Index: compiler-rt/trunk/lib/xray/tests/unit/fdr_controller_test.cc
===================================================================
--- compiler-rt/trunk/lib/xray/tests/unit/fdr_controller_test.cc
+++ compiler-rt/trunk/lib/xray/tests/unit/fdr_controller_test.cc
@@ -137,6 +137,30 @@
                 TSCIs(Gt(1000uL))))));
 }
 
+TEST_F(FunctionSequenceTest, PreservedCallsSupportLargeDeltas) {
+  C = llvm::make_unique<FDRController<>>(BQ.get(), B, *W, clock_gettime, 1000);
+  uint64_t TSC = 1;
+  uint16_t CPU = 0;
+  const auto LargeDelta = uint64_t{std::numeric_limits<int32_t>::max()};
+  ASSERT_TRUE(C->functionEnter(1, TSC++, CPU));
+  ASSERT_TRUE(C->functionExit(1, TSC += LargeDelta, CPU));
+  ASSERT_TRUE(C->flush());
+  ASSERT_EQ(BQ->finalize(), BufferQueue::ErrorCode::Ok);
+
+  // Serialize the buffer then test to see if we find the right TSC with a large
+  // delta.
+  std::string Serialized = serialize(*BQ, 3);
+  llvm::DataExtractor DE(Serialized, true, 8);
+  auto TraceOrErr = llvm::xray::loadTrace(DE);
+  EXPECT_THAT_EXPECTED(
+      TraceOrErr,
+      HasValue(ElementsAre(
+          AllOf(FuncId(1), RecordType(llvm::xray::RecordTypes::ENTER),
+                TSCIs(Eq(1uL))),
+          AllOf(FuncId(1), RecordType(llvm::xray::RecordTypes::EXIT),
+                TSCIs(Gt(LargeDelta))))));
+}
+
 TEST_F(FunctionSequenceTest, RewindingMultipleCalls) {
   C = llvm::make_unique<FDRController<>>(BQ.get(), B, *W, clock_gettime, 1000);
 
Index: compiler-rt/trunk/lib/xray/xray_fdr_controller.h
===================================================================
--- compiler-rt/trunk/lib/xray/xray_fdr_controller.h
+++ compiler-rt/trunk/lib/xray/xray_fdr_controller.h
@@ -13,6 +13,7 @@
 #ifndef COMPILER_RT_LIB_XRAY_XRAY_FDR_CONTROLLER_H_
 #define COMPILER_RT_LIB_XRAY_XRAY_FDR_CONTROLLER_H_
 
+#include <limits>
 #include <time.h>
 
 #include "xray/xray_interface.h"
@@ -158,8 +159,14 @@
       return PreambleResult::WroteMetadata;
     }
 
-    if (UNLIKELY(LatestCPU == LatestCPU && LatestTSC > TSC)) {
-      // The TSC has wrapped around, from the last TSC we've seen.
+    DCHECK_EQ(LatestCPU, CPU);
+
+    if (UNLIKELY(LatestTSC > TSC ||
+                 TSC - LatestTSC >
+                     uint64_t{std::numeric_limits<int32_t>::max()})) {
+      // Either the TSC has wrapped around from the last TSC we've seen or the
+      // delta is too large to fit in a 32-bit signed integer, so we write a
+      // wrap-around record.
       LatestTSC = TSC;
 
       if (B.Generation != BQ->generation())
@@ -248,10 +255,11 @@
     UndoableFunctionEnters = (PreambleStatus == PreambleResult::WroteMetadata)
                                  ? 1
                                  : UndoableFunctionEnters + 1;
+    auto Delta = TSC - LatestTSC;
     LastFunctionEntryTSC = TSC;
     LatestTSC = TSC;
     return W.writeFunction(FDRLogWriter::FunctionRecordKind::Enter,
-                           mask(FuncId), TSC - LatestTSC);
+                           mask(FuncId), Delta);
   }
 
   bool functionTailExit(int32_t FuncId, uint64_t TSC,
@@ -273,9 +281,10 @@
 
     UndoableTailExits = UndoableFunctionEnters ? UndoableTailExits + 1 : 0;
     UndoableFunctionEnters = 0;
+    auto Delta = TSC - LatestTSC;
     LatestTSC = TSC;
     return W.writeFunction(FDRLogWriter::FunctionRecordKind::TailExit,
-                           mask(FuncId), TSC - LatestTSC);
+                           mask(FuncId), Delta);
   }
 
   bool functionEnterArg(int32_t FuncId, uint64_t TSC, uint16_t CPU,
@@ -285,13 +294,14 @@
         functionPreamble(TSC, CPU) == PreambleResult::InvalidBuffer)
       return returnBuffer();
 
+    auto Delta = TSC - LatestTSC;
     LatestTSC = TSC;
     LastFunctionEntryTSC = 0;
     UndoableFunctionEnters = 0;
     UndoableTailExits = 0;
 
     W.writeFunction(FDRLogWriter::FunctionRecordKind::EnterArg, mask(FuncId),
-                    TSC - LatestTSC);
+                    Delta);
     return W.writeMetadata<MetadataRecord::RecordKinds::CallArgument>(Arg);
   }
 
Index: llvm/trunk/lib/XRay/RecordPrinter.cpp
===================================================================
--- llvm/trunk/lib/XRay/RecordPrinter.cpp
+++ llvm/trunk/lib/XRay/RecordPrinter.cpp
@@ -66,19 +66,19 @@
   // FIXME: Support symbolization here?
   switch (R.recordType()) {
   case RecordTypes::ENTER:
-    OS << formatv("<Function Enter: #{0} delta = +{0}>", R.functionId(),
+    OS << formatv("<Function Enter: #{0} delta = +{1}>", R.functionId(),
                   R.delta());
     break;
   case RecordTypes::ENTER_ARG:
-    OS << formatv("<Function Enter With Arg: #{0} delta = +{0}>",
+    OS << formatv("<Function Enter With Arg: #{0} delta = +{1}>",
                   R.functionId(), R.delta());
     break;
   case RecordTypes::EXIT:
-    OS << formatv("<Function Exit: #{0} delta = +{0}>", R.functionId(),
+    OS << formatv("<Function Exit: #{0} delta = +{1}>", R.functionId(),
                   R.delta());
     break;
   case RecordTypes::TAIL_EXIT:
-    OS << formatv("<Function Tail Exit: #{0} delta = +{0}>", R.functionId(),
+    OS << formatv("<Function Tail Exit: #{0} delta = +{1}>", R.functionId(),
                   R.delta());
     break;
   }