Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -25502,6 +25502,10 @@
         Res.first = DestReg;
         Res.second = &X86::GR64RegClass;
       }
+    } else if (VT != MVT::Other) {
+      // Abort if this was not for a clobber.
+      Res.first = 0;
+      Res.second = nullptr;
     }
   } else if (Res.second == &X86::FR32RegClass ||
              Res.second == &X86::FR64RegClass ||
@@ -25527,6 +25531,15 @@
       Res.second = &X86::VR256RegClass;
     else if (X86::VR512RegClass.hasType(VT))
       Res.second = &X86::VR512RegClass;
+    else if (VT != MVT::Other) {
+      // Abort if this was not for a clobber.
+      Res.first = 0;
+      Res.second = nullptr;
+    }
+  } else if (VT != MVT::Other) {
+    // Abort if this was not for a clobber.
+    Res.first = 0;
+    Res.second = nullptr;
   }
 
   return Res;
Index: test/CodeGen/X86/asm-reject-reg-type-mismatch.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/asm-reject-reg-type-mismatch.ll
@@ -0,0 +1,10 @@
+; RUN: not llc -no-integrated-as %s -o - 2> %t1
+; RUN: FileCheck %s < %t1
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--"
+
+; CHECK: error: couldn't allocate output register for constraint '{ax}'
+define i128 @blup() {
+  %v = tail call i128 asm "", "={ax},0,~{dirflag},~{fpsr},~{flags}"(i128 0)
+  ret i128 %v
+}