(false),
                                  cl::desc("Pretty-print JSON"));

 /// Contains information from size remarks.
 // This is a little nicer to read than a std::pair.
 struct InstCountAndStackSize {
   int64_t InstCount = 0;
   int64_t StackSize = 0;
 };

 /// Represents which files a function appeared in.
 enum FilesPresent { A, B, BOTH };

 /// Contains the data from the remarks in file A and file B for some function.
 /// E.g. instruction count, stack size...
 struct FunctionDiff {
   /// Function name from the remark.
   std::string FuncName;
   // Idx 0 = A, Idx 1 = B.
   int64_t InstCount[2] = {0, 0};
   int64_t StackSize[2] = {0, 0};

   // Calculate diffs between the first and second files.
   int64_t getInstDiff() const { return InstCount[1] - InstCount[0]; }
   int64_t getStackDiff() const { return StackSize[1] - StackSize[0]; }

   // Accessors for the remarks from the first file.
   int64_t getInstCountA() const { return InstCount[0]; }
   int64_t getStackSizeA() const { return StackSize[0]; }

   // Accessors for the remarks from the second file.
   int64_t getInstCountB() const { return InstCount[1]; }
   int64_t getStackSizeB() const { return StackSize[1]; }

   /// \returns which files this function was present in.
   FilesPresent getFilesPresent() const {
     if (getInstCountA() == 0)
       return B;
     if (getInstCountB() == 0)
       return A;
     return BOTH;
   }

   FunctionDiff(StringRef FuncName, const InstCountAndStackSize &A,
                const InstCountAndStackSize &B)
       : FuncName(FuncName) {
     InstCount[0] = A.InstCount;
     InstCount[1] = B.InstCount;
     StackSize[0] = A.StackSize;
     StackSize[1] = B.StackSize;
   }
 };

 /// Organizes the diffs into 3 categories:
 /// - Functions which only appeared in the first file
 /// - Functions which only appeared in the second file
 /// - Functions which appeared in both files
 struct DiffsCategorizedByFilesPresent {
   /// Diffs for functions which only appeared in the first file.
   SmallVector<FunctionDiff> OnlyInA;

   /// Diffs for functions which only appeared in the second file.
   SmallVector<FunctionDiff> OnlyInB;

   /// Diffs for functions which appeared in both files.
   SmallVector<FunctionDiff> InBoth;

   /// Add a diff to the appropriate list.
   void addDiff(FunctionDiff &FD) {
     switch (FD.getFilesPresent()) {
     case A:
       OnlyInA.push_back(FD);
       break;
     case B:
       OnlyInB.push_back(FD);
       break;
     case BOTH:
       InBoth.push_back(FD);
       break;
     }
   }
 };

 static void printFunctionDiff(const FunctionDiff &FD, llvm::raw_ostream &OS) {
   // Describe which files the function had remarks in.
   FilesPresent FP = FD.getFilesPresent();
   const std::string &FuncName = FD.FuncName;
   const int64_t InstDiff = FD.getInstDiff();
   assert(InstDiff && "Shouldn't get functions with no size change?");
   const int64_t StackDiff = FD.getStackDiff();
   // Output an indicator denoting which files the function was present in.
   switch (FP) {
   case FilesPresent::A:
     OS << "-- ";
     break;
   case FilesPresent::B:
     OS << "++ ";
     break;
   case FilesPresent::BOTH:
     OS << "== ";
     break;
   }
   // Output an indicator denoting if a function changed in size.
   if (InstDiff > 0)
     OS << "> ";
   else
     OS << "< ";
   OS << FuncName << ", ";
   OS << InstDiff << " instrs, ";
   OS << StackDiff << " stack B";
   OS << "\n";
 }

 /// Print an item in the summary section.
 ///
 /// \p TotalA - Total count of the metric in file A.
 /// \p TotalB - Total count of the metric in file B.
 /// \p Metric - Name of the metric we want to print (e.g. instruction
 /// count).
 /// \p OS - The output stream.
 static void printSummaryItem(int64_t TotalA, int64_t TotalB, StringRef Metric,
                              llvm::raw_ostream &OS) {
   OS << "  " << Metric << ": ";
   int64_t TotalDiff = TotalB - TotalA;
   if (TotalDiff == 0) {
     OS << "None\n";
     return;
   }
   OS << TotalDiff << " (" << formatv("{0:p}", TotalDiff / (double)TotalA)
      << ")\n";
 }

