diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 07e19aad34b..1d64b1d859c 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -210,18 +210,18 @@ X86TargetLowering::X86TargetLowering(TargetMachine &TM)
   setOperationAction(ISD::FLT_ROUNDS       , MVT::i32  , Custom);
   
   setOperationAction(ISD::CTPOP            , MVT::i8   , Expand);
-  setOperationAction(ISD::CTTZ             , MVT::i8   , Expand);
-  setOperationAction(ISD::CTLZ             , MVT::i8   , Expand);
+  setOperationAction(ISD::CTTZ             , MVT::i8   , Custom);
+  setOperationAction(ISD::CTLZ             , MVT::i8   , Custom);
   setOperationAction(ISD::CTPOP            , MVT::i16  , Expand);
-  setOperationAction(ISD::CTTZ             , MVT::i16  , Expand);
-  setOperationAction(ISD::CTLZ             , MVT::i16  , Expand);
+  setOperationAction(ISD::CTTZ             , MVT::i16  , Custom);
+  setOperationAction(ISD::CTLZ             , MVT::i16  , Custom);
   setOperationAction(ISD::CTPOP            , MVT::i32  , Expand);
-  setOperationAction(ISD::CTTZ             , MVT::i32  , Expand);
-  setOperationAction(ISD::CTLZ             , MVT::i32  , Expand);
+  setOperationAction(ISD::CTTZ             , MVT::i32  , Custom);
+  setOperationAction(ISD::CTLZ             , MVT::i32  , Custom);
   if (Subtarget->is64Bit()) {
     setOperationAction(ISD::CTPOP          , MVT::i64  , Expand);
-    setOperationAction(ISD::CTTZ           , MVT::i64  , Expand);
-    setOperationAction(ISD::CTLZ           , MVT::i64  , Expand);
+    setOperationAction(ISD::CTTZ           , MVT::i64  , Custom);
+    setOperationAction(ISD::CTLZ           , MVT::i64  , Custom);
   }
 
   setOperationAction(ISD::READCYCLECOUNTER , MVT::i64  , Custom);
@@ -5345,6 +5345,42 @@ SDOperand X86TargetLowering::LowerFLT_ROUNDS(SDOperand Op, SelectionDAG &DAG) {
                       ISD::TRUNCATE : ISD::ZERO_EXTEND), VT, RetVal);
 }
 
+SDOperand X86TargetLowering::LowerCTLZ(SDOperand Op, SelectionDAG &DAG) {
+  MVT::ValueType VT = Op.getValueType();
+  MVT::ValueType OpVT = VT;
+  unsigned NumBits = MVT::getSizeInBits(VT);
+
+  Op = Op.getOperand(0);
+  if (VT == MVT::i8) {
+    OpVT = MVT::i32;
+    Op = DAG.getNode(ISD::ZERO_EXTEND, OpVT, Op);
+  }
+  if (VT == MVT::i32 || VT == MVT::i64)
+    return DAG.getNode(ISD::XOR, OpVT, DAG.getNode(X86ISD::BSR, OpVT, Op),
+                       DAG.getConstant(NumBits-1, OpVT));
+
+  Op = DAG.getNode(ISD::SUB, OpVT, DAG.getConstant(NumBits-1, OpVT),
+                   DAG.getNode(X86ISD::BSR, OpVT, Op));
+  if (VT == MVT::i8)
+    Op = DAG.getNode(ISD::TRUNCATE, MVT::i8, Op);
+  return Op;
+}
+
+SDOperand X86TargetLowering::LowerCTTZ(SDOperand Op, SelectionDAG &DAG) {
+  MVT::ValueType VT = Op.getValueType();
+  MVT::ValueType OpVT = VT;
+
+  Op = Op.getOperand(0);
+  if (VT == MVT::i8) {
+    OpVT = MVT::i32;
+    Op = DAG.getNode(ISD::ZERO_EXTEND, OpVT, Op);
+  }
+  Op = DAG.getNode(X86ISD::BSF, OpVT, Op);
+  if (VT == MVT::i8)
+    Op = DAG.getNode(ISD::TRUNCATE, MVT::i8, Op);
+  return Op;
+}
+
 /// LowerOperation - Provide custom lowering hooks for some operations.
 ///
 SDOperand X86TargetLowering::LowerOperation(SDOperand Op, SelectionDAG &DAG) {
@@ -5387,7 +5423,8 @@ SDOperand X86TargetLowering::LowerOperation(SDOperand Op, SelectionDAG &DAG) {
   case ISD::EH_RETURN:          return LowerEH_RETURN(Op, DAG);
   case ISD::TRAMPOLINE:         return LowerTRAMPOLINE(Op, DAG);
   case ISD::FLT_ROUNDS:         return LowerFLT_ROUNDS(Op, DAG);
-      
+  case ISD::CTLZ:               return LowerCTLZ(Op, DAG);
+  case ISD::CTTZ:               return LowerCTTZ(Op, DAG);
       
