Index: llvm/include/llvm/XRay/FDRRecordConsumer.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/XRay/FDRRecordConsumer.h
@@ -0,0 +1,55 @@
+//===- FDRRecordConsumer.h - XRay Flight Data Recorder Mode Records -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_INCLUDE_LLVM_XRAY_FDRRECORDCONSUMER_H_
+#define LLVM_INCLUDE_LLVM_XRAY_FDRRECORDCONSUMER_H_
+
+#include "llvm/Support/Error.h"
+#include "llvm/XRay/FDRRecords.h"
+#include <algorithm>
+#include <memory>
+#include <vector>
+
+namespace llvm {
+namespace xray {
+
+class RecordConsumer {
+public:
+  virtual Error consume(std::unique_ptr<Record> R) = 0;
+  virtual ~RecordConsumer() = default;
+};
+
+// This consumer will collect all the records into a vector of records, in
+// arrival order.
+class LogBuilderConsumer : public RecordConsumer {
+  std::vector<std::unique_ptr<Record>> &Records;
+
+public:
+  explicit LogBuilderConsumer(std::vector<std::unique_ptr<Record>> &R)
+      : RecordConsumer(), Records(R) {}
+
+  Error consume(std::unique_ptr<Record> R) override;
+};
+
+// A PipelineConsumer applies a set of visitors to every consumed Record, in the
+// order by which the visitors are added to the pipeline in the order of
+// appearance.
+class PipelineConsumer : public RecordConsumer {
+  std::vector<RecordVisitor *> Visitors;
+
+public:
+  PipelineConsumer(std::initializer_list<RecordVisitor *> V)
+      : RecordConsumer(), Visitors(V) {}
+
+  Error consume(std::unique_ptr<Record> R) override;
+};
+
+} // namespace xray
+} // namespace llvm
+
+#endif // LLVM_INCLUDE_LLVM_XRAY_FDRRECORDCONSUMER_H_
Index: llvm/include/llvm/XRay/FDRRecordProducer.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/XRay/FDRRecordProducer.h
@@ -0,0 +1,46 @@
+//===- FDRRecordProducer.h - XRay FDR Mode Record Producer ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_INCLUDE_LLVM_XRAY_FDRRECORDPRODUCER_H_
+#define LLVM_INCLUDE_LLVM_XRAY_FDRRECORDPRODUCER_H_
+
+#include "llvm/Support/Error.h"
+#include "llvm/XRay/FDRRecords.h"
+#include "llvm/XRay/XRayRecord.h"
+#include <memory>
+
+namespace llvm {
+namespace xray {
+
+class RecordProducer {
+public:
+  /// All producer implementations must yield either an Error or a non-nullptr
+  /// unique_ptr<Record>.
+  virtual Expected<std::unique_ptr<Record>> produce() = 0;
+  virtual ~RecordProducer() = default;
+};
+
+class FileBasedRecordProducer : public RecordProducer {
+  const XRayFileHeader &Header;
+  DataExtractor &E;
+  uint32_t &OffsetPtr;
+
+public:
+  FileBasedRecordProducer(const XRayFileHeader &FH, DataExtractor &DE,
+                          uint32_t &OP)
+      : Header(FH), E(DE), OffsetPtr(OP) {}
+
+  /// This producer encapsulates the logic for loading a File-backed
+  /// RecordProducer hidden behind a DataExtractor.
+  Expected<std::unique_ptr<Record>> produce() override;
+};
+
+} // namespace xray
+} // namespace llvm
+
+#endif // LLVM_INCLUDE_LLVM_XRAY_FDRRECORDPRODUCER_H_
Index: llvm/lib/XRay/CMakeLists.txt
===================================================================
--- llvm/lib/XRay/CMakeLists.txt
+++ llvm/lib/XRay/CMakeLists.txt
@@ -1,8 +1,10 @@
 add_llvm_library(LLVMXRay
+  FDRRecordProducer.cpp
   FDRRecords.cpp
   FDRTraceWriter.cpp
   FileHeaderReader.cpp
   InstrumentationMap.cpp
+  LogBuilderConsumer.cpp
   RecordInitializer.cpp
   Trace.cpp
 
Index: llvm/lib/XRay/FDRRecordProducer.cpp
===================================================================
--- /dev/null
+++ llvm/lib/XRay/FDRRecordProducer.cpp
@@ -0,0 +1,87 @@
+//===- FDRRecordProducer.cpp - XRay FDR Mode Record Producer --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/XRay/FDRRecordProducer.h"
+#include "llvm/Support/DataExtractor.h"
+
+namespace llvm {
+namespace xray {
+
+Expected<std::unique_ptr<Record>> FileBasedRecordProducer::produce() {
+  // At the top level, we read one byte to determine the type of the record to
+  // create. This byte will comprise of the following bits:
+  //
+  //   - offset 0: A '1' indicates a metadata record, a '0' indicates a function
+  //     record.