 /// Print all contents of \p Diff and a high-level summary of the differences.
 static void printDiffsCategorizedByFilesPresent(
     DiffsCategorizedByFilesPresent &DiffsByFilesPresent,
     llvm::raw_ostream &OS) {
   int64_t InstrsA = 0;
   int64_t InstrsB = 0;
   int64_t StackA = 0;
   int64_t StackB = 0;
   // Helper lambda to sort + print a list of diffs.
   auto PrintDiffList = [&](SmallVector<FunctionDiff> &FunctionDiffList) {
     if (FunctionDiffList.empty())
       return;
     stable_sort(FunctionDiffList,
                 [](const FunctionDiff &LHS, const FunctionDiff &RHS) {
                   return LHS.getInstDiff() < RHS.getInstDiff();
                 });
     for (const auto &FuncDiff : FunctionDiffList) {
       // If there is a difference in instruction count, then print out info for
       // the function.
       if (FuncDiff.getInstDiff())
         printFunctionDiff(FuncDiff, OS);
       InstrsA += FuncDiff.getInstCountA();
       InstrsB += FuncDiff.getInstCountB();
       StackA += FuncDiff.getStackSizeA();
       StackB += FuncDiff.getStackSizeB();
     }
   };
   PrintDiffList(DiffsByFilesPresent.OnlyInA);
   PrintDiffList(DiffsByFilesPresent.OnlyInB);
   PrintDiffList(DiffsByFilesPresent.InBoth);
   OS << "\n### Summary ###\n";
   OS << "Total change: \n";
   printSummaryItem(InstrsA, InstrsB, "instruction count", OS);
   printSummaryItem(StackA, StackB, "stack byte usage", OS);
 }

 /// Collects an expected integer value from a given argument index in a remark.
 ///
 /// \p Remark - The remark.
 /// \p ArgIdx - The index where the integer value should be found.
 /// \p ExpectedKeyName - The expected key name for the index
 /// (e.g. "InstructionCount")
 ///
 /// \returns the integer value at the index if it exists, and the key-value pair
 /// is what is expected. Otherwise, returns an Error.
 static Expected<int64_t> getIntValFromKey(const remarks::Remark &Remark,
                                           unsigned ArgIdx,
                                           StringRef ExpectedKeyName) {
   auto KeyName = Remark.Args[ArgIdx].Key;
   if (KeyName != ExpectedKeyName)
     return createStringError(
         inconvertibleErrorCode(),
         Twine("Unexpected key at argument index " + std::to_string(ArgIdx) +
               ": Expected '" + ExpectedKeyName + "', got '" + KeyName + "'"));
   long long Val;
   auto ValStr = Remark.Args[ArgIdx].Val;
   if (getAsSignedInteger(ValStr, 0, Val))
     return createStringError(
         inconvertibleErrorCode(),
         Twine("Could not convert string to signed integer: " + ValStr));
   return static_cast<int64_t>(Val);
 }

 /// Collects relevant size information from \p Remark if it is an size-related
 /// remark of some kind (e.g. instruction count). Otherwise records nothing.
 ///
 /// \p Remark - The remark.
 /// \p FuncNameToSizeInfo - Maps function names to relevant size info.
 /// \p NumInstCountRemarksParsed - Keeps track of the number of instruction
 /// count remarks parsed. We need at least 1 in both files to produce a diff.
 static Error processRemark(const remarks::Remark &Remark,
                            StringMap<InstCountAndStackSize> &FuncNameToSizeInfo,
                            unsigned &NumInstCountRemarksParsed) {
   const auto &RemarkName = Remark.RemarkName;
   const auto &PassName = Remark.PassName;
   // Collect remarks which contain the number of instructions in a function.
   if (PassName == "asm-printer" && RemarkName == "InstructionCount") {
     // Expecting the 0-th argument to have the key "NumInstructions" and an
     // integer value.
     auto MaybeInstCount =
         getIntValFromKey(Remark, /*ArgIdx = */ 0, "NumInstructions");
     if (!MaybeInstCount)
       return MaybeInstCount.takeError();
     FuncNameToSizeInfo[Remark.FunctionName].InstCount = *MaybeInstCount;
     ++NumInstCountRemarksParsed;
   }
   // Collect remarks which contain the stack size of a function.
   else if (PassName == "prologepilog" && RemarkName == "StackSize") {
     // Expecting the 0-th argument to have the key "NumStackBytes" and an
     // integer value.
     auto MaybeStackSize =
         getIntValFromKey(Remark, /*ArgIdx = */ 0, "NumStackBytes");
     if (!MaybeStackSize)
       return MaybeStackSize.takeError();
     FuncNameToSizeInfo[Remark.FunctionName].StackSize = *MaybeStackSize;
   }
   // Either we collected a remark, or it's something we don't care about. In
   // both cases, this is a success.
   return Error::success();
 }

 /// Process all of the size-related remarks in a file.
 ///
 /// \param[in] InputFileName - Name of file to read from.
 /// \param[in, out] FuncNameToSizeInfo - Maps function names to relevant
 /// size info.
 static Error readFileAndProcessRemarks(
     StringRef InputFileName,
     StringMap<InstCountAndStackSize> &FuncNameToSizeInfo) {

   auto MaybeBuf = getInputMemoryBuffer(InputFileName);
   if (!MaybeBuf)
     return MaybeBuf.takeError();
   auto MaybeParser =
       createRemarkParserFromMeta(InputFormat, (*MaybeBuf)->getBuffer());
   if (!MaybeParser)
     return MaybeParser.takeError();
   auto &Parser = **MaybeParser;
   auto MaybeRemark = Parser.next();
   unsigned NumInstCountRemarksParsed = 0;
   for (; MaybeRemark; MaybeRemark = Parser.next()) {
     if (auto E = processRemark(**MaybeRemark, FuncNameToSizeInfo,
                                NumInstCountRemarksParsed))
       return E;
   }
   auto E = MaybeRemark.takeError();
   if (!E.isA<remarks::EndOfFileError>())
     return E;
   consumeError(std::move(E));
   // We need at least one instruction count remark in each file to produce a
   // meaningful diff.
   if (NumInstCountRemarksParsed == 0)
     return createStringError(
         inconvertibleErrorCode(),
         "File '" + InputFileName +
             "' did not contain any instruction-count remarks!");
   return Error::success();
 }

