Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -33424,6 +33424,38 @@
     }
   }
 
+  // Handle (CMOV (ADD (CTTZ X), C), C-1, (X != 0)) ->
+  // (ADD (CMOV (CTTZ X), -1, (X != 0)), C) or
+  // (CMOV C-1, (ADD (CTTZ X), C), (X == 0)) ->
+  // (ADD (CMOV C-1, (CTTZ X), (X == 0)), C)
+  if ((CC == X86::COND_NE && TrueOp.getOpcode() == ISD::ADD &&
+       FalseOp.getOpcode() == ISD::Constant) ||
+      (CC == X86::COND_E && TrueOp.getOpcode() == ISD::Constant &&
+       FalseOp.getOpcode() == ISD::ADD)) {
+    auto *Cnst = CC == X86::COND_E ? dyn_cast<ConstantSDNode>(TrueOp)
+                                   : dyn_cast<ConstantSDNode>(FalseOp);
+    SDValue Add = CC == X86::COND_E ? FalseOp : TrueOp;
+    auto *AddOp1 = dyn_cast<ConstantSDNode>(Add.getOperand(1));
+    SDValue AddOp2 = Add.getOperand(0);
+
+    if (Cnst && AddOp1 &&
+        (AddOp2.getOpcode() == ISD::CTTZ_ZERO_UNDEF ||
+         AddOp2.getOpcode() == ISD::CTTZ)) {
+      APInt Diff = Cnst->getAPIntValue() - AddOp1->getAPIntValue();
+      if (CC == X86::COND_NE) {
+        Add = DAG.getNode(X86ISD::CMOV, DL, Add.getValueType(), AddOp2,
+                          DAG.getConstant(Diff, DL, Add.getValueType()),
+                          DAG.getConstant(CC, DL, MVT::i8), Cond);
+      } else {
+        Add = DAG.getNode(X86ISD::CMOV, DL, Add.getValueType(),
+                          DAG.getConstant(Diff, DL, Add.getValueType()), AddOp2,
+                          DAG.getConstant(CC, DL, MVT::i8), Cond);
+      }
+      return DAG.getNode(X86ISD::ADD, DL, Add.getValueType(), Add,
+                         SDValue(AddOp1, 0));
+    }
+  }
+
   return SDValue();
 }
 
Index: lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- lib/Target/X86/X86InstrInfo.cpp
+++ lib/Target/X86/X86InstrInfo.cpp
@@ -3571,6 +3571,13 @@
   case X86::TZCNT32rr: case X86::TZCNT32rm:
   case X86::TZCNT64rr: case X86::TZCNT64rm:
     return X86::COND_B;
+  case X86::BSF16rr:
+  case X86::BSF16rm:
+  case X86::BSF32rr:
+  case X86::BSF32rm:
+  case X86::BSF64rr:
+  case X86::BSF64rm:
+    return X86::COND_E;
   }
 }
 
Index: test/CodeGen/X86/dagcombine-select.ll
===================================================================
--- test/CodeGen/X86/dagcombine-select.ll
+++ test/CodeGen/X86/dagcombine-select.ll
@@ -279,3 +279,65 @@
   %bo = frem double 5.1, %sel
   ret double %bo
 }
+
+declare i64 @llvm.cttz.i64(i64, i1)
+define i64 @cttz_64_eq_select(i64 %v) nounwind {
+; CHECK-LABEL: cttz_64_eq_select:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    bsfq %rdi, %rcx
+; CHECK-NEXT:    movq $-1, %rax
+; CHECK-NEXT:    cmoveq %rcx, %rax
+; CHECK-NEXT:    addq $6, %rax
+; CHECK-NEXT:    retq
+  %cnt = tail call i64 @llvm.cttz.i64(i64 %v, i1 true)
+  %tobool = icmp eq i64 %v, 0
+  %.op = add nuw nsw i64 %cnt, 6
+  %add = select i1 %tobool, i64 5, i64 %.op
+  ret i64 %add
+}
+
+define i64 @cttz_64_ne_select(i64 %v) nounwind {
+; CHECK-LABEL: cttz_64_ne_select:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    bsfq %rdi, %rcx
+; CHECK-NEXT:    movq $-1, %rax
+; CHECK-NEXT:    cmoveq %rcx, %rax
+; CHECK-NEXT:    addq $6, %rax
+; CHECK-NEXT:    retq
+  %cnt = tail call i64 @llvm.cttz.i64(i64 %v, i1 true)
+  %tobool = icmp ne i64 %v, 0
+  %.op = add nuw nsw i64 %cnt, 6
+  %add = select i1 %tobool, i64 %.op, i64 5
+  ret i64 %add
+}
+
+declare i32 @llvm.cttz.i32(i32, i1)
+define i32 @cttz_32_eq_select(i32 %v) nounwind {
+; CHECK-LABEL: cttz_32_eq_select:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    bsfl %edi, %ecx
+; CHECK-NEXT:    movl $-1, %eax
+; CHECK-NEXT:    cmovel %ecx, %eax
+; CHECK-NEXT:    addl $6, %eax
+; CHECK-NEXT:    retq
+  %cnt = tail call i32 @llvm.cttz.i32(i32 %v, i1 true)
+  %tobool = icmp eq i32 %v, 0
+  %.op = add nuw nsw i32 %cnt, 6
+  %add = select i1 %tobool, i32 5, i32 %.op
+  ret i32 %add
+}
+
+define i32 @cttz_32_ne_select(i32 %v) nounwind {
+; CHECK-LABEL: cttz_32_ne_select:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    bsfl %edi, %ecx
+; CHECK-NEXT:    movl $-1, %eax
+; CHECK-NEXT:    cmovel %ecx, %eax
+; CHECK-NEXT:    addl $6, %eax
+; CHECK-NEXT:    retq
+  %cnt = tail call i32 @llvm.cttz.i32(i32 %v, i1 true)
+  %tobool = icmp ne i32 %v, 0
+  %.op = add nuw nsw i32 %cnt, 6
+  %add = select i1 %tobool, i32 %.op, i32 5
+  ret i32 %add
+}