diff --git a/lib/CodeGen/VirtRegMap.cpp b/lib/CodeGen/VirtRegMap.cpp
index 7ce5347..dab0215 100644
--- a/lib/CodeGen/VirtRegMap.cpp
+++ b/lib/CodeGen/VirtRegMap.cpp
@@ -1760,8 +1760,10 @@
           SmallVector<unsigned, 2> KillRegs;
           InvalidateKills(MI, RegKills, KillOps, &KillRegs);
           if (MO.isDead() && !KillRegs.empty()) {
-            // Source register or an implicit super-register use is killed.
-            assert(KillRegs[0] == Dst || TRI->isSubRegister(KillRegs[0], Dst));
+            // Source register or an implicit super/sub-register use is killed.
+            assert(KillRegs[0] == Dst ||
+                   TRI->isSubRegister(KillRegs[0], Dst) ||
+                   TRI->isSuperRegister(KillRegs[0], Dst));
             // Last def is now dead.
             TransferDeadness(&MBB, Dist, Src, RegKills, KillOps);
           }
diff --git a/test/CodeGen/X86/2008-12-01-SpillerAssert.ll b/test/CodeGen/X86/2008-12-01-SpillerAssert.ll
new file mode 100644
index 0000000..81b25da
--- /dev/null
+++ b/test/CodeGen/X86/2008-12-01-SpillerAssert.ll
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | llc -mtriple=x86_64-unknown-linux-gnu
+; PR3124
+
+        %struct.cpuinfo_x86 = type { i8, i8, i8, i8, i32, i8, i8, i8, i32, i32, [9 x i32], [16 x i8], [64 x i8], i32, i32, i32, i64, %struct.cpumask_t, i16, i16, i16, i16, i16, i16, i16, i16, i32 }
+        %struct.cpumask_t = type { [1 x i64] }
+@.str10 = external constant [70 x i8]           ; <[70 x i8]*> [#uses=1]
+
+declare i32 @printk(i8*, ...)
+
+define void @display_cacheinfo(%struct.cpuinfo_x86* %c) nounwind section ".cpuinit.text" {
+entry:
+        %asmtmp = tail call { i32, i32, i32, i32 } asm "cpuid", "={ax},={bx},={cx},={dx},0,2,~{dirflag},~{fpsr},~{flags}"(i32 -2147483643, i32 0) nounwind          ; <{ i32, i32, i32, i32 }> [#uses=0]
+        %0 = tail call i32 (i8*, ...)* @printk(i8* getelementptr ([70 x i8]* @.str10, i32 0, i64 0), i32 0, i32 0, i32 0, i32 0) nounwind           ; <i32> [#uses=0]
+        unreachable
+}