Index: lib/Transforms/IPO/WholeProgramDevirt.cpp
===================================================================
--- lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -35,6 +35,7 @@
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
@@ -215,7 +216,15 @@
   // of that field for details.
   unsigned *NumUnsafeUses;
 
+  void emitRemark() {
+    Function *F = CS.getCaller();
+    emitOptimizationRemark(F->getContext(), DEBUG_TYPE, *F,
+                           CS.getInstruction()->getDebugLoc(),
+                           "devirtualized call");
+  }
+
   void replaceAndErase(Value *New) {
+    emitRemark();
     CS->replaceAllUsesWith(New);
     if (auto II = dyn_cast<InvokeInst>(CS.getInstruction())) {
       BranchInst::Create(II->getNormalDest(), CS.getInstruction());
@@ -394,6 +403,7 @@
 
   // If so, update each call site to call that implementation directly.
   for (auto &&VCallSite : CallSites) {
+    VCallSite.emitRemark();
     VCallSite.CS.setCalledFunction(ConstantExpr::getBitCast(
         TheFn, VCallSite.CS.getCalledValue()->getType()));
     // This use is no longer unsafe.
Index: test/Transforms/WholeProgramDevirt/devirt-single-impl-check.ll
===================================================================
--- test/Transforms/WholeProgramDevirt/devirt-single-impl-check.ll
+++ test/Transforms/WholeProgramDevirt/devirt-single-impl-check.ll
@@ -1,8 +1,11 @@
-; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+; RUN: opt -S -wholeprogramdevirt -pass-remarks=wholeprogramdevirt %s 2>&1 | FileCheck %s
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
+; CHECK: remark: <unknown>:0:0: devirtualized call
+; CHECK-NOT: devirtualized call
+
 @vt1 = constant [1 x i8*] [i8* bitcast (void (i8*)* @vf to i8*)], !type !0
 @vt2 = constant [1 x i8*] [i8* bitcast (void (i8*)* @vf to i8*)], !type !0
 
Index: test/Transforms/WholeProgramDevirt/non-constant-vtable.ll
===================================================================
--- test/Transforms/WholeProgramDevirt/non-constant-vtable.ll
+++ test/Transforms/WholeProgramDevirt/non-constant-vtable.ll
@@ -1,4 +1,6 @@
-; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+; RUN: opt -S -wholeprogramdevirt -pass-remarks=wholeprogramdevirt %s 2>&1 | FileCheck %s
+
+; CHECK-NOT: devirtualized call
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
Index: test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
===================================================================
--- test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
+++ test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
@@ -1,8 +1,13 @@
-; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+; RUN: opt -S -wholeprogramdevirt -pass-remarks=wholeprogramdevirt %s 2>&1 | FileCheck %s
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
+; CHECK: remark: <unknown>:0:0: devirtualized call
+; CHECK: remark: <unknown>:0:0: devirtualized call
+; CHECK: remark: <unknown>:0:0: devirtualized call
+; CHECK-NOT: devirtualized call
+
 ; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\01\01\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf1i32 to i8*)], [0 x i8] zeroinitializer }, section "vt1sec", !type [[T8:![0-9]+]]
 @vt1 = constant [3 x i8*] [
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),