 /// Wrapper function for readFileAndProcessRemarks which handles errors.
 ///
 /// \param[in] InputFileName - Name of file to read from.
 /// \param[out] FuncNameToSizeInfo - Populated with information from size
 /// remarks in the input file.
 ///
 /// \returns true if readFileAndProcessRemarks returned no errors. False
 /// otherwise.
 static Error tryReadFileAndProcessRemarks(
     StringRef InputFileName,
     StringMap<InstCountAndStackSize> &FuncNameToSizeInfo) {
   if (Error E = readFileAndProcessRemarks(InputFileName, FuncNameToSizeInfo)) {
     return E;
   }
   return Error::success();
 }

 /// Populates \p FuncDiffs with the difference between \p
 /// FuncNameToSizeInfoA and \p FuncNameToSizeInfoB.
 ///
 /// \param[in] FuncNameToSizeInfoA - Size info collected from the first
 /// remarks file.
 /// \param[in] FuncNameToSizeInfoB - Size info collected from
 /// the second remarks file.
 /// \param[out] DiffsByFilesPresent - Filled with the diff between \p
 /// FuncNameToSizeInfoA and \p FuncNameToSizeInfoB.
 static void
 computeDiff(const StringMap<InstCountAndStackSize> &FuncNameToSizeInfoA,
             const StringMap<InstCountAndStackSize> &FuncNameToSizeInfoB,
             DiffsCategorizedByFilesPresent &DiffsByFilesPresent) {
   SmallSet<std::string, 10> FuncNames;
   for (const auto &FuncName : FuncNameToSizeInfoA.keys())
     FuncNames.insert(FuncName.str());
   for (const auto &FuncName : FuncNameToSizeInfoB.keys())
     FuncNames.insert(FuncName.str());
   for (const std::string &FuncName : FuncNames) {
     const auto &SizeInfoA = FuncNameToSizeInfoA.lookup(FuncName);
     const auto &SizeInfoB = FuncNameToSizeInfoB.lookup(FuncName);
     FunctionDiff FuncDiff(FuncName, SizeInfoA, SizeInfoB);
     DiffsByFilesPresent.addDiff(FuncDiff);
   }
 }

 /// Attempt to get the output stream for writing the diff.
 static ErrorOr<std::unique_ptr<ToolOutputFile>> getOutputStream() {
   if (OutputFilename == "")
     OutputFilename = "-";
   std::error_code EC;
   auto Out = std::make_unique<ToolOutputFile>(OutputFilename, EC,
                                               sys::fs::OF_TextWithCRLF);
   if (!EC)
     return std::move(Out);
   return EC;
 }

 /// \return a json::Array representing all FunctionDiffs in \p FunctionDiffs.
 /// \p WhichFiles represents which files the functions in \p FunctionDiffs
 /// appeared in (A, B, or both).
 json::Array
 getFunctionDiffListAsJSON(const SmallVector<FunctionDiff> &FunctionDiffs,
                           const FilesPresent &WhichFiles) {
   json::Array FunctionDiffsAsJSON;
   int64_t InstCountA, InstCountB, StackSizeA, StackSizeB;
   for (auto &Diff : FunctionDiffs) {
     InstCountA = InstCountB = StackSizeA = StackSizeB = 0;
     switch (WhichFiles) {
     case BOTH:
       [[fallthrough]];
     case A:
       InstCountA = Diff.getInstCountA();
       StackSizeA = Diff.getStackSizeA();
       if (WhichFiles != BOTH)
         break;
       [[fallthrough]];
     case B:
       InstCountB = Diff.getInstCountB();
       StackSizeB = Diff.getStackSizeB();
       break;
     }
     // Each metric we care about is represented like:
     //   "Val": [A, B]
     // This allows any consumer of the JSON to calculate the diff using B - A.
     // This is somewhat wasteful for OnlyInA and OnlyInB (we only need A or B).
     // However, this should make writing consuming tools easier, since the tool
     // writer doesn't need to think about slightly different formats in each
     // section.
     json::Object FunctionObject({{"FunctionName", Diff.FuncName},
                                  {"InstCount", {InstCountA, InstCountB}},
                                  {"StackSize", {StackSizeA, StackSizeB}}});
     FunctionDiffsAsJSON.push_back(std::move(FunctionObject));
   }
   return FunctionDiffsAsJSON;
 }

