[SimplifyCFG] Fold switch to wrapping range check #157113
Description
https://alive2.llvm.org/ce/z/mr3yq_
define i32 @src(i8 range(i8 0, 6) %arg) {
switch i8 %arg, label %else [
i8 0, label %if
i8 4, label %if
i8 5, label %if
]
if:
ret i32 0
else:
ret i32 1
}
define i32 @tgt(i8 %arg) {
%add = add i8 %arg, -1
%cmp2 = icmp ult i8 %add, 3
br i1 %cmp2, label %else, label %if
if:
ret i32 0
else:
ret i32 1
}The known range here allows us to express the switch condition as a wrapping range check.