[llvm] [LegalizeDAG] Optimize CodeGen for `ISD::CTLZ_ZERO_UNDEF` (PR #83039)

[Simon Pilgrim via llvm-commits]

================
@@ -1517,13 +1510,11 @@ define i32 @cttz_i32_osize(i32 %x) optsize {
 define i32 @cttz_i32_msize(i32 %x) minsize {
 ; X86-LABEL: cttz_i32_msize:
 ; X86:       # %bb.0:
-; X86-NOT:     rep
 ; X86-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: cttz_i32_msize:
 ; X64:       # %bb.0:
-; X64-NOT:     rep
----------------
RKSimon wrote:

Add the NOT checks back (they were manually added after the update script is run)

https://github.com/llvm/llvm-project/pull/83039