 /// Output all diffs in \p DiffsByFilesPresent as a JSON report. This is
 /// intended for consumption by external tools.
 ///
 /// \p InputFileNameA - File A used to produce the report.
 /// \p InputFileNameB - File B used ot produce the report.
 /// \p OS - Output stream.
 ///
 /// JSON output includes:
 ///  - \p InputFileNameA and \p InputFileNameB under "Files".
 ///  - Functions present in both files under "InBoth".
 ///  - Functions present only in A in "OnlyInA".
 ///  - Functions present only in B in "OnlyInB".
 ///  - Instruction count and stack size differences for each function.
 ///
 /// Differences are represented using [count_a, count_b]. The actual difference
 /// can be computed via count_b - count_a.
 static void
 outputJSONForAllDiffs(StringRef InputFileNameA, StringRef InputFileNameB,
                       const DiffsCategorizedByFilesPresent &DiffsByFilesPresent,
                       llvm::raw_ostream &OS) {
   json::Object Output;
   // Include file names in the report.
   json::Object Files(
       {{"A", InputFileNameA.str()}, {"B", InputFileNameB.str()}});
   Output["Files"] = std::move(Files);
   Output["OnlyInA"] = getFunctionDiffListAsJSON(DiffsByFilesPresent.OnlyInA, A);
   Output["OnlyInB"] = getFunctionDiffListAsJSON(DiffsByFilesPresent.OnlyInB, B);
   Output["InBoth"] =
       getFunctionDiffListAsJSON(DiffsByFilesPresent.InBoth, BOTH);
   json::OStream JOS(OS, PrettyPrint ? 2 : 0);
   JOS.value(std::move(Output));
   OS << '\n';
 }

 /// Output all diffs in \p DiffsByFilesPresent using the desired output style.
 /// \returns Error::success() on success, and an Error otherwise.
 /// \p InputFileNameA - Name of input file A; may be used in the report.
 /// \p InputFileNameB - Name of input file B; may be used in the report.
 static Error
 outputAllDiffs(StringRef InputFileNameA, StringRef InputFileNameB,
                DiffsCategorizedByFilesPresent &DiffsByFilesPresent) {
   auto MaybeOF = getOutputStream();
   if (std::error_code EC = MaybeOF.getError())
     return errorCodeToError(EC);
   std::unique_ptr<ToolOutputFile> OF = std::move(*MaybeOF);
   switch (ReportStyle) {
   case human_output:
     printDiffsCategorizedByFilesPresent(DiffsByFilesPresent, OF->os());
     break;
   case json_output:
     outputJSONForAllDiffs(InputFileNameA, InputFileNameB, DiffsByFilesPresent,
                           OF->os());
     break;
   }
   OF->keep();
   return Error::success();
 }

 /// Boolean wrapper for outputDiff which handles errors.
 static Error
 tryOutputAllDiffs(StringRef InputFileNameA, StringRef InputFileNameB,
                   DiffsCategorizedByFilesPresent &DiffsByFilesPresent) {
   if (Error E =
           outputAllDiffs(InputFileNameA, InputFileNameB, DiffsByFilesPresent)) {
     return E;
   }
   return Error::success();
 }

 static Error trySizeSiff() {
   StringMap<InstCountAndStackSize> FuncNameToSizeInfoA;
   StringMap<InstCountAndStackSize> FuncNameToSizeInfoB;
   if (auto E =
           tryReadFileAndProcessRemarks(InputFileNameA, FuncNameToSizeInfoA))
     return E;
   if (auto E =
           tryReadFileAndProcessRemarks(InputFileNameB, FuncNameToSizeInfoB))
     return E;
   DiffsCategorizedByFilesPresent DiffsByFilesPresent;
   computeDiff(FuncNameToSizeInfoA, FuncNameToSizeInfoB, DiffsByFilesPresent);
   if (auto E = tryOutputAllDiffs(InputFileNameA, InputFileNameB,
                                  DiffsByFilesPresent))
     return E;
   return Error::success();
 }

 static CommandRegistration RemarkSizeSiffRegister(&RemarkSizeDiffUtil,
                                                   trySizeSiff);
	//===-------------- RemarkSizeDiff.cpp ------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	///
	/// \file
	/// Diffs instruction count and stack size remarks between two remark files.
	///
	/// This is intended for use by compiler developers who want to see how their
	/// changes impact program code size.
	///
	//===----------------------------------------------------------------------===//