+  //   - offsets 1-7: For metadata records, this will indicate the kind of
+  //     metadata record should be loaded.
+  //
+  // We read first byte, then create the appropriate type of record to consume
+  // the rest of the bytes.
+  auto PreReadOffset = OffsetPtr;
+  uint8_t FirstByte = E.getU8(&OffsetPtr);
+  std::unique_ptr<Record> R;
+
+  // For metadata records, handle especially here.
+  if (FirstByte & 0x01) {
+    // FIXME: Use a registry, and dispatch based on record types more
+    // automatically.
+    switch (FirstByte >> 1) {
+    case 0: // New buffer record.
+      R = llvm::make_unique<NewBufferRecord>();
+      break;
+    case 1: // End of buffer record.
+      if (Header.Version >= 2)
+        return createStringError(
+            std::make_error_code(std::errc::executable_format_error),
+            "End of buffer records are no longer supported starting version "
+            "2 of the log. Found at offset %d.",
+            PreReadOffset);
+      R = llvm::make_unique<EndBufferRecord>();
+      break;
+    case 2: // New CPU Id record.
+      R = llvm::make_unique<NewCPUIDRecord>();
+      break;
+    case 3: // TSC Wrap record.
+      R = llvm::make_unique<TSCWrapRecord>();
+      break;
+    case 4: // Wall Clock record.
+      R = llvm::make_unique<WallclockRecord>();
+      break;
+    case 5: // Custom event marker and record.
+      R = llvm::make_unique<CustomEventRecord>();
+      break;
+    case 6: // Call argument record.
+      R = llvm::make_unique<CallArgRecord>();
+      break;
+    case 7: // Buffer extents record.
+      R = llvm::make_unique<BufferExtents>();
+      break;
+    case 9: // PID record.
+      R = llvm::make_unique<PIDRecord>();
+      break;
+    default: // Unknown record.
+      return createStringError(
+          std::make_error_code(std::errc::executable_format_error),
+          "Encountered an unsupported metadata record (%d) at offset %d.",
+          FirstByte >> 1, PreReadOffset);
+    }
+  } else {
+    R = llvm::make_unique<FunctionRecord>();
+  }
+  RecordInitializer RI(E, OffsetPtr);
+
+  if (auto Err = R->apply(RI))
+    return std::move(Err);
+
+  assert(R != nullptr);
+  return std::move(R);
+}
+
+} // namespace xray
+} // namespace llvm
Index: llvm/lib/XRay/FDRTraceWriter.cpp
===================================================================
--- llvm/lib/XRay/FDRTraceWriter.cpp
+++ llvm/lib/XRay/FDRTraceWriter.cpp
@@ -69,6 +69,7 @@
   MetadataBlob B;
   B.Type = 1;
   B.RecordKind = Kind;
+  std::memset(B.Data, 0, sizeof(B.Data));
   IndexedMemcpy<0>::Copy(B.Data, std::make_tuple(Ds...));
   OS.write(reinterpret_cast<const char *>(&B), sizeof(MetadataBlob));
   return Error::success();
Index: llvm/lib/XRay/LogBuilderConsumer.cpp
===================================================================
--- /dev/null
+++ llvm/lib/XRay/LogBuilderConsumer.cpp
@@ -0,0 +1,38 @@
+//===- FDRRecordConsumer.h - XRay Flight Data Recorder Mode Records -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/XRay/FDRRecordConsumer.h"
+
+namespace llvm {
+namespace xray {
+
+Error LogBuilderConsumer::consume(std::unique_ptr<Record> R) {
+  if (!R)
+    return createStringError(
+        std::make_error_code(std::errc::invalid_argument),
+        "Must not call RecordConsumer::consume() with a null pointer.");
+  Records.push_back(std::move(R));
+  return Error::success();
+}
+
+Error PipelineConsumer::consume(std::unique_ptr<Record> R) {
+  if (!R)
+    return createStringError(
+        std::make_error_code(std::errc::invalid_argument),
+        "Must not call RecordConsumer::consume() with a null pointer.");
+
+  // We apply all of the visitors in order, and concatenate errors
+  // appropriately.
