[CodeGen] Default CTTZ_ZERO_UNDEF/CTLZ_ZERO_UNDEF to Expand in TargetLoweringBase. This is what the majority of the targets want and removes a bunch of code. Set it to Legal explicitly in the few cases where that's the desired behavior.

llvm-svn: 267853
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index dadd312..4839a32 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -97,7 +97,7 @@
          {ISD::BSWAP, ISD::SMUL_LOHI, ISD::UMUL_LOHI,
           ISD::MULHS, ISD::MULHU, ISD::SDIVREM, ISD::UDIVREM, ISD::SHL_PARTS,
           ISD::SRA_PARTS, ISD::SRL_PARTS, ISD::ADDC, ISD::ADDE, ISD::SUBC,
-          ISD::SUBE, ISD::CTLZ_ZERO_UNDEF, ISD::CTTZ_ZERO_UNDEF}) {
+          ISD::SUBE}) {
       setOperationAction(Op, T, Expand);
     }
   }