diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index 458a2134bf4..ec149dddc1d 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -478,7 +478,8 @@ static void ResurrectConfirmedKill(unsigned Reg, const TargetRegisterInfo* TRI,
   if (!RegKills[KReg])
     return;
 
-  assert(KillOps[KReg] == KillOp && "invalid superreg kill flags");
+  assert(KillOps[KReg]->getParent() == KillOp->getParent() &&
+         "invalid superreg kill flags");
   KillOps[KReg] = NULL;
   RegKills.reset(KReg);
 
@@ -487,7 +488,8 @@ static void ResurrectConfirmedKill(unsigned Reg, const TargetRegisterInfo* TRI,
   for (const unsigned *SR = TRI->getSubRegisters(KReg); *SR; ++SR) {
     DEBUG(dbgs() << "  Resurrect subreg " << TRI->getName(*SR) << "\n");
 
-    assert(KillOps[*SR] == KillOp && "invalid subreg kill flags");
+    assert(KillOps[*SR]->getParent() == KillOp->getParent() &&
+           "invalid subreg kill flags");
     KillOps[*SR] = NULL;
     RegKills.reset(*SR);
   }
diff --git a/test/CodeGen/X86/2011-02-21-VirtRegRewriter-KillSubReg.ll b/test/CodeGen/X86/2011-02-21-VirtRegRewriter-KillSubReg.ll
new file mode 100644
index 00000000000..f982723781e
--- /dev/null
+++ b/test/CodeGen/X86/2011-02-21-VirtRegRewriter-KillSubReg.ll
@@ -0,0 +1,50 @@
+; RUN: llc < %s -O2 -march=x86 -mtriple=i386-pc-linux-gnu -relocation-model=pic | FileCheck %s
+; PR9237: Assertion in VirtRegRewriter.cpp, ResurrectConfirmedKill
+;         `KillOps[*SR] == KillOp && "invalid subreg kill flags"'
+
+%t = type { i32 }
+
+define i32 @foo(%t* %s) nounwind {
+entry:
+  br label %if.then735
+
+if.then735:
+  %call747 = call i32 undef(%t* %s, i8* null, i8* undef, i32 128, i8* undef, i32 516) nounwind
+  br i1 undef, label %if.then751, label %if.then758
+
+if.then751:
+  unreachable
+
+if.then758:
+  %add761 = add i32 %call747, 4
+  %add763 = add i32 %add761, %call747
+  %add.ptr768 = getelementptr inbounds [516 x i8]* null, i32 0, i32 %add761
+  br i1 undef, label %cond.false783, label %cond.true771
+
+cond.true771:
+  %call782 = call i8* @__memmove_chk(i8* %add.ptr768, i8* undef, i32 %call747, i32 undef)
+  br label %cond.end791
+
+; CHECK: calll __memmove_chk
+cond.false783:
+  %call.i1035 = call i8* @__memmove_chk(i8* %add.ptr768, i8* undef, i32 %call747, i32 undef) nounwind
+  br label %cond.end791
+
+cond.end791:
+  %conv801 = trunc i32 %call747 to i8
+  %add.ptr822.sum = add i32 %call747, 3
+  %arrayidx833 = getelementptr inbounds [516 x i8]* null, i32 0, i32 %add.ptr822.sum
+  store i8 %conv801, i8* %arrayidx833, align 1
+  %cmp841 = icmp eq i8* undef, null
+  br i1 %cmp841, label %if.end849, label %if.then843
+
+if.then843:
+  unreachable
+
+if.end849:
+  %call921 = call i32 undef(%t* %s, i8* undef, i8* undef, i32 %add763) nounwind
+  unreachable
+
+}
+
+declare i8* @__memmove_chk(i8*, i8*, i32, i32) nounwind