	#include "RemarkUtilHelpers.h"
	#include "RemarkUtilRegistry.h"
	#include "llvm/ADT/SmallSet.h"
	#include "llvm/Support/FormatVariadic.h"
	#include "llvm/Support/JSON.h"

	using namespace llvm;
	using namespace remarks;
	using namespace remarkutil;
	static cl::SubCommand
	RemarkSizeDiffUtil("size-diff",
	"Diff instruction count and stack size remarks "
	"between two remark files");
	enum ReportStyleOptions { human_output, json_output };
	static cl::opt<std::string> InputFileNameA(cl::Positional, cl::Required,
	cl::sub(RemarkSizeDiffUtil),
	cl::desc("remarks_a"));
	static cl::opt<std::string> InputFileNameB(cl::Positional, cl::Required,
	cl::sub(RemarkSizeDiffUtil),
	cl::desc("remarks_b"));
	static cl::opt<std::string> OutputFilename("o", cl::init("-"),
	cl::sub(RemarkSizeDiffUtil),
	cl::desc("Output"),
	cl::value_desc("file"));
	INPUT_FORMAT_COMMAND_LINE_OPTIONS(RemarkSizeDiffUtil)
	static cl::opt<ReportStyleOptions> ReportStyle(
	"report_style", cl::sub(RemarkSizeDiffUtil),
	cl::init(ReportStyleOptions::human_output),
	cl::desc("Choose the report output format:"),
	cl::values(clEnumValN(human_output, "human", "Human-readable format"),
	clEnumValN(json_output, "json", "JSON format")));
	static cl::opt<bool> PrettyPrint("pretty", cl::sub(RemarkSizeDiffUtil),
	cl::init(false),
	cl::desc("Pretty-print JSON"));

	/// Contains information from size remarks.
	// This is a little nicer to read than a std::pair.
	struct InstCountAndStackSize {
	int64_t InstCount = 0;
	int64_t StackSize = 0;
	};

	/// Represents which files a function appeared in.
	enum FilesPresent { A, B, BOTH };

	/// Contains the data from the remarks in file A and file B for some function.
	/// E.g. instruction count, stack size...
	struct FunctionDiff {
	/// Function name from the remark.
	std::string FuncName;
	// Idx 0 = A, Idx 1 = B.
	int64_t InstCount[2] = {0, 0};
	int64_t StackSize[2] = {0, 0};

	// Calculate diffs between the first and second files.
	int64_t getInstDiff() const { return InstCount[1] - InstCount[0]; }
	int64_t getStackDiff() const { return StackSize[1] - StackSize[0]; }

	// Accessors for the remarks from the first file.
	int64_t getInstCountA() const { return InstCount[0]; }
	int64_t getStackSizeA() const { return StackSize[0]; }

	// Accessors for the remarks from the second file.
	int64_t getInstCountB() const { return InstCount[1]; }
	int64_t getStackSizeB() const { return StackSize[1]; }

	/// \returns which files this function was present in.
	FilesPresent getFilesPresent() const {
	if (getInstCountA() == 0)
	return B;
	if (getInstCountB() == 0)
	return A;
	return BOTH;
	}

	FunctionDiff(StringRef FuncName, const InstCountAndStackSize &A,
	const InstCountAndStackSize &B)
	: FuncName(FuncName) {
	InstCount[0] = A.InstCount;
	InstCount[1] = B.InstCount;
	StackSize[0] = A.StackSize;
	StackSize[1] = B.StackSize;
	}
	};

	/// Organizes the diffs into 3 categories:
	/// - Functions which only appeared in the first file
	/// - Functions which only appeared in the second file
	/// - Functions which appeared in both files
	struct DiffsCategorizedByFilesPresent {
	/// Diffs for functions which only appeared in the first file.
	SmallVector<FunctionDiff> OnlyInA;

	/// Diffs for functions which only appeared in the second file.
	SmallVector<FunctionDiff> OnlyInB;

	/// Diffs for functions which appeared in both files.
	SmallVector<FunctionDiff> InBoth;

	/// Add a diff to the appropriate list.
	void addDiff(FunctionDiff &FD) {
	switch (FD.getFilesPresent()) {
	case A:
	OnlyInA.push_back(FD);
	break;
	case B:
	OnlyInB.push_back(FD);
	break;
	case BOTH:
	InBoth.push_back(FD);
	break;
	}
	}
	};

	static void printFunctionDiff(const FunctionDiff &FD, llvm::raw_ostream &OS) {
	// Describe which files the function had remarks in.
	FilesPresent FP = FD.getFilesPresent();
	const std::string &FuncName = FD.FuncName;
	const int64_t InstDiff = FD.getInstDiff();
	assert(InstDiff && "Shouldn't get functions with no size change?");
	const int64_t StackDiff = FD.getStackDiff();
	// Output an indicator denoting which files the function was present in.
	switch (FP) {
	case FilesPresent::A:
	OS << "-- ";
	break;
	case FilesPresent::B:
	OS << "++ ";
	break;
	case FilesPresent::BOTH:
	OS << "== ";
	break;
	}
	// Output an indicator denoting if a function changed in size.
	if (InstDiff > 0)
	OS << "> ";
	else
	OS << "< ";
	OS << FuncName << ", ";
	OS << InstDiff << " instrs, ";
	OS << StackDiff << " stack B";
	OS << "\n";
	}

