Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -318,8 +318,13 @@
                                      !CodeGenOpts.DisableLifetimeMarkers);
     PMBuilder.Inliner = createAlwaysInlinerLegacyPass(InsertLifetimeIntrinsics);
   } else {
+    // We do not want to inline hot callsites for SamplePGO module-summary build
+    // because profile annotation will happen again in ThinLTO backend, and we
+    // want the IR of the hot path to match the profile.
     PMBuilder.Inliner = createFunctionInliningPass(
-        CodeGenOpts.OptimizationLevel, CodeGenOpts.OptimizeSize);
+        CodeGenOpts.OptimizationLevel, CodeGenOpts.OptimizeSize,
+        (!CodeGenOpts.SampleProfileFile.empty() &&
+         CodeGenOpts.EmitSummaryIndex));
   }
 
   PMBuilder.OptLevel = CodeGenOpts.OptimizationLevel;
Index: test/CodeGen/Inputs/pgo-sample-thinlto-summary.prof
===================================================================
--- /dev/null
+++ test/CodeGen/Inputs/pgo-sample-thinlto-summary.prof
@@ -0,0 +1,2 @@
+bar:100:100
+ 2: 2000 foo:2000
Index: test/CodeGen/pgo-sample-thinlto-summary.c
===================================================================
--- /dev/null
+++ test/CodeGen/pgo-sample-thinlto-summary.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=INLINE
+// RUN: %clang_cc1 -O2 -fprofile-sample-use=%S/Inputs/pgo-sample-thinlto-summary.prof %s -emit-llvm -flto=thin -o - 2>&1 | FileCheck %s -check-prefix=NOINLINE
+// Checks if hot call is inlined by normal compile, but not inlined by
+// thinlto compile.
+
+int baz(int);
+int g;
+
+void foo(int n) {
+  for (int i = 0; i < n; i++)
+    g += baz(i);
+}
+
+// INLINE-NOT: call{{.*}}foo
+// NOINLINE: call{{.*}}foo
+void bar(int n) {
+  for (int i = 0; i < n; i++)
+    foo(i);
+}