diff --git a/llvm/lib/CodeGen/RegAllocFast.cpp b/llvm/lib/CodeGen/RegAllocFast.cpp
--- a/llvm/lib/CodeGen/RegAllocFast.cpp
+++ b/llvm/lib/CodeGen/RegAllocFast.cpp
@@ -359,7 +359,13 @@
   // If this block loops back to itself, it is necessary to check whether the
   // use comes after the def.
   if (MBB->isSuccessor(MBB)) {
-    SelfLoopDef = MRI->getUniqueVRegDef(VirtReg);
+    // Find the first the def in the self loop MBB.
+    for (const MachineInstr &DefInst : MRI->def_instructions(VirtReg)) {
+      if (DefInst.getParent() == MBB) {
+        if (!SelfLoopDef || dominates(*MBB, DefInst.getIterator(), SelfLoopDef))
+          SelfLoopDef = &DefInst;
+      }
+    }
     if (!SelfLoopDef) {
       MayLiveAcrossBlocks.set(Register::virtReg2Index(VirtReg));
       return true;
diff --git a/llvm/test/CodeGen/X86/fastregalloc-selfloop.mir b/llvm/test/CodeGen/X86/fastregalloc-selfloop.mir
--- a/llvm/test/CodeGen/X86/fastregalloc-selfloop.mir
+++ b/llvm/test/CodeGen/X86/fastregalloc-selfloop.mir
@@ -14,11 +14,10 @@
 machineFunctionInfo: {}
 body:             |
   bb.0.entry:
-    ; CHECK: renamable $xmm1 = V_SET0
+    ; CHECK:      renamable $xmm1 = V_SET0
     ; CHECK-NEXT: renamable $xmm0 = V_SET0
     ; CHECK-NEXT: renamable $xmm1 = PXORrr renamable $xmm1, renamable $xmm0
-    ; CHECK-NEXT: MOVAPSmr %stack.1, 1, $noreg, 0, $noreg, $xmm1 :: (store (s128) into %stack.1)
-    ; CHECK-NEXT: MOVAPSmr %stack.0, 1, $noreg, 0, $noreg, renamable $xmm1
+    ; CHECK-NEXT: MOVAPSmr %stack.0, 1, $noreg, 0, $noreg, killed renamable $xmm1
     ; CHECK-NEXT: MOVAPSmr %stack.0, 1, $noreg, 16, $noreg, killed renamable $xmm0
 
     %0:vr128 = V_SET0