	/// Print an item in the summary section.
	///
	/// \p TotalA - Total count of the metric in file A.
	/// \p TotalB - Total count of the metric in file B.
	/// \p Metric - Name of the metric we want to print (e.g. instruction
	/// count).
	/// \p OS - The output stream.
	static void printSummaryItem(int64_t TotalA, int64_t TotalB, StringRef Metric,
	llvm::raw_ostream &OS) {
	OS << " " << Metric << ": ";
	int64_t TotalDiff = TotalB - TotalA;
	if (TotalDiff == 0) {
	OS << "None\n";
	return;
	}
	OS << TotalDiff << " (" << formatv("{0:p}", TotalDiff / (double)TotalA)
	<< ")\n";
	}

	/// Print all contents of \p Diff and a high-level summary of the differences.
	static void printDiffsCategorizedByFilesPresent(
	DiffsCategorizedByFilesPresent &DiffsByFilesPresent,
	llvm::raw_ostream &OS) {
	int64_t InstrsA = 0;
	int64_t InstrsB = 0;
	int64_t StackA = 0;
	int64_t StackB = 0;
	// Helper lambda to sort + print a list of diffs.
	auto PrintDiffList = [&](SmallVector<FunctionDiff> &FunctionDiffList) {
	if (FunctionDiffList.empty())
	return;
	stable_sort(FunctionDiffList,
	[](const FunctionDiff &LHS, const FunctionDiff &RHS) {
	return LHS.getInstDiff() < RHS.getInstDiff();
	});
	for (const auto &FuncDiff : FunctionDiffList) {
	// If there is a difference in instruction count, then print out info for
	// the function.
	if (FuncDiff.getInstDiff())
	printFunctionDiff(FuncDiff, OS);
	InstrsA += FuncDiff.getInstCountA();
	InstrsB += FuncDiff.getInstCountB();
	StackA += FuncDiff.getStackSizeA();
	StackB += FuncDiff.getStackSizeB();
	}
	};
	PrintDiffList(DiffsByFilesPresent.OnlyInA);
	PrintDiffList(DiffsByFilesPresent.OnlyInB);
	PrintDiffList(DiffsByFilesPresent.InBoth);
	OS << "\n### Summary ###\n";
	OS << "Total change: \n";
	printSummaryItem(InstrsA, InstrsB, "instruction count", OS);
	printSummaryItem(StackA, StackB, "stack byte usage", OS);
	}

	/// Collects an expected integer value from a given argument index in a remark.
	///
	/// \p Remark - The remark.
	/// \p ArgIdx - The index where the integer value should be found.
	/// \p ExpectedKeyName - The expected key name for the index
	/// (e.g. "InstructionCount")
	///
	/// \returns the integer value at the index if it exists, and the key-value pair
	/// is what is expected. Otherwise, returns an Error.
	static Expected<int64_t> getIntValFromKey(const remarks::Remark &Remark,
	unsigned ArgIdx,
	StringRef ExpectedKeyName) {
	auto KeyName = Remark.Args[ArgIdx].Key;
	if (KeyName != ExpectedKeyName)
	return createStringError(
	inconvertibleErrorCode(),
	Twine("Unexpected key at argument index " + std::to_string(ArgIdx) +
	": Expected '" + ExpectedKeyName + "', got '" + KeyName + "'"));
	long long Val;
	auto ValStr = Remark.Args[ArgIdx].Val;
	if (getAsSignedInteger(ValStr, 0, Val))
	return createStringError(
	inconvertibleErrorCode(),
	Twine("Could not convert string to signed integer: " + ValStr));
	return static_cast<int64_t>(Val);
	}

	/// Collects relevant size information from \p Remark if it is an size-related
	/// remark of some kind (e.g. instruction count). Otherwise records nothing.
	///
	/// \p Remark - The remark.
	/// \p FuncNameToSizeInfo - Maps function names to relevant size info.
	/// \p NumInstCountRemarksParsed - Keeps track of the number of instruction
	/// count remarks parsed. We need at least 1 in both files to produce a diff.
	static Error processRemark(const remarks::Remark &Remark,
	StringMap<InstCountAndStackSize> &FuncNameToSizeInfo,
	unsigned &NumInstCountRemarksParsed) {
	const auto &RemarkName = Remark.RemarkName;
	const auto &PassName = Remark.PassName;
	// Collect remarks which contain the number of instructions in a function.
	if (PassName == "asm-printer" && RemarkName == "InstructionCount") {
	// Expecting the 0-th argument to have the key "NumInstructions" and an
	// integer value.
	auto MaybeInstCount =
	getIntValFromKey(Remark, /ArgIdx = / 0, "NumInstructions");
	if (!MaybeInstCount)
	return MaybeInstCount.takeError();
	FuncNameToSizeInfo[Remark.FunctionName].InstCount = *MaybeInstCount;
	++NumInstCountRemarksParsed;
	}
	// Collect remarks which contain the stack size of a function.
	else if (PassName == "prologepilog" && RemarkName == "StackSize") {
	// Expecting the 0-th argument to have the key "NumStackBytes" and an
	// integer value.
	auto MaybeStackSize =
	getIntValFromKey(Remark, /ArgIdx = / 0, "NumStackBytes");
	if (!MaybeStackSize)
	return MaybeStackSize.takeError();
	FuncNameToSizeInfo[Remark.FunctionName].StackSize = *MaybeStackSize;
	}
	// Either we collected a remark, or it's something we don't care about. In
	// both cases, this is a success.
	return Error::success();
	}

