Index: include/llvm/Analysis/TargetTransformInfo.h
===================================================================
--- include/llvm/Analysis/TargetTransformInfo.h
+++ include/llvm/Analysis/TargetTransformInfo.h
@@ -165,6 +165,13 @@
   /// This overload allows specifying a set of candidate argument values.
   int getCallCost(const Function *F, ArrayRef<const Value *> Arguments) const;
 
+  /// \returns A value by which our inlining threshold should be multiplied, for
+  /// the given caller function.  This is primarily used to bump up the inlining
+  /// threshold wholesale on targets where calls are unusually expensive.
+  /// TODO: This is a rather blunt instrument.  Perhaps altering the costs of
+  /// individual classes of instructions would be better.
+  double getInliningThresholdMultiplier(const Function *Caller) const;
+
   /// \brief Estimate the cost of an intrinsic when lowered.
   ///
   /// Mirrors the \c getCallCost method but uses an intrinsic identifier.
@@ -586,6 +593,7 @@
   virtual int getCallCost(const Function *F, int NumArgs) = 0;
   virtual int getCallCost(const Function *F,
                           ArrayRef<const Value *> Arguments) = 0;
+  virtual double getInliningThresholdMultiplier(const Function *Caller) = 0;
   virtual int getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
                                ArrayRef<Type *> ParamTys) = 0;
   virtual int getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
@@ -705,6 +713,9 @@
                   ArrayRef<const Value *> Arguments) override {
     return Impl.getCallCost(F, Arguments);
   }
+  double getInliningThresholdMultiplier(const Function *Caller) override {
+    return Impl.getInliningThresholdMultiplier(Caller);
+  }
   int getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
                        ArrayRef<Type *> ParamTys) override {
     return Impl.getIntrinsicCost(IID, RetTy, ParamTys);
Index: include/llvm/Analysis/TargetTransformInfoImpl.h
===================================================================
--- include/llvm/Analysis/TargetTransformInfoImpl.h
+++ include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -128,6 +128,10 @@
     return TTI::TCC_Basic * (NumArgs + 1);
   }
 
+  double getInliningThresholdMultiplier(const Function * /* Caller */) {
+    return 1;
+  }
+
   unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
                             ArrayRef<Type *> ParamTys) {
     switch (IID) {
Index: include/llvm/CodeGen/BasicTTIImpl.h
===================================================================
--- include/llvm/CodeGen/BasicTTIImpl.h
+++ include/llvm/CodeGen/BasicTTIImpl.h
@@ -216,6 +216,10 @@
     return BaseT::getOperationCost(Opcode, Ty, OpTy);
   }
 
+  double getInliningThresholdMultiplier(const Function * /* Caller */) {
+    return 1;
+  }
+
   void getUnrollingPreferences(Loop *L, TTI::UnrollingPreferences &UP) {
     // This unrolling functionality is target independent, but to provide some
     // motivation for its intended use, for x86:
Index: lib/Analysis/InlineCost.cpp
===================================================================
--- lib/Analysis/InlineCost.cpp
+++ lib/Analysis/InlineCost.cpp
@@ -620,6 +620,11 @@
        ColdThreshold.getNumOccurrences() > 0) &&
       ColdCallee && ColdThreshold < Threshold)
     Threshold = ColdThreshold;
+
+  // Finally, take the target-specific inlining threshold multiplier into
+  // account.
+  Threshold =
+      std::round(Threshold * TTI.getInliningThresholdMultiplier(Caller));
 }
 
 bool CallAnalyzer::visitCmpInst(CmpInst &I) {
Index: lib/Analysis/TargetTransformInfo.cpp
===================================================================
--- lib/Analysis/TargetTransformInfo.cpp
+++ lib/Analysis/TargetTransformInfo.cpp
@@ -66,6 +66,14 @@
   return Cost;
 }
 
+double TargetTransformInfo::getInliningThresholdMultiplier(
+    const Function *Caller) const {
+  double Multiplier = TTIImpl->getInliningThresholdMultiplier(Caller);
+  assert(!std::isnan(Multiplier) && "Multiplier cannot be nan");
+  assert(!std::isinf(Multiplier) && "Multiplier cannot be infinity");
+  return Multiplier;
+}
+
 int TargetTransformInfo::getIntrinsicCost(
     Intrinsic::ID IID, Type *RetTy, ArrayRef<const Value *> Arguments) const {
   int Cost = TTIImpl->getIntrinsicCost(IID, RetTy, Arguments);