Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -637,12 +637,25 @@
 def fprofile_sample_use_EQ : Joined<["-"], "fprofile-sample-use=">,
     Group<f_Group>, Flags<[DriverOption, CC1Option]>,
     HelpText<"Enable sample-based profile guided optimizations">;
+def fprofile_sample_accurate : Flag<["-"], "fprofile-sample-accurate">,
+    Group<f_Group>, Flags<[DriverOption, CC1Option]>,
+    HelpText<"Specifies that the sample profile is accurate">,
+    DocBrief<[{Specifies that the sample profile is accurate. If the sample
+               profile is accurate, callsites without profile samples are marked
+               as cold. Otherwise, treat callsites without profile samples as if
+               we have no profile}]>;
+def fno_profile_sample_accurate : Flag<["-"], "fno-profile-sample-accurate">,
+  Group<f_Group>, Flags<[DriverOption]>;
 def fauto_profile : Flag<["-"], "fauto-profile">, Group<f_Group>,
     Alias<fprofile_sample_use>;
 def fno_auto_profile : Flag<["-"], "fno-auto-profile">, Group<f_Group>,
     Alias<fno_profile_sample_use>;
 def fauto_profile_EQ : Joined<["-"], "fauto-profile=">,
     Alias<fprofile_sample_use_EQ>;
+def fauto_profile_accurate : Flag<["-"], "fauto-profile-accurate">,
+    Group<f_Group>, Alias<fprofile_sample_accurate>;
+def fno_auto_profile_accurate : Flag<["-"], "fno-auto-profile-accurate">,
+    Group<f_Group>, Alias<fno_profile_sample_accurate>;
 def fdebug_info_for_profiling : Flag<["-"], "fdebug-info-for-profiling">, Group<f_Group>,
     Flags<[CC1Option]>,
     HelpText<"Emit extra debug info to make sample profile more accurate.">;
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -183,6 +183,7 @@
 CODEGENOPT(UnwindTables      , 1, 0) ///< Emit unwind tables.
 CODEGENOPT(VectorizeLoop     , 1, 0) ///< Run loop vectorizer.
 CODEGENOPT(VectorizeSLP      , 1, 0) ///< Run SLP vectorizer.
+CODEGENOPT(ProfileSampleAccurate, 1, 0) ///< Sample profile is accurate.
 
   /// Attempt to use register sized accesses to bit-fields in structures, when
   /// possible.
Index: lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- lib/CodeGen/CodeGenFunction.cpp
+++ lib/CodeGen/CodeGenFunction.cpp
@@ -837,6 +837,10 @@
   Fn->addFnAttr("no-jump-tables",
                 llvm::toStringRef(CGM.getCodeGenOpts().NoUseJumpTables));
 
+  // Add profile-sample-accurate value.
+  if (CGM.getCodeGenOpts().ProfileSampleAccurate)
+    Fn->addFnAttr("profile-sample-accurate");
+
   if (getLangOpts().OpenCL) {
     // Add metadata for a kernel function.
     if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -2340,6 +2340,10 @@
                     true))
     CmdArgs.push_back("-fno-jump-tables");
 
+  if (Args.hasFlag(options::OPT_fprofile_sample_accurate,
+                   options::OPT_fno_profile_sample_accurate, false))
+    CmdArgs.push_back("-fprofile-sample-accurate");
+
   if (!Args.hasFlag(options::OPT_fpreserve_as_comments,
                     options::OPT_fno_preserve_as_comments, true))
     CmdArgs.push_back("-fno-preserve-as-comments");
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -652,6 +652,8 @@
 
   Opts.NoUseJumpTables = Args.hasArg(OPT_fno_jump_tables);
 
+  Opts.ProfileSampleAccurate = Args.hasArg(OPT_fprofile_sample_accurate);
+
   Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
   Opts.EmitSummaryIndex = false;
   if (Arg *A = Args.getLastArg(OPT_flto_EQ)) {
Index: test/CodeGen/profile-sample-accurate.c
===================================================================
--- /dev/null
+++ test/CodeGen/profile-sample-accurate.c
@@ -0,0 +1,7 @@
+// Test to ensure -emit-llvm profile-sample-accurate is honored by clang.
+// RUN: %clang -S -emit-llvm %s -fprofile-sample-accurate -o - | FileCheck %s
+
+// CHECK: define void @foo()
+// CHECK: attributes {{.*}} "profile-sample-accurate"
+void foo() {
+}
Index: test/Driver/clang_f_opts.c
===================================================================
--- test/Driver/clang_f_opts.c
+++ test/Driver/clang_f_opts.c
@@ -53,6 +53,9 @@
 // CHECK-REROLL-LOOPS: "-freroll-loops"
 // CHECK-NO-REROLL-LOOPS-NOT: "-freroll-loops"
 
+// RUN: %clang -### -S -fprofile-sample-accurate %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-SAMPLE-ACCURATE %s
+// CHECK-PROFILE-SAMPLE-ACCURATE: "-fprofile-sample-accurate"
+
 // RUN: %clang -### -S -fprofile-sample-use=%S/Inputs/file.prof %s 2>&1 | FileCheck -check-prefix=CHECK-SAMPLE-PROFILE %s
 // CHECK-SAMPLE-PROFILE: "-fprofile-sample-use={{.*}}/file.prof"
 
Index: test/Integration/thinlto_profile_sample_accurate.c
===================================================================
--- /dev/null
+++ test/Integration/thinlto_profile_sample_accurate.c
@@ -0,0 +1,9 @@
+// Test to ensure -emit-llvm profile-sample-accurate is honored in ThinLTO.
+// RUN: %clang -O2 %s -flto=thin -fprofile-sample-accurate -c -o %t.o
+// RUN: llvm-lto -thinlto -o %t %t.o
+// RUN: %clang_cc1 -O2 -x ir %t.o -fthinlto-index=%t.thinlto.bc -emit-llvm -o - | FileCheck %s
+
+// CHECK: define void @foo()
+// CHECK: attributes {{.*}} "profile-sample-accurate"
+void foo() {
+}