Index: llvm/trunk/lib/XRay/Trace.cpp
===================================================================
--- llvm/trunk/lib/XRay/Trace.cpp
+++ llvm/trunk/lib/XRay/Trace.cpp
@@ -82,29 +82,59 @@
   for (auto S = Data.drop_front(32); !S.empty(); S = S.drop_front(32)) {
     DataExtractor RecordExtractor(S, true, 8);
     uint32_t OffsetPtr = 0;
-    Records.emplace_back();
-    auto &Record = Records.back();
-    Record.RecordType = RecordExtractor.getU16(&OffsetPtr);
-    Record.CPU = RecordExtractor.getU8(&OffsetPtr);
-    auto Type = RecordExtractor.getU8(&OffsetPtr);
-    switch (Type) {
-    case 0:
-      Record.Type = RecordTypes::ENTER;
-      break;
-    case 1:
-      Record.Type = RecordTypes::EXIT;
+    switch (auto RecordType = RecordExtractor.getU16(&OffsetPtr)) {
+    case 0: { // Normal records.
+      Records.emplace_back();
+      auto &Record = Records.back();
+      Record.RecordType = RecordType;
+      Record.CPU = RecordExtractor.getU8(&OffsetPtr);
+      auto Type = RecordExtractor.getU8(&OffsetPtr);
+      switch (Type) {
+      case 0:
+        Record.Type = RecordTypes::ENTER;
+        break;
+      case 1:
+        Record.Type = RecordTypes::EXIT;
+        break;
+      case 2:
+        Record.Type = RecordTypes::TAIL_EXIT;
+        break;
+      case 3:
+        Record.Type = RecordTypes::ENTER_ARG;
+        break;
+      default:
+        return make_error<StringError>(
+            Twine("Unknown record type '") + Twine(int{Type}) + "'",
+            std::make_error_code(std::errc::executable_format_error));
+      }
+      Record.FuncId = RecordExtractor.getSigned(&OffsetPtr, sizeof(int32_t));
+      Record.TSC = RecordExtractor.getU64(&OffsetPtr);
+      Record.TId = RecordExtractor.getU32(&OffsetPtr);
       break;
-    case 2:
-      Record.Type = RecordTypes::TAIL_EXIT;
+    }
+    case 1: { // Arg payload record.
+      auto &Record = Records.back();
+      // Advance two bytes to avoid padding.
+      OffsetPtr += 2;
+      int32_t FuncId = RecordExtractor.getSigned(&OffsetPtr, sizeof(int32_t));
+      auto TId = RecordExtractor.getU32(&OffsetPtr);
+      if (Record.FuncId != FuncId || Record.TId != TId)
+        return make_error<StringError>(
+            Twine("Corrupted log, found payload following non-matching "
+                  "function + thread record. Record for ") +
+                Twine(Record.FuncId) + " != " + Twine(FuncId),
+            std::make_error_code(std::errc::executable_format_error));
+      // Advance another four bytes to avoid padding.
+      OffsetPtr += 4;
+      auto Arg = RecordExtractor.getU64(&OffsetPtr);
+      Record.CallArgs.push_back(Arg);
       break;
+    }
     default:
       return make_error<StringError>(
-          Twine("Unknown record type '") + Twine(int{Type}) + "'",
+          Twine("Unknown record type == ") + Twine(RecordType),
           std::make_error_code(std::errc::executable_format_error));
     }
-    Record.FuncId = RecordExtractor.getSigned(&OffsetPtr, sizeof(int32_t));
-    Record.TSC = RecordExtractor.getU64(&OffsetPtr);
-    Record.TId = RecordExtractor.getU32(&OffsetPtr);
   }
   return Error::success();
 }
@@ -234,8 +264,8 @@
   uint32_t DataSize = RecordExtractor.getU32(&OffsetPtr);
   uint64_t TSC = RecordExtractor.getU64(&OffsetPtr);
 
-  // FIXME: Actually represent the record through the API. For now we only skip
-  // through the data.
+  // FIXME: Actually represent the record through the API. For now we only
+  // skip through the data.
   (void)TSC;
   RecordSize = 16 + DataSize;
   return Error::success();
@@ -507,8 +537,8 @@
   Records.clear();
   std::transform(Trace.Records.begin(), Trace.Records.end(),
                  std::back_inserter(Records), [&](const YAMLXRayRecord &R) {
-                   return XRayRecord{R.RecordType, R.CPU, R.Type,
-                                     R.FuncId,     R.TSC, R.TId, R.CallArgs};
+                   return XRayRecord{R.RecordType, R.CPU, R.Type,    R.FuncId,
+                                     R.TSC,        R.TId, R.CallArgs};
                  });
   return Error::success();
 }
Index: llvm/trunk/test/tools/llvm-xray/X86/convert-basic-arg1-to-yaml.txt
===================================================================
--- llvm/trunk/test/tools/llvm-xray/X86/convert-basic-arg1-to-yaml.txt
+++ llvm/trunk/test/tools/llvm-xray/X86/convert-basic-arg1-to-yaml.txt
@@ -0,0 +1,15 @@
+; RUN: llvm-xray convert %S/Inputs/naive-with-arg1-entries.xray -f=yaml -o - | FileCheck %s
+
+; CHECK:      ---
+; CHECK-NEXT: header:
+; CHECK-NEXT:   version:         2
+; CHECK-NEXT:   type:            0
+; CHECK-NEXT:   constant-tsc:    true
+; CHECK-NEXT:   nonstop-tsc:     true
+; CHECK-NEXT:   cycle-frequency: 3500000000
+; CHECK-NEXT: records:
+; CHECK-NEXT:   - { type: 0, func-id: 1, function: '1', cpu: 17, thread: 8715, kind: function-enter, tsc: 22555670288232728 }
+; CHECK-NEXT:   - { type: 0, func-id: 1, function: '1', cpu: 17, thread: 8715, kind: function-exit, tsc: 22555670288334784 }
+; CHECK-NEXT:   - { type: 0, func-id: 2, function: '2', args: [ 1 ], cpu: 17, thread: 8715, kind: function-enter-arg, tsc: 22555670288335768 }
+; CHECK-NEXT:   - { type: 0, func-id: 2, function: '2', cpu: 17, thread: 8715, kind: function-exit, tsc: 22555670288365224 }
+; CHECK-NEXT: ...