   // FIXME: REMOVE THIS WHEN LegalizeDAGTypes lands.
   case ISD::READCYCLECOUNTER:
@@ -5407,6 +5444,8 @@ SDNode *X86TargetLowering::ExpandOperationResult(SDNode *N, SelectionDAG &DAG) {
 const char *X86TargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch (Opcode) {
   default: return NULL;
+  case X86ISD::BSF:                return "X86ISD::BSF";
+  case X86ISD::BSR:                return "X86ISD::BSR";
   case X86ISD::SHLD:               return "X86ISD::SHLD";
   case X86ISD::SHRD:               return "X86ISD::SHRD";
   case X86ISD::FAND:               return "X86ISD::FAND";
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 5fe49f8d81b..c366a461dfc 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -28,6 +28,11 @@ namespace llvm {
       // Start the numbering where the builtin ops leave off.
       FIRST_NUMBER = ISD::BUILTIN_OP_END+X86::INSTRUCTION_LIST_END,
 
+      /// BSF - Bit scan forward.
+      /// BSR - Bit scan reverse.
+      BSF,
+      BSR,
+
       /// SHLD, SHRD - Double shift instructions. These correspond to
       /// X86::SHLDxx and X86::SHRDxx instructions.
       SHLD,
@@ -489,6 +494,8 @@ namespace llvm {
     SDOperand LowerEH_RETURN(SDOperand Op, SelectionDAG &DAG);
     SDOperand LowerTRAMPOLINE(SDOperand Op, SelectionDAG &DAG);
     SDOperand LowerFLT_ROUNDS(SDOperand Op, SelectionDAG &DAG);
+    SDOperand LowerCTLZ(SDOperand Op, SelectionDAG &DAG);
+    SDOperand LowerCTTZ(SDOperand Op, SelectionDAG &DAG);
     SDNode *ExpandFP_TO_SINT(SDNode *N, SelectionDAG &DAG);
     SDNode *ExpandREADCYCLECOUNTER(SDNode *N, SelectionDAG &DAG);
   };
diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 1fb162d0cb2..28ef8388a90 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -57,6 +57,8 @@ def SDT_X86EHRET : SDTypeProfile<0, 1, [SDTCisInt<0>]>;
 
 def SDT_X86TCRET : SDTypeProfile<0, 2, [SDTCisPtrTy<0>, SDTCisVT<1, i32>]>;
 
+def X86bsf     : SDNode<"X86ISD::BSF",      SDTIntUnaryOp>;
+def X86bsr     : SDNode<"X86ISD::BSR",      SDTIntUnaryOp>;
 def X86shld    : SDNode<"X86ISD::SHLD",     SDTIntShiftDOp>;
 def X86shrd    : SDNode<"X86ISD::SHRD",     SDTIntShiftDOp>;
 
@@ -445,6 +447,35 @@ def XCHG32rm : I<0x87, MRMSrcMem,
                  (outs), (ins GR32:$src1, i32mem:$src2),
                  "xchg{l}\t{$src2|$src1}, {$src1|$src2}", []>;
 