	/// Process all of the size-related remarks in a file.
	///
	/// \param[in] InputFileName - Name of file to read from.
	/// \param[in, out] FuncNameToSizeInfo - Maps function names to relevant
	/// size info.
	static Error readFileAndProcessRemarks(
	StringRef InputFileName,
	StringMap<InstCountAndStackSize> &FuncNameToSizeInfo) {

	auto MaybeBuf = getInputMemoryBuffer(InputFileName);
	if (!MaybeBuf)
	return MaybeBuf.takeError();
	auto MaybeParser =
	createRemarkParserFromMeta(InputFormat, (*MaybeBuf)->getBuffer());
	if (!MaybeParser)
	return MaybeParser.takeError();
	auto &Parser = **MaybeParser;
	auto MaybeRemark = Parser.next();
	unsigned NumInstCountRemarksParsed = 0;
	for (; MaybeRemark; MaybeRemark = Parser.next()) {
	if (auto E = processRemark(**MaybeRemark, FuncNameToSizeInfo,
	NumInstCountRemarksParsed))
	return E;
	}
	auto E = MaybeRemark.takeError();
	if (!E.isA<remarks::EndOfFileError>())
	return E;
	consumeError(std::move(E));
	// We need at least one instruction count remark in each file to produce a
	// meaningful diff.
	if (NumInstCountRemarksParsed == 0)
	return createStringError(
	inconvertibleErrorCode(),
	"File '" + InputFileName +
	"' did not contain any instruction-count remarks!");
	return Error::success();
	}

	/// Wrapper function for readFileAndProcessRemarks which handles errors.
	///
	/// \param[in] InputFileName - Name of file to read from.
	/// \param[out] FuncNameToSizeInfo - Populated with information from size
	/// remarks in the input file.
	///
	/// \returns true if readFileAndProcessRemarks returned no errors. False
	/// otherwise.
	static Error tryReadFileAndProcessRemarks(
	StringRef InputFileName,
	StringMap<InstCountAndStackSize> &FuncNameToSizeInfo) {
	if (Error E = readFileAndProcessRemarks(InputFileName, FuncNameToSizeInfo)) {
	return E;
	}
	return Error::success();
	}

	/// Populates \p FuncDiffs with the difference between \p
	/// FuncNameToSizeInfoA and \p FuncNameToSizeInfoB.
	///
	/// \param[in] FuncNameToSizeInfoA - Size info collected from the first
	/// remarks file.
	/// \param[in] FuncNameToSizeInfoB - Size info collected from
	/// the second remarks file.
	/// \param[out] DiffsByFilesPresent - Filled with the diff between \p
	/// FuncNameToSizeInfoA and \p FuncNameToSizeInfoB.
	static void
	computeDiff(const StringMap<InstCountAndStackSize> &FuncNameToSizeInfoA,
	const StringMap<InstCountAndStackSize> &FuncNameToSizeInfoB,
	DiffsCategorizedByFilesPresent &DiffsByFilesPresent) {
	SmallSet<std::string, 10> FuncNames;
	for (const auto &FuncName : FuncNameToSizeInfoA.keys())
	FuncNames.insert(FuncName.str());
	for (const auto &FuncName : FuncNameToSizeInfoB.keys())
	FuncNames.insert(FuncName.str());
	for (const std::string &FuncName : FuncNames) {
	const auto &SizeInfoA = FuncNameToSizeInfoA.lookup(FuncName);
	const auto &SizeInfoB = FuncNameToSizeInfoB.lookup(FuncName);
	FunctionDiff FuncDiff(FuncName, SizeInfoA, SizeInfoB);
	DiffsByFilesPresent.addDiff(FuncDiff);
	}
	}

	/// Attempt to get the output stream for writing the diff.
	static ErrorOr<std::unique_ptr<ToolOutputFile>> getOutputStream() {
	if (OutputFilename == "")
	OutputFilename = "-";
	std::error_code EC;
	auto Out = std::make_unique<ToolOutputFile>(OutputFilename, EC,
	sys::fs::OF_TextWithCRLF);
	if (!EC)
	return std::move(Out);
	return EC;
	}

