Index: include/clang/Basic/Sanitizers.def
===================================================================
--- include/clang/Basic/Sanitizers.def
+++ include/clang/Basic/Sanitizers.def
@@ -116,8 +116,10 @@
 
 // EfficiencySanitizer
 SANITIZER("efficiency-cache-frag", EfficiencyCacheFrag)
+SANITIZER("efficiency-working-set", EfficiencyWorkingSet)
 // Meta-group only used internally.
-SANITIZER_GROUP("efficiency-all", Efficiency, EfficiencyCacheFrag)
+SANITIZER_GROUP("efficiency-all", Efficiency,
+                EfficiencyCacheFrag | EfficiencyWorkingSet)
 
 // Magic group, containing all sanitizers. For example, "-fno-sanitize=all"
 // can be used to disable all the sanitizers.
Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -258,6 +258,8 @@
   EfficiencySanitizerOptions Opts;
   if (LangOpts.Sanitize.has(SanitizerKind::EfficiencyCacheFrag))
     Opts.ToolType = EfficiencySanitizerOptions::ESAN_CacheFrag;
+  else if (LangOpts.Sanitize.has(SanitizerKind::EfficiencyWorkingSet))
+    Opts.ToolType = EfficiencySanitizerOptions::ESAN_WorkingSet;
   PM.add(createEfficiencySanitizerPass(Opts));
 }
 
Index: test/Driver/esan.c
===================================================================
--- test/Driver/esan.c
+++ test/Driver/esan.c
@@ -2,8 +2,11 @@
 // RUN: %clang -O1 -target x86_64-unknown-linux -fsanitize=efficiency-cache-frag %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang -O2 -target x86_64-unknown-linux -fsanitize=efficiency-cache-frag %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang -O3 -target x86_64-unknown-linux -fsanitize=efficiency-cache-frag %s -S -emit-llvm -o - | FileCheck %s
-// RUN: %clang     -target x86_64-unknown-linux -fsanitize=efficiency-cache-frag  %s -S -emit-llvm -o - | FileCheck %s
-// Verify that -fsanitize=efficiency-cache-frag invokes esan instrumentation.
+// RUN: %clang     -target x86_64-unknown-linux -fsanitize=efficiency-working-set %s -S -emit-llvm -o - | FileCheck %s
+// RUN: %clang -O1 -target x86_64-unknown-linux -fsanitize=efficiency-working-set %s -S -emit-llvm -o - | FileCheck %s
+// RUN: %clang -O2 -target x86_64-unknown-linux -fsanitize=efficiency-working-set %s -S -emit-llvm -o - | FileCheck %s
+// RUN: %clang -O3 -target x86_64-unknown-linux -fsanitize=efficiency-working-set %s -S -emit-llvm -o - | FileCheck %s
+// Verify that -fsanitize=efficiency-* invokes esan instrumentation.
 
 int foo(int *a) { return *a; }
 // CHECK: __esan_init
Index: test/Driver/fsanitize.c
===================================================================
--- test/Driver/fsanitize.c
+++ test/Driver/fsanitize.c
@@ -84,19 +84,24 @@
 // CHECK-SANKA-SANL: '-fsanitize=kernel-address' not allowed with '-fsanitize=leak'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-cache-frag,address -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANA
-// CHECK-SANE-SANA: '-fsanitize=efficiency-cache-frag' not allowed with '-fsanitize=address'
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-working-set,address -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANA
+// CHECK-SANE-SANA: '-fsanitize=efficiency-{{.*}}' not allowed with '-fsanitize=address'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-cache-frag,leak -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANL
-// CHECK-SANE-SANL: '-fsanitize=efficiency-cache-frag' not allowed with '-fsanitize=leak'
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-working-set,leak -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANL
+// CHECK-SANE-SANL: '-fsanitize=efficiency-{{.*}}' not allowed with '-fsanitize=leak'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-cache-frag,thread -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANT
-// CHECK-SANE-SANT: '-fsanitize=efficiency-cache-frag' not allowed with '-fsanitize=thread'
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-working-set,thread -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANT
+// CHECK-SANE-SANT: '-fsanitize=efficiency-{{.*}}' not allowed with '-fsanitize=thread'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-cache-frag,memory -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANM
-// CHECK-SANE-SANM: '-fsanitize=efficiency-cache-frag' not allowed with '-fsanitize=memory'
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-working-set,memory -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANM
+// CHECK-SANE-SANM: '-fsanitize=efficiency-{{.*}}' not allowed with '-fsanitize=memory'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-cache-frag,kernel-address -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANKA
-// CHECK-SANE-SANKA: '-fsanitize=efficiency-cache-frag' not allowed with '-fsanitize=kernel-address'
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-working-set,kernel-address -pie -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-SANE-SANKA
+// CHECK-SANE-SANKA: '-fsanitize=efficiency-{{.*}}' not allowed with '-fsanitize=kernel-address'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ONLY-TRACK-ORIGINS
 // CHECK-ONLY-TRACK-ORIGINS: warning: argument unused during compilation: '-fsanitize-memory-track-origins'
@@ -272,22 +277,28 @@
 // CHECK-ASAN-OPENBSD: unsupported option '-fsanitize=address' for target 'i386-pc-openbsd'
 
 // RUN: %clang -target i686-linux-gnu -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-X86
-// CHECK-ESAN-X86: error: unsupported option '-fsanitize=efficiency-cache-frag' for target 'i686--linux-gnu'
+// RUN: %clang -target i686-linux-gnu -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-X86
+// CHECK-ESAN-X86: error: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'i686--linux-gnu'
 
