2 files changed, 19 insertions, 6 deletions
diff --git a/llvm/include/llvm/CodeGen/Passes.h b/llvm/include/llvm/CodeGen/Passes.h
index 26fb834d95a..09e66098748 100644
--- a/llvm/include/llvm/CodeGen/Passes.h
+++ b/llvm/include/llvm/CodeGen/Passes.h
@@ -53,7 +53,11 @@ namespace llvm {
   /// using the MIR serialization format.
   MachineFunctionPass *createPrintMIRPass(raw_ostream &OS);
 
-  MachineFunctionPass *createResetMachineFunctionPass();
+  /// This pass resets a MachineFunction when it has the FailedISel property
+  /// as if it was just created.
+  /// If EmitFallbackDiag is true, the pass will emit a
+  /// DiagnosticInfoISelFallback for every MachineFunction it resets.
+  MachineFunctionPass *createResetMachineFunctionPass(bool EmitFallbackDiag);
 
   /// createCodeGenPreparePass - Transform the code to expose more pattern
   /// matching during instruction selection.
diff --git a/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp b/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp
index 3b7729a0540..07a8259a70c 100644
--- a/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp
+++ b/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp
@@ -13,6 +13,7 @@
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;
 
@@ -20,11 +21,14 @@ using namespace llvm;
 
 namespace {
   class ResetMachineFunction : public MachineFunctionPass {
+    /// Tells whether or not this pass should emit a fallback
+    /// diagnostic when it resets a function.
+    bool EmitFallbackDiag;
+
   public:
     static char ID; // Pass identification, replacement for typeid
-    ResetMachineFunction() :
-      MachineFunctionPass(ID) {
-    }
+    ResetMachineFunction(bool EmitFallbackDiag = false)
+        : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag) {}
 
     const char *getPassName() const override {
       return "ResetMachineFunction";
@@ -35,6 +39,11 @@ namespace {
               MachineFunctionProperties::Property::FailedISel)) {
         DEBUG(dbgs() << "Reseting: " << MF.getName() << '\n');
         MF.reset();
+        if (EmitFallbackDiag) {
+          const Function &F = *MF.getFunction();
+          DiagnosticInfoISelFallback DiagFallback(F);
+          F.getContext().diagnose(DiagFallback);
+        }
         return true;
       }
       return false;
@@ -48,6 +57,6 @@ INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
                 "reset machine function if ISel failed", false, false)
 
 MachineFunctionPass *
-llvm::createResetMachineFunctionPass() {
-  return new ResetMachineFunction();
+llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false) {
+  return new ResetMachineFunction(EmitFallbackDiag);
 }