Index: include/llvm/Transforms/Instrumentation.h
===================================================================
--- include/llvm/Transforms/Instrumentation.h
+++ include/llvm/Transforms/Instrumentation.h
@@ -120,12 +120,17 @@
 
 // Options for EfficiencySanitizer sub-tools.
 struct EfficiencySanitizerOptions {
-  EfficiencySanitizerOptions() : ToolType(ESAN_None) {}
+  EfficiencySanitizerOptions()
+      : ToolType(ESAN_None), InstrumentFastpath(true),
+        InstrumentLoadsAndStores(true), InstrumentMemIntrinsics(true) {}
   enum Type {
     ESAN_None = 0,
     ESAN_CacheFrag,
     ESAN_WorkingSet,
   } ToolType;
+  bool InstrumentFastpath;
+  bool InstrumentLoadsAndStores;
+  bool InstrumentMemIntrinsics;
 };
 
 // Insert EfficiencySanitizer instrumentation.
Index: lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
+++ lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
@@ -56,6 +56,9 @@
 static cl::opt<bool> ClInstrumentMemIntrinsics(
     "esan-instrument-memintrinsics", cl::init(true),
     cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
+static cl::opt<bool> ClInstrumentFastpath(
+    "esan-instrument-fastpath", cl::init(true),
+    cl::desc("Instrument fastpath"), cl::Hidden);
 
 // Experiments show that the performance difference can be 2x or more,
 // and accuracy loss is typically negligible, so we turn this on by default.
@@ -121,6 +124,19 @@
   if (Options.ToolType == EfficiencySanitizerOptions::ESAN_None)
     Options.ToolType = EfficiencySanitizerOptions::ESAN_CacheFrag;
 
+  // Overwrite Options from the command line.
+  Options.InstrumentLoadsAndStores = ClInstrumentLoadsAndStores;
+  Options.InstrumentMemIntrinsics = ClInstrumentMemIntrinsics;
+  Options.InstrumentFastpath = ClInstrumentFastpath;
+
+  // Overwrite Options for tools.
+  // Disable load/store/intrinsics instrumentation if cfrag.
+  if (Options.ToolType == EfficiencySanitizerOptions::ESAN_CacheFrag) {
+    // FIXME: how do we run CacheFrag tool with loads/stores/meminstrinsics
+    // instrumentation?
+    Options.InstrumentLoadsAndStores = false;
+    Options.InstrumentMemIntrinsics = false;
+  }
   return Options;
 }
 
@@ -526,13 +542,13 @@
     }
   }
 
-  if (ClInstrumentLoadsAndStores) {
+  if (Options.InstrumentLoadsAndStores) {
     for (auto Inst : LoadsAndStores) {
       Res |= instrumentLoadOrStore(Inst, DL);
     }
   }
 
-  if (ClInstrumentMemIntrinsics) {
+  if (Options.InstrumentMemIntrinsics) {
     for (auto Inst : MemIntrinCalls) {
       Res |= instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
     }
@@ -591,7 +607,8 @@
                    {IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
                     ConstantInt::get(IntptrTy, TypeSizeBytes)});
   } else {
-    if (instrumentFastpath(I, DL, IsStore, Addr, Alignment)) {
+    if (Options.InstrumentFastpath &&
+        instrumentFastpath(I, DL, IsStore, Addr, Alignment)) {
       NumFastpaths++;
       return true;
     }
Index: test/Instrumentation/EfficiencySanitizer/struct_field_count_basic.ll
===================================================================
--- test/Instrumentation/EfficiencySanitizer/struct_field_count_basic.ll
+++ test/Instrumentation/EfficiencySanitizer/struct_field_count_basic.ll
@@ -1,6 +1,6 @@
 ; Test basic EfficiencySanitizer struct field count instrumentation.
 ;
-; RUN: opt < %s -esan -esan-cache-frag -esan-instrument-loads-and-stores=false -esan-instrument-memintrinsics=false -S | FileCheck %s
+; RUN: opt < %s -esan -esan-cache-frag -S | FileCheck %s
 
 %struct.A = type { i32, i32 }
 %union.U = type { double }
@@ -93,3 +93,11 @@
 ; CHECK-NEXT:   %k1 = load %struct.A*, %struct.A** %k, align 8
 ; CHECK-NEXT:   %arrayidx13 = getelementptr inbounds %struct.A, %struct.A* %k1, i64 0
 ; CHECK-NEXT:   ret i32 0
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+; Top-level:
+
+; CHECK: define internal void @esan.module_ctor()
+; CHECK: call void @__esan_init(i32 1, i8* bitcast ({ i8*, i32, { i8*, i32, i64*, i8** }* }* @21 to i8*))
+; CHECK: define internal void @esan.module_dtor()
+; CHECK: call void @__esan_exit(i8* bitcast ({ i8*, i32, { i8*, i32, i64*, i8** }* }* @21 to i8*))
Index: test/Instrumentation/EfficiencySanitizer/working_set_slow.ll
===================================================================
--- test/Instrumentation/EfficiencySanitizer/working_set_slow.ll
+++ test/Instrumentation/EfficiencySanitizer/working_set_slow.ll
@@ -1,6 +1,6 @@
-; Test basic EfficiencySanitizer cache frag instrumentation.
+; Test basic EfficiencySanitizer slowpath instrumentation.
 ;
-; RUN: opt < %s -esan -esan-cache-frag -S | FileCheck %s
+; RUN: opt < %s -esan -esan-working-set -esan-instrument-fastpath=false -S | FileCheck %s
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; Aligned loads:
@@ -254,6 +254,6 @@
 ; Top-level:
 
 ; CHECK: define internal void @esan.module_ctor()
-; CHECK: call void @__esan_init(i32 1, i8* bitcast ({ i8*, i32, { i8*, i32, i64*, i8** }* }* @1 to i8*))
+; CHECK: call void @__esan_init(i32 2, i8* null)
 ; CHECK: define internal void @esan.module_dtor()
-; CHECK: call void @__esan_exit(i8* bitcast ({ i8*, i32, { i8*, i32, i64*, i8** }* }* @1 to i8*))
+; CHECK: call void @__esan_exit(i8* null)