+  Error Result = Error::success();
+  for (auto *V : Visitors)
+    Result = joinErrors(std::move(Result), R->apply(*V));
+  return Result;
+}
+
+} // namespace xray
+} // namespace llvm
Index: llvm/unittests/XRay/CMakeLists.txt
===================================================================
--- llvm/unittests/XRay/CMakeLists.txt
+++ llvm/unittests/XRay/CMakeLists.txt
@@ -4,6 +4,7 @@
   )
 
 add_llvm_unittest(XRayTests
+  FDRProducerConsumerTest.cpp
   FDRTraceWriterTest.cpp
   GraphTest.cpp
   )
Index: llvm/unittests/XRay/FDRProducerConsumerTest.cpp
===================================================================
--- /dev/null
+++ llvm/unittests/XRay/FDRProducerConsumerTest.cpp
@@ -0,0 +1,141 @@
+//===- llvm/unittest/XRay/FDRProducerConsumerTest.cpp -----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Test for round-trip record writing and reading.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/XRay/FDRLogBuilder.h"
+#include "llvm/XRay/FDRRecordConsumer.h"
+#include "llvm/XRay/FDRRecordProducer.h"
+#include "llvm/XRay/FDRRecords.h"
+#include "llvm/XRay/FDRTraceWriter.h"
+#include "llvm/XRay/FileHeaderReader.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include <string>
+#include <tuple>
+
+namespace llvm {
+namespace xray {
+namespace {
+
+using ::testing::Eq;
+using ::testing::IsEmpty;
+using ::testing::Not;
+
+template <class RecordType> std::unique_ptr<Record> MakeRecord();
+
+template <> std::unique_ptr<Record> MakeRecord<BufferExtents>() {
+  return make_unique<BufferExtents>(1);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<NewBufferRecord>() {
+  return make_unique<NewBufferRecord>(1);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<NewCPUIDRecord>() {
+  return make_unique<NewCPUIDRecord>(1);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<TSCWrapRecord>() {
+  return make_unique<TSCWrapRecord>(1);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<WallclockRecord>() {
+  return make_unique<WallclockRecord>(1, 2);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<CustomEventRecord>() {
+  return make_unique<CustomEventRecord>(4, 1, "data");
+}
+
+template <> std::unique_ptr<Record> MakeRecord<CallArgRecord>() {
+  return make_unique<CallArgRecord>(1);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<PIDRecord>() {
+  return make_unique<PIDRecord>(1);
+}
+
+template <> std::unique_ptr<Record> MakeRecord<FunctionRecord>() {
+  return make_unique<FunctionRecord>(RecordTypes::ENTER, 1, 2);
+}
+
+template <class T> class RoundTripTest : public ::testing::Test {
+public:
+  RoundTripTest() : Data(), OS(Data) {
+    H.Version = 3;
+    H.Type = 1;
+    H.ConstantTSC = true;
+    H.NonstopTSC = true;
+    H.CycleFrequency = 3e9;
+
+    Writer = make_unique<FDRTraceWriter>(OS, H);
+    Record = MakeRecord<T>();
+  }
+
+protected:
+  std::string Data;
+  raw_string_ostream OS;
+  XRayFileHeader H;
+  std::unique_ptr<FDRTraceWriter> Writer;
+  std::unique_ptr<Record> Record;
+};
+
+TYPED_TEST_CASE_P(RoundTripTest);
+
+// This test ensures that the writing and reading implementations are in sync --
+// that given write(read(write(R))) == R.
+TYPED_TEST_P(RoundTripTest, RoundTripsSingleValue) {
+  auto &R = this->Record;
+  ASSERT_FALSE(errorToBool(R->apply(*this->Writer)));
+  this->OS.flush();
+
+  DataExtractor DE(this->Data, true, 8);
+  uint32_t OffsetPtr = 0;
+  auto HeaderOrErr = readBinaryFormatHeader(DE, OffsetPtr);
+  if (!HeaderOrErr)
+    FAIL() << HeaderOrErr.takeError();
+
+  FileBasedRecordProducer P(HeaderOrErr.get(), DE, OffsetPtr);
+  std::vector<std::unique_ptr<Record>> Records;
+  LogBuilderConsumer C(Records);
+  while (DE.isValidOffsetForDataOfSize(OffsetPtr, 1)) {
+    auto R = P.produce();
+    if (!R)
+      FAIL() << R.takeError();
+    if (auto E = C.consume(std::move(R.get())))
+      FAIL() << E;
+  }
+  ASSERT_THAT(Records, Not(IsEmpty()));
+  std::string Data2;
+  raw_string_ostream OS2(Data2);
+  FDRTraceWriter Writer2(OS2, this->H);
+  for (auto &P : Records)
+    ASSERT_FALSE(errorToBool(P->apply(Writer2)));
+  OS2.flush();
+
+  EXPECT_EQ(Data2.substr(sizeof(XRayFileHeader)),
+            this->Data.substr(sizeof(XRayFileHeader)));
+  EXPECT_THAT(Records[0]->type(), Eq(R->type()));
+}
+
+REGISTER_TYPED_TEST_CASE_P(RoundTripTest, RoundTripsSingleValue);
+
+using RecordTypes =
+    ::testing::Types<BufferExtents, NewBufferRecord, NewCPUIDRecord,
+                     TSCWrapRecord, WallclockRecord, CustomEventRecord,
+                     CallArgRecord, BufferExtents, PIDRecord, FunctionRecord>;
+INSTANTIATE_TYPED_TEST_CASE_P(Records, RoundTripTest, RecordTypes);
+
+} // namespace
+} // namespace xray
+} // namespace llvm