Index: llvm/CMakeLists.txt
===================================================================
--- llvm/CMakeLists.txt
+++ llvm/CMakeLists.txt
@@ -860,6 +860,7 @@
   add_subdirectory(utils/PerfectShuffle)
   add_subdirectory(utils/count)
   add_subdirectory(utils/not)
+  add_subdirectory(utils/trace)
   add_subdirectory(utils/yaml-bench)
 else()
   if ( LLVM_INCLUDE_TESTS )
Index: llvm/test/Support/execute.test
===================================================================
--- /dev/null
+++ llvm/test/Support/execute.test
@@ -0,0 +1,42 @@
+; RUN: rm -f %t.stdout
+; RUN: trace -execfile=%s 2>&1 | FileCheck -check-prefix=NONE_REDIRECTED %s
+; RUN: trace -stdout=%t.stdout -execfile=%s 2>&1 | FileCheck -check-prefix=STDOUT_REDIRECTED %s
+; RUN: FileCheck -input-file=%t.stdout -check-prefix=STDOUT_CONTENTS %s
+; RUN: rm -f %t.stderr
+; RUN: trace -stderr=%t.stderr -execfile=%s 2>&1 | FileCheck -check-prefix=STDERR_REDIRECTED %s
+; RUN: FileCheck -input-file=%t.stderr -check-prefix=STDERR_CONTENTS %s
+; RUN: rm -f %t.stdout %t.stderr
+; RUN: trace -stdout=%t.stdout -stderr=%t.stderr -execfile=%s 2>&1 | FileCheck -check-prefix=BOTH_REDIRECTED %s
+; RUN: FileCheck -input-file=%t.stdout -check-prefix=STDOUT_CONTENTS %s
+; RUN: FileCheck -input-file=%t.stderr -check-prefix=STDERR_CONTENTS %s
+
+
+write stdout This goes to stdout
+write stderr This goes to stderr
+exit 42
+
+; NONE_REDIRECTED:      PARENT(stdout): Running
+; NONE_REDIRECTED-NEXT: CHILD(stdout): Running
+; NONE_REDIRECTED-NEXT: CHILD(stdout): This goes to stdout
+; NONE_REDIRECTED-NEXT: CHILD(stderr): This goes to stderr
+; NONE_REDIRECTED-NEXT: CHILD(stdout): exiting with code 42
+; NONE_REDIRECTED-NEXT: PARENT(stdout): Child exited with code 42
+
+; STDOUT_REDIRECTED:      PARENT(stdout): Running
+; STDOUT_REDIRECTED-NEXT: CHILD(stderr): This goes to stderr
+; STDOUT_REDIRECTED-NEXT: PARENT(stdout): Child exited with code 42
+
+; STDOUT_CONTENTS:      CHILD(stdout): Running
+; STDOUT_CONTENTS-NEXT: CHILD(stdout): This goes to stdout
+; STDOUT_CONTENTS-NEXT: CHILD(stdout): exiting with code 42
+
+; STDERR_REDIRECTED:      PARENT(stdout): Running
+; STDERR_REDIRECTED-NEXT: CHILD(stdout): Running
+; STDERR_REDIRECTED-NEXT: CHILD(stdout): This goes to stdout
+; STDERR_REDIRECTED-NEXT: CHILD(stdout): exiting with code 42
+; STDERR_REDIRECTED-NEXT: PARENT(stdout): Child exited with code 42
+
+; STDERR_CONTENTS: CHILD(stderr): This goes to stderr
+
+; BOTH_REDIRECTED:      PARENT(stdout): Running
+; BOTH_REDIRECTED-NEXT: PARENT(stdout): Child exited with code 42
Index: llvm/test/lit.cfg.py
===================================================================
--- llvm/test/lit.cfg.py
+++ llvm/test/lit.cfg.py
@@ -149,7 +149,9 @@
     'llvm-rtdyld', 'llvm-size', 'llvm-split', 'llvm-strings', 'llvm-strip', 'llvm-tblgen',
     'llvm-c-test', 'llvm-cxxfilt', 'llvm-xray', 'yaml2obj', 'obj2yaml',
     'yaml-bench', 'verify-uselistorder',
-    'bugpoint', 'llc', 'llvm-symbolizer', 'opt', 'sancov', 'sanstats'])
+    'bugpoint', 'llc', 'llvm-symbolizer', 'opt', 'sancov', 'sanstats',
+    ToolSubst(r'\| \btrace\b', command=FindTool('trace'), verbatim=True, unresolved='fatal'),
+    ])
 
 # The following tools are optional
 tools.extend([
Index: llvm/utils/trace/CMakeLists.txt
===================================================================
--- /dev/null
+++ llvm/utils/trace/CMakeLists.txt
@@ -0,0 +1,7 @@
+set(LLVM_LINK_COMPONENTS
+  Support
+  )
+
+add_llvm_utility(trace
+  Trace.cpp
+  )
Index: llvm/utils/trace/Trace.cpp
===================================================================
--- /dev/null
+++ llvm/utils/trace/Trace.cpp
@@ -0,0 +1,170 @@
+//===- Trace.cpp - The 'trace' testing tool -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/LineIterator.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Program.h"
+
+#include <iostream>
+
+#include <io.h>
+
+using namespace llvm;
+
+static cl::opt<std::string> StdinFile("stdin", cl::desc("<stdin file>"),
+                                      cl::Optional);
+
+static cl::opt<std::string> StdoutFile("stdout", cl::desc("<stdout file>"),
+                                       cl::Optional);
+
