diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
index c29ee62c83e3..277b1e6d275b 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -400,9 +400,6 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
       const LiveRange *DLR = IntB.getLiveRangeContaining(DefIdx);
       BHasPHIKill |= DLR->valno->hasPHIKill;
       assert(DLR->valno->def == DefIdx);
-      if (BHasSubRegs)
-        // Don't know how to update sub-register live intervals.
-        return false;
       BDeadValNos.push_back(DLR->valno);
       BExtend[DLR->start] = DLR->end;
       JoinedCopies.insert(UseMI);
@@ -418,8 +415,17 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
   DOUT << "\nExtending: "; IntB.print(DOUT, tri_);
 
   // Remove val#'s defined by copies that will be coalesced away.
-  for (unsigned i = 0, e = BDeadValNos.size(); i != e; ++i)
+  for (unsigned i = 0, e = BDeadValNos.size(); i != e; ++i) {
+    VNInfo *DeadVNI = BDeadValNos[i];
+    if (BHasSubRegs) {
+      for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) {
+        LiveInterval &SRLI = li_->getInterval(*SR);
+        const LiveRange *SRLR = SRLI.getLiveRangeContaining(DeadVNI->def);
+        SRLI.removeValNo(SRLR->valno);
+      }
+    }
     IntB.removeValNo(BDeadValNos[i]);
+  }
 
   // Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
   // is updated. Kills are also updated.
@@ -443,7 +449,7 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
 
     // If the IntB live range is assigned to a physical register, and if that
     // physreg has sub-registers, update their live intervals as well. 
-    if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
+    if (BHasSubRegs) {
       for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) {
         LiveInterval &SRLI = li_->getInterval(*SR);
         SRLI.MergeInClobberRange(AI->start, End, li_->getVNInfoAllocator());
diff --git a/llvm/test/CodeGen/X86/2009-03-11-CoalescerBug.ll b/llvm/test/CodeGen/X86/2009-03-11-CoalescerBug.ll
new file mode 100644
index 000000000000..1f5631764b57
--- /dev/null
+++ b/llvm/test/CodeGen/X86/2009-03-11-CoalescerBug.ll
@@ -0,0 +1,85 @@
+; RUN: llvm-as < %s | llc -mtriple=i386-apple-darwin9 -stats |& grep regcoalescing | grep commuting
+
+@lookupTable5B = external global [64 x i32], align 32		; <[64 x i32]*> [#uses=1]
+@lookupTable3B = external global [16 x i32], align 32		; <[16 x i32]*> [#uses=1]
+@disparity0 = external global i32		; <i32*> [#uses=5]
+@disparity1 = external global i32		; <i32*> [#uses=3]
+
+define i32 @calc(i32 %theWord, i32 %k) nounwind {
+entry:
+	%0 = lshr i32 %theWord, 3		; <i32> [#uses=1]
+	%1 = and i32 %0, 31		; <i32> [#uses=1]
+	%2 = shl i32 %k, 5		; <i32> [#uses=1]
+	%3 = or i32 %1, %2		; <i32> [#uses=1]
+	%4 = and i32 %theWord, 7		; <i32> [#uses=1]
+	%5 = shl i32 %k, 3		; <i32> [#uses=1]
+	%6 = or i32 %5, %4		; <i32> [#uses=1]
+	%7 = getelementptr [64 x i32]* @lookupTable5B, i32 0, i32 %3		; <i32*> [#uses=1]
+	%8 = load i32* %7, align 4		; <i32> [#uses=5]
+	%9 = getelementptr [16 x i32]* @lookupTable3B, i32 0, i32 %6		; <i32*> [#uses=1]
+	%10 = load i32* %9, align 4		; <i32> [#uses=5]
+	%11 = and i32 %8, 65536		; <i32> [#uses=1]
+	%12 = icmp eq i32 %11, 0		; <i1> [#uses=1]
+	br i1 %12, label %bb1, label %bb
+
+bb:		; preds = %entry
+	%13 = and i32 %8, 994		; <i32> [#uses=1]
+	%14 = load i32* @disparity0, align 4		; <i32> [#uses=2]
+	store i32 %14, i32* @disparity1, align 4
+	br label %bb8
+
+bb1:		; preds = %entry
+	%15 = lshr i32 %8, 18		; <i32> [#uses=1]
+	%16 = and i32 %15, 1		; <i32> [#uses=1]
+	%17 = load i32* @disparity0, align 4		; <i32> [#uses=4]
+	%18 = icmp eq i32 %16, %17		; <i1> [#uses=1]
+	%not = select i1 %18, i32 0, i32 994		; <i32> [#uses=1]
+	%.masked = and i32 %8, 994		; <i32> [#uses=1]
+	%result.1 = xor i32 %not, %.masked		; <i32> [#uses=2]
+	%19 = and i32 %8, 524288		; <i32> [#uses=1]
+	%20 = icmp eq i32 %19, 0		; <i1> [#uses=1]
+	br i1 %20, label %bb7, label %bb6
+
+bb6:		; preds = %bb1
+	%21 = xor i32 %17, 1		; <i32> [#uses=2]
+	store i32 %21, i32* @disparity1, align 4
+	br label %bb8
+
+bb7:		; preds = %bb1
+	store i32 %17, i32* @disparity1, align 4
+	br label %bb8
+
+bb8:		; preds = %bb7, %bb6, %bb
+	%22 = phi i32 [ %17, %bb7 ], [ %21, %bb6 ], [ %14, %bb ]		; <i32> [#uses=4]
+	%result.0 = phi i32 [ %result.1, %bb7 ], [ %result.1, %bb6 ], [ %13, %bb ]		; <i32> [#uses=2]
+	%23 = and i32 %10, 65536		; <i32> [#uses=1]
+	%24 = icmp eq i32 %23, 0		; <i1> [#uses=1]
+	br i1 %24, label %bb10, label %bb9
+
+bb9:		; preds = %bb8
+	%25 = and i32 %10, 29		; <i32> [#uses=1]
+	%26 = or i32 %result.0, %25		; <i32> [#uses=1]
+	store i32 %22, i32* @disparity0, align 4
+	ret i32 %26
+
+bb10:		; preds = %bb8
+	%27 = lshr i32 %10, 18		; <i32> [#uses=1]
+	%28 = and i32 %27, 1		; <i32> [#uses=1]
+	%29 = icmp eq i32 %28, %22		; <i1> [#uses=1]
+	%not13 = select i1 %29, i32 0, i32 29		; <i32> [#uses=1]
+	%.masked20 = and i32 %10, 29		; <i32> [#uses=1]
+	%.pn = xor i32 %not13, %.masked20		; <i32> [#uses=1]
+	%result.3 = or i32 %.pn, %result.0		; <i32> [#uses=2]
+	%30 = and i32 %10, 524288		; <i32> [#uses=1]
+	%31 = icmp eq i32 %30, 0		; <i1> [#uses=1]
+	br i1 %31, label %bb17, label %bb16
+
+bb16:		; preds = %bb10
+	%32 = xor i32 %22, 1		; <i32> [#uses=1]
+	store i32 %32, i32* @disparity0, align 4
+	ret i32 %result.3
+
+bb17:		; preds = %bb10
+	store i32 %22, i32* @disparity0, align 4
+	ret i32 %result.3
+}