diff --git a/compiler-rt/lib/esan/esan_interface_internal.h b/compiler-rt/lib/esan/esan_interface_internal.h
@@ -0,0 +1,72 @@
+//===-- esan_interface_internal.h -------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of EfficiencySanitizer, a family of performance tuners.
+//
+// Calls to the functions declared in this header will be inserted by
+// the instrumentation module.
+//===----------------------------------------------------------------------===//
+
+#ifndef ESAN_INTERFACE_INTERNAL_H
+#define ESAN_INTERFACE_INTERNAL_H
+
+#include <sanitizer_common/sanitizer_internal_defs.h>
+
+// This header should NOT include any other headers.
+// All functions in this header are extern "C" and start with __esan_.
+
+extern "C" {
+
+// This should be kept consistent with LLVM's EfficiencySanitizerOptions.
+// The value is passed as a 32-bit integer by the compiler.
+typedef enum Type : u32 {
+  ESAN_None = 0,
+  ESAN_CacheFrag,
+} ToolType;
+
+// This function should be called at the very beginning of the process,
+// before any instrumented code is executed and before any call to malloc.
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_init(ToolType Tool);
+
+// The instrumentation module will insert a call to one of these routines prior
+// to each load and store instruction for which we do not have "fastpath"
+// inlined instrumentation.  These calls constitute the "slowpath" for our
+// tools.  We have separate routines for each type of memory access to enable
+// targeted optimization.
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_load1(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_load2(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_load4(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_load8(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_load16(void *Addr);
+
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_store1(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_store2(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_store4(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_store8(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_aligned_store16(void *Addr);
+
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_load2(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_load4(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_load8(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_load16(void *Addr);
+
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_store2(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_store4(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_store8(void *Addr);
+SANITIZER_INTERFACE_ATTRIBUTE void __esan_unaligned_store16(void *Addr);
+
+// These cover unusually-sized accesses.
+SANITIZER_INTERFACE_ATTRIBUTE
+void __esan_unaligned_loadN(void *Addr, uptr Size);
+SANITIZER_INTERFACE_ATTRIBUTE
+void __esan_unaligned_storeN(void *Addr, uptr Size);
+
+} // extern "C"
+
+#endif // ESAN_INTERFACE_INTERNAL_H
diff --git a/compiler-rt/test/CMakeLists.txt b/compiler-rt/test/CMakeLists.txt
@@ -70,6 +70,9 @@ if(COMPILER_RT_CAN_EXECUTE_TESTS)
   if(COMPILER_RT_HAS_SAFESTACK)
     add_subdirectory(safestack)
   endif()
+  if(COMPILER_RT_HAS_ESAN)
+    add_subdirectory(esan)
+  endif()
 endif()
 
 if(COMPILER_RT_STANDALONE_BUILD)

diff --git a/compiler-rt/test/esan/CMakeLists.txt b/compiler-rt/test/esan/CMakeLists.txt
@@ -0,0 +1,32 @@
+set(ESAN_TEST_DEPS ${SANITIZER_COMMON_LIT_TEST_DEPS})
+if(NOT COMPILER_RT_STANDALONE_BUILD)
+  list(APPEND ESAN_TEST_DEPS esan)
+endif()
+
+set(ESAN_TESTSUITES)
+
+set(ESAN_TEST_ARCH ${ESAN_SUPPORTED_ARCH})
+
+set(ESAN_LIT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
+
+foreach(arch ${ESAN_TEST_ARCH})
+  set(ESAN_TEST_TARGET_ARCH ${arch})
+  string(TOLOWER "-${arch}" ESAN_TEST_CONFIG_SUFFIX)
+  get_target_flags_for_arch(${arch} ESAN_TEST_TARGET_CFLAGS)
+  string(REPLACE ";" " " ESAN_TEST_TARGET_CFLAGS "${ESAN_TEST_TARGET_CFLAGS}")
+
+  string(TOUPPER ${arch} ARCH_UPPER_CASE)
+  set(CONFIG_NAME ${ARCH_UPPER_CASE}Config)
+
+  configure_lit_site_cfg(
+    ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
+    ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME}/lit.site.cfg)
+  list(APPEND ESAN_TESTSUITES ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME})
+endforeach()
+
+# TODO(bruening): add Unit/ tests as well
+
+add_lit_testsuite(check-esan "Running EfficiencySanitizer tests"
+  ${ESAN_TESTSUITES}
+  DEPENDS ${ESAN_TEST_DEPS})
+set_target_properties(check-esan PROPERTIES FOLDER "Esan tests")
diff --git a/compiler-rt/test/esan/TestCases/verbose-simple.c b/compiler-rt/test/esan/TestCases/verbose-simple.c
@@ -0,0 +1,11 @@
+// RUN: %clang_esan_frag -O0 %s -o %t 2>&1
+// RUN: %env_esan_opts=verbosity=1 %run %t 2>&1 | FileCheck %s
+
+#include <stdlib.h>
+#include <string.h>
+int main(int argc, char **argv) {
+  // CHECK:      in esan::initializeLibrary
+  // CHECK-NEXT: in esan::finalizeLibrary
+  // CHECK-NEXT: {{.*}}EfficiencySanitizer is not finished: nothing yet to report
+  return 0;
+}
diff --git a/compiler-rt/test/esan/lit.cfg b/compiler-rt/test/esan/lit.cfg
@@ -0,0 +1,32 @@
+# -*- Python -*-
+
+import os
+
+# Setup config name.
+config.name = 'EfficiencySanitizer' + config.name_suffix
+
+# Setup source root.
+config.test_source_root = os.path.dirname(__file__)
+
+# Setup default compiler flags used with -fsanitize=efficiency option.
+base_cflags = ([config.target_cflags] + config.debug_info_flags)
+base_cxxflags = config.cxx_mode_flags + base_cflags
+
+frag_cflags = (["-fsanitize=efficiency-cache-frag"] + base_cflags)
+
+def build_invocation(compile_flags):
+  return " " + " ".join([config.clang] + compile_flags) + " "
+
+config.substitutions.append( ("%clang_esan_frag ",
+                              build_invocation(frag_cflags)) )
+
+default_esan_opts = ''
+config.substitutions.append(('%env_esan_opts=',
+                             'env ESAN_OPTIONS=' + default_esan_opts))
+
+# Default test suffixes.
+config.suffixes = ['.c', '.cpp']
+
+# EfficiencySanitizer tests are currently supported on Linux x86-64 only.
+if config.host_os not in ['Linux'] or config.target_arch != 'x86_64':
+  config.unsupported = True
diff --git a/compiler-rt/test/esan/lit.site.cfg.in b/compiler-rt/test/esan/lit.site.cfg.in
@@ -0,0 +1,14 @@
+## Autogenerated by LLVM/Clang configuration.
+# Do not edit!
+
+# Tool-specific config options.
+config.name_suffix = "@ESAN_TEST_CONFIG_SUFFIX@"
+config.esan_lit_source_dir = "@ESAN_LIT_SOURCE_DIR@"
+config.target_cflags = "@ESAN_TEST_TARGET_CFLAGS@"
+config.target_arch = "@ESAN_TEST_TARGET_ARCH@"
+
+# Load common config for all compiler-rt lit tests.
+lit_config.load_config(config, "@COMPILER_RT_BINARY_DIR@/test/lit.common.configured")
+
+# Load tool-specific config that would do the real work.
+lit_config.load_config(config, "@ESAN_LIT_SOURCE_DIR@/lit.cfg")