diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index c6f3e319f2f..8deaa1a35d7 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -732,7 +732,9 @@ isRegTiedToUseOperand(unsigned DefOpIdx, unsigned *UseOpIdx) const {
     unsigned DefPart = 0;
     for (unsigned i = 1, e = getNumOperands(); i < e; ) {
       const MachineOperand &FMO = getOperand(i);
-      assert(FMO.isImm());
+      // After the normal asm operands there may be additional imp-def regs.
+      if (!FMO.isImm())
+        return false;
       // Skip over this def.
       unsigned NumOps = InlineAsm::getNumOperandRegisters(FMO.getImm());
       unsigned PrevDef = i + 1;
@@ -788,7 +790,9 @@ isRegTiedToDefOperand(unsigned UseOpIdx, unsigned *DefOpIdx) const {
     unsigned FlagIdx, NumOps=0;
     for (FlagIdx = 1; FlagIdx < UseOpIdx; FlagIdx += NumOps+1) {
       const MachineOperand &UFMO = getOperand(FlagIdx);
-      assert(UFMO.isImm() && "Expecting flag operand on inline asm");
+      // After the normal asm operands there may be additional imp-def regs.
+      if (!UFMO.isImm())
+        return false;
       NumOps = InlineAsm::getNumOperandRegisters(UFMO.getImm());
       assert(NumOps < getNumOperands() && "Invalid inline asm flag");
       if (UseOpIdx < FlagIdx+NumOps+1)
diff --git a/test/CodeGen/X86/2009-07-19-AsmExtraOperands.ll b/test/CodeGen/X86/2009-07-19-AsmExtraOperands.ll
new file mode 100644
index 00000000000..31322cfcf93
--- /dev/null
+++ b/test/CodeGen/X86/2009-07-19-AsmExtraOperands.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | llc -march=x86-64
+; PR4583
+
+define i32 @atomic_cmpset_long(i64* %dst, i64 %exp, i64 %src) nounwind ssp noredzone noimplicitfloat {
+entry:
+	%0 = call i8 asm sideeffect "\09lock ; \09\09\09cmpxchgq $2,$1 ;\09       sete\09$0 ;\09\091:\09\09\09\09# atomic_cmpset_long", "={ax},=*m,r,{ax},*m,~{memory},~{dirflag},~{fpsr},~{flags}"(i64* undef, i64 undef, i64 undef, i64* undef) nounwind		; <i8> [#uses=0]
+	br label %1
+
+; <label>:1		; preds = %entry
+	ret i32 undef
+}