+// Bit scan instructions.
+let Defs = [EFLAGS] in {
+def BSF16rr  : I<0xBC, AddRegFrm, (outs GR16:$dst), (ins GR16:$src),
+                 "bsf{w}\t{$src, $dst||$dst, $src}",
+                 [(set GR16:$dst, (X86bsf GR16:$src))]>, TB;
+def BSF16rm  : I<0xBC, MRMSrcMem, (outs GR16:$dst), (ins i16mem:$src),
+                 "bsf{w}\t{$src, $dst||$dst, $src}",
+                 [(set GR16:$dst, (X86bsf (loadi16 addr:$src)))]>, TB;
+def BSF32rr  : I<0xBC, AddRegFrm, (outs GR32:$dst), (ins GR32:$src),
+                 "bsf{l}\t{$src, $dst||$dst, $src}",
+                 [(set GR32:$dst, (X86bsf GR32:$src))]>, TB;
+def BSF32rm  : I<0xBC, MRMSrcMem, (outs GR32:$dst), (ins i32mem:$src),
+                 "bsf{l}\t{$src, $dst||$dst, $src}",
+                 [(set GR32:$dst, (X86bsf (loadi32 addr:$src)))]>, TB;
+
+def BSR16rr  : I<0xBD, AddRegFrm, (outs GR16:$dst), (ins GR16:$src),
+                 "bsr{w}\t{$src, $dst||$dst, $src}",
+                 [(set GR16:$dst, (X86bsr GR16:$src))]>, TB;
+def BSR16rm  : I<0xBD, MRMSrcMem, (outs GR16:$dst), (ins i16mem:$src),
+                 "bsr{w}\t{$src, $dst||$dst, $src}",
+                 [(set GR16:$dst, (X86bsr (loadi16 addr:$src)))]>, TB;
+def BSR32rr  : I<0xBD, AddRegFrm, (outs GR32:$dst), (ins GR32:$src),
+                 "bsr{l}\t{$src, $dst||$dst, $src}",
+                 [(set GR32:$dst, (X86bsr GR32:$src))]>, TB;
+def BSR32rm  : I<0xBD, MRMSrcMem, (outs GR32:$dst), (ins i32mem:$src),
+                 "bsr{l}\t{$src, $dst||$dst, $src}",
+                 [(set GR32:$dst, (X86bsr (loadi32 addr:$src)))]>, TB;
+} // Defs = [EFLAGS]
+
 def LEA16r   : I<0x8D, MRMSrcMem,
                  (outs GR16:$dst), (ins i32mem:$src),
                  "lea{w}\t{$src|$dst}, {$dst|$src}", []>, OpSize;
diff --git a/lib/Target/X86/X86InstrX86-64.td b/lib/Target/X86/X86InstrX86-64.td
index 6dea8401348..f153c4d7a65 100644
--- a/lib/Target/X86/X86InstrX86-64.td
+++ b/lib/Target/X86/X86InstrX86-64.td
@@ -167,6 +167,23 @@ def XCHG64mr : RI<0x87, MRMDestMem, (outs), (ins i64mem:$src1, GR64:$src2),
 def XCHG64rm : RI<0x87, MRMSrcMem, (outs), (ins GR64:$src1, i64mem:$src2),
                   "xchg{q}\t{$src2|$src1}, {$src1|$src2}", []>;
 
+// Bit scan instructions.
+let Defs = [EFLAGS] in {
+def BSF64rr  : RI<0xBC, AddRegFrm, (outs GR64:$dst), (ins GR64:$src),
+                  "bsf{q}\t{$src, $dst||$dst, $src}",
+                  [(set GR64:$dst, (X86bsf GR64:$src))]>, TB;
+def BSF64rm  : RI<0xBC, MRMSrcMem, (outs GR64:$dst), (ins i64mem:$src),
+                  "bsf{q}\t{$src, $dst||$dst, $src}",
+                  [(set GR64:$dst, (X86bsf (loadi64 addr:$src)))]>, TB;
+
+def BSR64rr  : RI<0xBD, AddRegFrm, (outs GR64:$dst), (ins GR64:$src),
+                  "bsr{q}\t{$src, $dst||$dst, $src}",
+                  [(set GR64:$dst, (X86bsr GR64:$src))]>, TB;
+def BSR64rm  : RI<0xBD, MRMSrcMem, (outs GR64:$dst), (ins i64mem:$src),
+                  "bsr{q}\t{$src, $dst||$dst, $src}",
+                  [(set GR64:$dst, (X86bsr (loadi64 addr:$src)))]>, TB;
+} // Defs = [EFLAGS]
+
 // Repeat string ops
 let Defs = [RCX,RDI,RSI], Uses = [RCX,RDI,RSI] in
 def REP_MOVSQ : RI<0xA5, RawFrm, (outs), (ins), "{rep;movsq|rep movsq}",
diff --git a/test/CodeGen/X86/clz.ll b/test/CodeGen/X86/clz.ll
new file mode 100644
index 00000000000..0505529cc48
--- /dev/null
+++ b/test/CodeGen/X86/clz.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep bsr
+; RUN: llvm-as < %s | llc -march=x86 | grep bsf
+
+define i32 @t1(i32 %x) nounwind  {
+	%tmp = tail call i32 @llvm.ctlz.i32( i32 %x )
+	ret i32 %tmp
+}
+
+declare i32 @llvm.ctlz.i32(i32) nounwind readnone 
+
+define i32 @t2(i32 %x) nounwind  {
+	%tmp = tail call i32 @llvm.cttz.i32( i32 %x )
+	ret i32 %tmp
+}
+
+declare i32 @llvm.cttz.i32(i32) nounwind readnone