Index: include/llvm/Analysis/TargetTransformInfo.h
===================================================================
--- include/llvm/Analysis/TargetTransformInfo.h
+++ include/llvm/Analysis/TargetTransformInfo.h
@@ -326,6 +326,11 @@
   /// by referencing its sub-register AX.
   bool isTruncateFree(Type *Ty1, Type *Ty2) const;
 
+  /// \brief Return true if it's free to zero extend a value of type Ty1 to type
+  /// Ty2. e.g. on x86-64, all instructions that define 32-bit values implicit
+  /// zero-extend the result out to 64 bits.
+  bool isZExtFree(Type *Ty1, Type *Ty2) const;
+
   /// \brief Return true if it is profitable to hoist instruction in the
   /// then/else to before if.
   bool isProfitableToHoist(Instruction *I) const;
@@ -546,6 +551,7 @@
                                    int64_t BaseOffset, bool HasBaseReg,
                                    int64_t Scale) = 0;
   virtual bool isTruncateFree(Type *Ty1, Type *Ty2) = 0;
+  virtual bool isZExtFree(Type *Ty1, Type *Ty2) = 0;
   virtual bool isProfitableToHoist(Instruction *I) = 0;
   virtual bool isTypeLegal(Type *Ty) = 0;
   virtual unsigned getJumpBufAlignment() = 0;
@@ -665,6 +671,9 @@
   bool isTruncateFree(Type *Ty1, Type *Ty2) override {
     return Impl.isTruncateFree(Ty1, Ty2);
   }
+  bool isZExtFree(Type *Ty1, Type *Ty2) override {
+    return Impl.isZExtFree(Ty1, Ty2);
+  }
   bool isProfitableToHoist(Instruction *I) override {
     return Impl.isProfitableToHoist(I);
   }
Index: include/llvm/Analysis/TargetTransformInfoImpl.h
===================================================================
--- include/llvm/Analysis/TargetTransformInfoImpl.h
+++ include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -227,6 +227,8 @@
 
   bool isTruncateFree(Type *Ty1, Type *Ty2) { return false; }
 
+  bool isZExtFree(Type *Ty1, Type *Ty2) { return false; }
+
   bool isProfitableToHoist(Instruction *I) { return true; }
 
   bool isTypeLegal(Type *Ty) { return false; }
Index: include/llvm/CodeGen/BasicTTIImpl.h
===================================================================
--- include/llvm/CodeGen/BasicTTIImpl.h
+++ include/llvm/CodeGen/BasicTTIImpl.h
@@ -148,6 +148,10 @@
     return getTLI()->isTruncateFree(Ty1, Ty2);
   }
 
+  bool isZExtFree(Type *Ty1, Type *Ty2) const {
+    return getTLI()->isZExtFree(Ty1, Ty2);
+  }
+
   bool isProfitableToHoist(Instruction *I) {
     return getTLI()->isProfitableToHoist(I);
   }
Index: lib/Analysis/TargetTransformInfo.cpp
===================================================================
--- lib/Analysis/TargetTransformInfo.cpp
+++ lib/Analysis/TargetTransformInfo.cpp
@@ -127,6 +127,10 @@
   return TTIImpl->isTruncateFree(Ty1, Ty2);
 }
 
+bool TargetTransformInfo::isZExtFree(Type *Ty1, Type *Ty2) const {
+  return TTIImpl->isZExtFree(Ty1, Ty2);
+}
+
 bool TargetTransformInfo::isProfitableToHoist(Instruction *I) const {
   return TTIImpl->isProfitableToHoist(I);
 }