+static cl::opt<std::string> StderrFile("stderr", cl::desc("<stderr file>"),
+                                       cl::Optional);
+
+static cl::list<std::string>
+    EnvVar("env", cl::desc("KEY:VALUE pair to set in target process"),
+           cl::Optional, cl::ZeroOrMore);
+
+static cl::opt<std::string>
+    Cwd("cwd", cl::desc("The current working directory of the process"),
+        cl::Optional);
+
+static cl::opt<std::string>
+    ExecFile("execfile", cl::desc("The command file to execute"), cl::Required);
+
+static cl::opt<bool> ExecNow("execnow", cl::ReallyHidden);
+
+static void handleWrite(StringRef Line) {
+  Line = Line.trim();
+
+  StringRef Dest;
+  StringRef Text;
+  std::tie(Dest, Text) = Line.split(' ');
+  int FD = -1;
+  if (Dest.equals_lower("stdout")) {
+    outs() << "CHILD(stdout): " << Text << "\n";
+    outs().flush();
+  } else if (Dest.equals_lower("stderr")) {
+    errs() << "CHILD(stderr): " << Text << "\n";
+    errs().flush();
+  } else if (to_integer(Dest, FD, 10)) {
+    raw_fd_ostream OS(FD, false, true);
+    OS << "CHILD(" << FD << "): " << Text << "\n";
+    OS.flush();
+  } else {
+    errs() << formatv(
+        "CHILD(stderr): Invalid argument '{0}' to command 'write'\n", Dest);
+    exit(-1);
+  }
+}
+
+static void handleRead(StringRef Line) {
+  Line = Line.trim();
+
+  StringRef Source;
+  StringRef LengthStr;
+
+  std::tie(Source, LengthStr) = Line.split(' ');
+
+  unsigned Length;
+  int FD = -1;
+  if (!to_integer(LengthStr, Length, 10)) {
+    errs() << formatv(
+        "CHILD(stderr): Invalid argument '{0}' to command 'read'\n", LengthStr);
+    exit(-1);
+  }
+
+  std::vector<char> InputBuffer;
+  InputBuffer.resize(Length);
+
+  if (Source.equals_lower("stdin"))
+    std::cin.get(InputBuffer.data(), Length);
+  else if (to_integer(Source, FD, 10)) {
+    ::read(FD, InputBuffer.data(), Length);
+  } else {
+    errs() << formatv(
+        "CHILD(stderr): Invalid argument '{0}' to command 'read'\n", Source);
+    exit(-1);
+  }
+  outs() << formatv("CHILD(stdout): Read {0} bytes from {1}: '{2}'\n", Length,
+                    Source, StringRef(InputBuffer.data(), InputBuffer.size()));
+}
+
+static void handleExit(StringRef Line) {
+  Line = Line.trim();
+
+  int Code;
+  if (!to_integer(Line, Code, 10)) {
+    errs() << formatv(
+        "CHILD(stderr): Invalid argument '{0}' to command 'exit'\n", Line);
+    exit(-1);
+  }
+
+  outs() << "CHILD(stdout): exiting with code " << Code << "\n";
+  outs().flush();
+  exit(Code);
+}
+
+static int run() {
+  auto FileContents = MemoryBuffer::getFile(ExecFile);
+  if (!FileContents) {
+    errs() << "CHILD(stderr): Unable to open execfile " << ExecFile << "\n";
+    return -1;
+  }
+  std::unique_ptr<MemoryBuffer> Buffer = std::move(*FileContents);
+  for (StringRef Line :
+       make_range(line_iterator(*Buffer, true, ';'), line_iterator())) {
+    Line = Line.trim();
+    if (Line.consume_front("write"))
+      handleWrite(Line);
+    else if (Line.consume_front("read"))
+      handleRead(Line);
+    else if (Line.consume_front("exit"))
+      handleExit(Line);
+    else {
+      errs() << "CHILD(stderr): Error in command: " << Line << "\n";
+      return -1;
+    }
+  }
+  outs() << "CHILD(stdout): EOF encountered, exiting\n";
+  return 0;
+}
+
+int main(int argc, char **argv) {
+  InitLLVM X(argc, argv);
+  cl::ParseCommandLineOptions(argc, argv);
+
+  if (ExecNow) {
+    outs() << "CHILD(stdout): Running\n";
+    outs().flush();
+    int ExitCode = run();
+    return ExitCode;
+  }
+
+  std::array<llvm::Optional<StringRef>, 3> Redirects;
+
+  if (StdinFile.getNumOccurrences() > 0)
+    Redirects[0] = StdinFile;
+  if (StdoutFile.getNumOccurrences() > 0)
+    Redirects[1] = StdoutFile;
+  if (StderrFile.getNumOccurrences() > 0)
+    Redirects[2] = StderrFile;
+
+  std::string Arg1 = formatv("-execfile={0}", ExecFile.getValue());
+  const char *Args[] = {argv[0], "-execnow", Arg1.c_str(), nullptr};
+
+  outs() << "PARENT(stdout): Running\n";
+  outs().flush();
+  int Result = sys::ExecuteAndWait(argv[0], Args, nullptr, Redirects);
+  outs() << "PARENT(stdout): Child exited with code " << Result << "\n";
+  outs().flush();
+  return 0;
+}