	/// \return a json::Array representing all FunctionDiffs in \p FunctionDiffs.
	/// \p WhichFiles represents which files the functions in \p FunctionDiffs
	/// appeared in (A, B, or both).
	json::Array
	getFunctionDiffListAsJSON(const SmallVector<FunctionDiff> &FunctionDiffs,
	const FilesPresent &WhichFiles) {
	json::Array FunctionDiffsAsJSON;
	int64_t InstCountA, InstCountB, StackSizeA, StackSizeB;
	for (auto &Diff : FunctionDiffs) {
	InstCountA = InstCountB = StackSizeA = StackSizeB = 0;
	switch (WhichFiles) {
	case BOTH:
	[[fallthrough]];
	case A:
	InstCountA = Diff.getInstCountA();
	StackSizeA = Diff.getStackSizeA();
	if (WhichFiles != BOTH)
	break;
	[[fallthrough]];
	case B:
	InstCountB = Diff.getInstCountB();
	StackSizeB = Diff.getStackSizeB();
	break;
	}
	// Each metric we care about is represented like:
	// "Val": [A, B]
	// This allows any consumer of the JSON to calculate the diff using B - A.
	// This is somewhat wasteful for OnlyInA and OnlyInB (we only need A or B).
	// However, this should make writing consuming tools easier, since the tool
	// writer doesn't need to think about slightly different formats in each
	// section.
	json::Object FunctionObject({{"FunctionName", Diff.FuncName},
	{"InstCount", {InstCountA, InstCountB}},
	{"StackSize", {StackSizeA, StackSizeB}}});
	FunctionDiffsAsJSON.push_back(std::move(FunctionObject));
	}
	return FunctionDiffsAsJSON;
	}

	/// Output all diffs in \p DiffsByFilesPresent as a JSON report. This is
	/// intended for consumption by external tools.
	///
	/// \p InputFileNameA - File A used to produce the report.
	/// \p InputFileNameB - File B used ot produce the report.
	/// \p OS - Output stream.
	///
	/// JSON output includes:
	/// - \p InputFileNameA and \p InputFileNameB under "Files".
	/// - Functions present in both files under "InBoth".
	/// - Functions present only in A in "OnlyInA".
	/// - Functions present only in B in "OnlyInB".
	/// - Instruction count and stack size differences for each function.
	///
	/// Differences are represented using [count_a, count_b]. The actual difference
	/// can be computed via count_b - count_a.
	static void
	outputJSONForAllDiffs(StringRef InputFileNameA, StringRef InputFileNameB,
	const DiffsCategorizedByFilesPresent &DiffsByFilesPresent,
	llvm::raw_ostream &OS) {
	json::Object Output;
	// Include file names in the report.
	json::Object Files(
	{{"A", InputFileNameA.str()}, {"B", InputFileNameB.str()}});
	Output["Files"] = std::move(Files);
	Output["OnlyInA"] = getFunctionDiffListAsJSON(DiffsByFilesPresent.OnlyInA, A);
	Output["OnlyInB"] = getFunctionDiffListAsJSON(DiffsByFilesPresent.OnlyInB, B);
	Output["InBoth"] =
	getFunctionDiffListAsJSON(DiffsByFilesPresent.InBoth, BOTH);
	json::OStream JOS(OS, PrettyPrint ? 2 : 0);
	JOS.value(std::move(Output));
	OS << '\n';
	}

	/// Output all diffs in \p DiffsByFilesPresent using the desired output style.
	/// \returns Error::success() on success, and an Error otherwise.
	/// \p InputFileNameA - Name of input file A; may be used in the report.
	/// \p InputFileNameB - Name of input file B; may be used in the report.
	static Error
	outputAllDiffs(StringRef InputFileNameA, StringRef InputFileNameB,
	DiffsCategorizedByFilesPresent &DiffsByFilesPresent) {
	auto MaybeOF = getOutputStream();
	if (std::error_code EC = MaybeOF.getError())
	return errorCodeToError(EC);
	std::unique_ptr<ToolOutputFile> OF = std::move(*MaybeOF);
	switch (ReportStyle) {
	case human_output:
	printDiffsCategorizedByFilesPresent(DiffsByFilesPresent, OF->os());
	break;
	case json_output:
	outputJSONForAllDiffs(InputFileNameA, InputFileNameB, DiffsByFilesPresent,
	OF->os());
	break;
	}
	OF->keep();
	return Error::success();
	}

	/// Boolean wrapper for outputDiff which handles errors.
	static Error
	tryOutputAllDiffs(StringRef InputFileNameA, StringRef InputFileNameB,
	DiffsCategorizedByFilesPresent &DiffsByFilesPresent) {
	if (Error E =
	outputAllDiffs(InputFileNameA, InputFileNameB, DiffsByFilesPresent)) {
	return E;
	}
	return Error::success();
	}

	static Error trySizeSiff() {
	StringMap<InstCountAndStackSize> FuncNameToSizeInfoA;
	StringMap<InstCountAndStackSize> FuncNameToSizeInfoB;
	if (auto E =
	tryReadFileAndProcessRemarks(InputFileNameA, FuncNameToSizeInfoA))
	return E;
	if (auto E =
	tryReadFileAndProcessRemarks(InputFileNameB, FuncNameToSizeInfoB))
	return E;
	DiffsCategorizedByFilesPresent DiffsByFilesPresent;
	computeDiff(FuncNameToSizeInfoA, FuncNameToSizeInfoB, DiffsByFilesPresent);
	if (auto E = tryOutputAllDiffs(InputFileNameA, InputFileNameB,
	DiffsByFilesPresent))
	return E;
	return Error::success();
	}

	static CommandRegistration RemarkSizeSiffRegister(&RemarkSizeDiffUtil,
	trySizeSiff);