Index: include/clang/Basic/TargetInfo.h
===================================================================
--- include/clang/Basic/TargetInfo.h
+++ include/clang/Basic/TargetInfo.h
@@ -629,6 +629,12 @@
   StringRef getNormalizedGCCRegisterName(StringRef Name,
                                          bool ReturnCanonical = false) const;
 
+  /// \brief Extracts a register from the passed constraint (if it is a
+  /// single-register constraint) and the asm label expression related to a
+  /// variable in the input or output list of an inline asm statement.
+  ///
+  /// This function is used by Sema in order to diagnose conflicts between
+  /// the clobber list and the input/output lists.
   virtual StringRef getConstraintRegister(StringRef Constraint,
                                           StringRef Expression) const {
     return "";
Index: lib/Basic/Targets/AArch64.h
===================================================================
--- lib/Basic/Targets/AArch64.h
+++ lib/Basic/Targets/AArch64.h
@@ -82,6 +82,11 @@
                              std::string &SuggestedModifier) const override;
   const char *getClobbers() const override;
 
+  StringRef getConstraintRegister(StringRef Constraint,
+                                  StringRef Expression) const override {
+    return Expression;
+  }
+
   int getEHDataRegisterNumber(unsigned RegNo) const override;
 };
 
Index: lib/Basic/Targets/ARM.h
===================================================================
--- lib/Basic/Targets/ARM.h
+++ lib/Basic/Targets/ARM.h
@@ -156,6 +156,11 @@
                              std::string &SuggestedModifier) const override;
   const char *getClobbers() const override;
 
+  StringRef getConstraintRegister(StringRef Constraint,
+                                  StringRef Expression) const override {
+    return Expression;
+  }
+
   CallingConvCheckResult checkCallingConvention(CallingConv CC) const override;
 
   int getEHDataRegisterNumber(unsigned RegNo) const override;
Index: test/Sema/arm-asm.c
===================================================================
--- test/Sema/arm-asm.c
+++ test/Sema/arm-asm.c
@@ -10,3 +10,10 @@
   long long foo = 0, bar = 0;
   asm volatile("INST %0, %1" : "=r"(foo) : "r"(bar));
 }
+
+void test_clobber_conflict(void) {
+  register int x asm("r1");
+  asm volatile("nop" :: "r"(x) : "%r1"); // expected-error {{conflicts with asm clobber list}}
+  asm volatile("nop" :: "l"(x) : "%r1"); // expected-error {{conflicts with asm clobber list}}
+  asm volatile("nop" : "=r"(x) :: "%r1"); // expected-error {{conflicts with asm clobber list}}
+}
Index: test/Sema/arm64-inline-asm.c
===================================================================
--- test/Sema/arm64-inline-asm.c
+++ test/Sema/arm64-inline-asm.c
@@ -7,3 +7,9 @@
 
   asm volatile("USE(%0)" :: "z"(0)); // expected-warning {{value size does not match register size specified by the constraint and modifier}} expected-note {{use constraint modifier "w"}}
 }
+
+void test_clobber_conflict(void) {
+  register long x asm("x1");
+  asm volatile("nop" :: "r"(x) : "%x1"); // expected-error {{conflicts with asm clobber list}}
+  asm volatile("nop" : "=r"(x) :: "%x1"); // expected-error {{conflicts with asm clobber list}}
+}