Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -357,6 +357,10 @@
           "static data member of %2|"
           "field of %2}1">,
   InGroup<Shadow>, DefaultIgnore;
+  
+def error_inoutput_conflict_with_clobber : Error<
+  "asm-specifier for input or output variable conflicts with asm" 
+  " clobber list">;
 
 // C++ using declarations
 def err_using_requires_qualname : Error<
Index: lib/Sema/SemaStmtAsm.cpp
===================================================================
--- lib/Sema/SemaStmtAsm.cpp
+++ lib/Sema/SemaStmtAsm.cpp
@@ -164,6 +164,9 @@
     return NS;
   }
 
+  std::vector<std::pair<StringRef, clang::SourceLocation> > InputVars;
+  std::vector<std::pair<StringRef, clang::SourceLocation> > OutputVars;
+  
   for (unsigned i = 0; i != NumOutputs; i++) {
     StringLiteral *Literal = Constraints[i];
     assert(Literal->isAscii());
@@ -201,6 +204,26 @@
     if (OutputExpr->isTypeDependent())
       continue;
 
+    // Add the output's register and location in the command line in order to
+    // check for conflicts with the clobber list
+    if (const DeclRefExpr *AsmDeclRef = dyn_cast<DeclRefExpr>(OutputExpr)){
+      // Handle cases where the output expression is a variable
+      const VarDecl *Variable = dyn_cast<VarDecl>(AsmDeclRef->getDecl());
+      if (Variable && Variable->getStorageClass() == SC_Register){
+        AsmLabelAttr *Attr = Variable->getAttr<AsmLabelAttr>();
+        if (Attr){
+          OutputVars.push_back(std::pair<StringRef, SourceLocation>(
+            // Mapping the actual register with the appropriate variable in the asm output variables list
+            Attr->getLabel(), OutputExpr->getSourceRange().getBegin()));
+        }
+      }
+    } else if (const StringLiteral *AsmStringLit =
+                     dyn_cast<StringLiteral>(OutputExpr)) {
+      // Handle cases where the output expression is a explicit register
+      OutputVars.push_back(std::pair<StringRef, SourceLocation>(
+        AsmStringLit->getString(), OutputExpr->getSourceRange().getBegin()));
+    }
+
     Expr::isModifiableLvalueResult IsLV =
         OutputExpr->isModifiableLvalue(Context, /*Loc=*/nullptr);
     switch (IsLV) {
@@ -304,6 +327,26 @@
       Exprs[i] = Result.get();
     }
 
+    // Add the input's register and location in the command line in order to
+    // check for conflicts with the clobber list
+    if (const DeclRefExpr *AsmDeclRef = dyn_cast<DeclRefExpr>(InputExpr)){
+      // Handle cases where the input expression is a variable
+      const VarDecl *Variable = dyn_cast<VarDecl>(AsmDeclRef->getDecl());
+      if (Variable && Variable->getStorageClass() == SC_Register){
+        AsmLabelAttr *Attr = Variable->getAttr<AsmLabelAttr>();
+        if (Attr){
+          InputVars.push_back(std::pair<StringRef, SourceLocation>(
+            // Mapping the actual register with the appropriate variable in the asm input variables list
+            Attr->getLabel(), InputExpr->getSourceRange().getBegin()));
+        }
+      }
+    } else if (const StringLiteral *AsmStringLit =
+                     dyn_cast<StringLiteral>(InputExpr)) {
+      // Handle cases where the output expression is a explicit register
+      InputVars.push_back(std::pair<StringRef, SourceLocation>(
+        AsmStringLit->getString(), InputExpr->getSourceRange().getBegin()));
+    }
+
     if (Info.allowsRegister()) {
       if (InputExpr->getType()->isVoidType()) {
         return StmtError(Diag(InputExpr->getLocStart(),
@@ -342,6 +385,18 @@
     if (!Context.getTargetInfo().isValidClobber(Clobber))
       return StmtError(Diag(Literal->getLocStart(),
                   diag::err_asm_unknown_register_name) << Clobber);
+    // Check if same register appears in both output list and clobber list
+    for (auto it = OutputVars.begin(); it != OutputVars.end(); ++it) {
+      if (Clobber == it->first)
+        return StmtError(
+          Diag(it->second, diag::error_inoutput_conflict_with_clobber));
+    }
+    // Check if same register appears in both input list and clobber list
+    for (auto it = InputVars.begin(); it != InputVars.end(); ++it) {
+      if (Clobber == it->first)
+        return StmtError(
+        Diag(it->second, diag::error_inoutput_conflict_with_clobber));
+    }
   }
 
   GCCAsmStmt *NS =
Index: test/Sema/asm.c
===================================================================
--- test/Sema/asm.c
+++ test/Sema/asm.c
@@ -28,6 +28,17 @@
   asm ("nop" : : : "104"); // expected-error {{unknown register name '104' in asm}}
   asm ("nop" : : : "-1"); // expected-error {{unknown register name '-1' in asm}}
   asm ("nop" : : : "+1"); // expected-error {{unknown register name '+1' in asm}}
+  register void *clobber_conflict asm ("%rcx");
+  register void *no_clobber_conflict asm ("%rax");
+  asm ("nop" : "=r" (no_clobber_conflict) : "r" (clobber_conflict) : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" (clobber_conflict) : "r" (no_clobber_conflict) : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" (clobber_conflict) : "r" (clobber_conflict) : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" ("%rcx") : "r" (no_clobber_conflict) : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" (no_clobber_conflict) : "r" ("%rcx") : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" ("%rcx") : "r" ("%rcx") : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" (clobber_conflict) : "r" ("%rcx") : "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" ("%rcx") : "r" ("%rcx") : "%rbx", "%rcx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
+  asm ("nop" : "=r" ("%rcx") : "r" ("%rax") : "%rcx", "%rbx"); // expected-error {{asm-specifier for input or output variable conflicts with asm clobber list}}
 }
 
 // rdar://6094010