Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -16677,7 +16677,7 @@
         if ((Count.getOpcode() == ISD::CTTZ ||
              Count.getOpcode() == ISD::CTTZ_ZERO_UNDEF) &&
             N0 == Count.getOperand(0) &&
-            (!LegalOperations || TLI.isOperationLegal(ISD::CTTZ, VT)))
+            (!LegalOperations && TLI.isOperationLegal(ISD::CTTZ, VT)))
           return DAG.getNode(ISD::CTTZ, DL, VT, N0);
         // If the other operand is ctlz/ctlz_zero_undef of N0, and ctlz is
         // legal, combine to just ctlz.
Index: test/CodeGen/AMDGPU/cttz_zero_undef.ll
===================================================================
--- test/CodeGen/AMDGPU/cttz_zero_undef.ll
+++ test/CodeGen/AMDGPU/cttz_zero_undef.ll
@@ -76,3 +76,28 @@
   store <4 x i32> %cttz, <4 x i32> addrspace(1)* %out, align 16
   ret void
 }
+
+; FUNC-LABEL: {{^}}s_cttz_zero_undef_i32_with_select:
+; SI: s_ff1_i32_b32
+; EG: MEM_RAT_CACHELESS STORE_RAW [[RESULT:T[0-9]+\.[XYZW]]]
+; EG: FFBL_INT {{\*? *}}[[RESULT]]
+define amdgpu_kernel void @s_cttz_zero_undef_i32_with_select(i32 addrspace(1)* noalias %out, i32 %val) nounwind {
+  %cttz = tail call i32 @llvm.cttz.i32(i32 %val, i1 true) nounwind readnone
+  %cttz_ret = icmp ne i32 %val, 0
+  %ret = select i1 %cttz_ret, i32 %cttz, i32 32
+  store i32 %cttz, i32 addrspace(1)* %out, align 4
+  ret void
+}
+
+; FUNC-LABEL: {{^}}v_cttz_zero_undef_i32_with_select:
+; SI: v_ffbl_b32_e32
+; EG: MEM_RAT_CACHELESS STORE_RAW [[RESULT:T[0-9]+\.[XYZW]]]
+define amdgpu_kernel void @v_cttz_zero_undef_i32_with_select(i32 addrspace(1)* noalias %out, i32 addrspace(1)* nocapture readonly %arrayidx) nounwind {
+  %val = load i32, i32 addrspace(1)* %arrayidx, align 1
+  %cttz = tail call i32 @llvm.cttz.i32(i32 %val, i1 true) nounwind readnone
+  %cttz_ret = icmp ne i32 %val, 0
+  %ret = select i1 %cttz_ret, i32 %cttz, i32 32
+  store i32 %ret, i32 addrspace(1)* %out, align 4
+  ret void
+}
+