 // RUN: %clang -target x86_64-apple-darwin10 -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-DARWIN
-// CHECK-ESAN-DARWIN: unsupported option '-fsanitize=efficiency-cache-frag' for target 'x86_64-apple-darwin10'
+// RUN: %clang -target x86_64-apple-darwin10 -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-DARWIN
+// CHECK-ESAN-DARWIN: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'x86_64-apple-darwin10'
 
 // RUN: %clang -target i386-apple-darwin -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-I386-DARWIN
-// CHECK-ESAN-I386-DARWIN: unsupported option '-fsanitize=efficiency-cache-frag' for target 'i386-apple-darwin'
+// RUN: %clang -target i386-apple-darwin -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-I386-DARWIN
+// CHECK-ESAN-I386-DARWIN: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'i386-apple-darwin'
 
 // RUN: %clang -target arm-apple-ios -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-ARM-IOS
-// CHECK-ESAN-ARM-IOS: unsupported option '-fsanitize=efficiency-cache-frag' for target 'arm-apple-ios'
+// RUN: %clang -target arm-apple-ios -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-ARM-IOS
+// CHECK-ESAN-ARM-IOS: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'arm-apple-ios'
 
 // RUN: %clang -target i386-apple-iossimulator -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-I386-IOSSIMULATOR
-// CHECK-ESAN-I386-IOSSIMULATOR: unsupported option '-fsanitize=efficiency-cache-frag' for target 'i386-apple-iossimulator'
+// RUN: %clang -target i386-apple-iossimulator -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-I386-IOSSIMULATOR
+// CHECK-ESAN-I386-IOSSIMULATOR: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'i386-apple-iossimulator'
 
 // RUN: %clang -target i386-apple-tvossimulator -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-I386-TVOSSIMULATOR
-// CHECK-ESAN-I386-TVOSSIMULATOR: unsupported option '-fsanitize=efficiency-cache-frag' for target 'i386-apple-tvossimulator'
+// RUN: %clang -target i386-apple-tvossimulator -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-I386-TVOSSIMULATOR
+// CHECK-ESAN-I386-TVOSSIMULATOR: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'i386-apple-tvossimulator'
 
 
 
@@ -397,7 +408,8 @@
 // RUN: %clang -target x86_64-scei-ps4 -fsanitize=thread %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TSAN-PS4
 // CHECK-TSAN-PS4: unsupported option '-fsanitize=thread' for target 'x86_64-scei-ps4'
 // RUN: %clang -target x86_64-scei-ps4 -fsanitize=efficiency-cache-frag %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-PS4
-// CHECK-ESAN-PS4: unsupported option '-fsanitize=efficiency-cache-frag' for target 'x86_64-scei-ps4'
+// RUN: %clang -target x86_64-scei-ps4 -fsanitize=efficiency-working-set %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ESAN-PS4
+// CHECK-ESAN-PS4: unsupported option '-fsanitize=efficiency-{{.*}}' for target 'x86_64-scei-ps4'
 // RUN: %clang -target x86_64-scei-ps4 -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-PS4
 // Make sure there are no *.{o,bc} or -l passed before the ASan library.
 // CHECK-ASAN-PS4-NOT: {{(\.(o|bc)"? |-l).*-lSceDbgAddressSanitizer_stub_weak}}
Index: test/Driver/sanitize_unwind_tables.c
===================================================================
--- test/Driver/sanitize_unwind_tables.c
+++ test/Driver/sanitize_unwind_tables.c
@@ -8,5 +8,6 @@
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=thread %s -### 2>&1 |  FileCheck %s
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=dataflow %s -### 2>&1 |  FileCheck %s
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-cache-frag %s -### 2>&1 |  FileCheck %s
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=efficiency-working-set %s -### 2>&1 |  FileCheck %s
 
 // CHECK: -munwind-tables
Index: test/Driver/sanitizer-ld.c
===================================================================
--- test/Driver/sanitizer-ld.c
+++ test/Driver/sanitizer-ld.c
@@ -428,6 +428,9 @@
 // RUN: %clang -fsanitize=efficiency-cache-frag %s -### -o %t.o 2>&1 \
 // RUN:     -target x86_64-unknown-linux \
 // RUN:   | FileCheck --check-prefix=CHECK-ESAN-LINUX %s
+// RUN: %clang -fsanitize=efficiency-working-set %s -### -o %t.o 2>&1 \
+// RUN:     -target x86_64-unknown-linux \
+// RUN:   | FileCheck --check-prefix=CHECK-ESAN-LINUX %s
 //
 // CHECK-ESAN-LINUX: "{{(.*[^-.0-9A-Z_a-z])?}}ld{{(.exe)?}}"
 // CHECK-ESAN-LINUX: libclang_rt.esan-x86_64.a
Index: test/Lexer/has_feature_efficiency_sanitizer.cpp
===================================================================
--- test/Lexer/has_feature_efficiency_sanitizer.cpp
+++ test/Lexer/has_feature_efficiency_sanitizer.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -E -fsanitize=efficiency-cache-frag %s -o - | FileCheck --check-prefix=CHECK-ESAN %s
+// RUN: %clang_cc1 -E -fsanitize=efficiency-working-set %s -o - | FileCheck --check-prefix=CHECK-ESAN %s
 // RUN: %clang_cc1 -E  %s -o - | FileCheck --check-prefix=CHECK-NO-ESAN %s
 
 #if __has_feature(efficiency_sanitizer)