| Issue |
157113
|
| Summary |
[SimplifyCFG] Fold switch to wrapping range check
|
| Labels |
llvm:optimizations,
missed-optimization
|
| Assignees |
|
| Reporter |
nikic
|
https://alive2.llvm.org/ce/z/mr3yq_
```llvm
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.
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