diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
@@ -547,22 +548,23 @@
     EmitMSInlineAsmStr(AsmStr, MI, MMI, AP, LocCookie, OS);
 
   // Emit warnings if we use reserved registers on the clobber list, as
-  // that might give surprising results.
-  std::vector<std::string> RestrRegs;
+  // that might lead to undefined behaviour.
+  SmallVector<Register, 8> RestrRegs;
+  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
   // Start with the first operand descriptor, and iterate over them.
   for (unsigned I = InlineAsm::MIOp_FirstOperand, NumOps = MI->getNumOperands();
        I < NumOps; ++I) {
     const MachineOperand &MO = MI->getOperand(I);
-    if (MO.isImm()) {
-      unsigned Flags = MO.getImm();
-      const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
-      if (InlineAsm::getKind(Flags) == InlineAsm::Kind_Clobber &&
-          !TRI->isAsmClobberable(*MF, MI->getOperand(I + 1).getReg())) {
-        RestrRegs.push_back(TRI->getName(MI->getOperand(I + 1).getReg()));
-      }
-      // Skip to one before the next operand descriptor, if it exists.
-      I += InlineAsm::getNumOperandRegisters(Flags);
+    if (!MO.isImm())
+      continue;
+    unsigned Flags = MO.getImm();
+    if (InlineAsm::getKind(Flags) == InlineAsm::Kind_Clobber) {
+      Register Reg = MI->getOperand(I + 1).getReg();
+      if (!TRI->isAsmClobberable(*MF, Reg))
+        RestrRegs.push_back(Reg);
     }
+    // Skip to one before the next operand descriptor, if it exists.
+    I += InlineAsm::getNumOperandRegisters(Flags);
   }
 
   if (!RestrRegs.empty()) {
@@ -572,14 +574,15 @@
         SrcMgr.getMemoryBuffer(BufNum)->getBuffer().begin());
 
     std::string Msg = "inline asm clobber list contains reserved registers: ";
-    for (auto I = RestrRegs.begin(), E = RestrRegs.end(); I != E; I++) {
+    for (auto I = RestrRegs.begin(), E = RestrRegs.end(); I != E; ++I) {
       if(I != RestrRegs.begin())
         Msg += ", ";
-      Msg += *I;
+      Msg += TRI->getName(*I);
     }
-    std::string Note = "Reserved registers on the clobber list may not be "
-                "preserved across the asm statement, and clobbering them may "
-                "lead to undefined behaviour.";
+    const char *Note =
+        "Reserved registers on the clobber list may not be "
+        "preserved across the asm statement, and clobbering them may "
+        "lead to undefined behaviour.";
     SrcMgr.PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
     SrcMgr.PrintMessage(Loc, SourceMgr::DK_Note, Note);
   }