| Issue |
61549
|
| Summary |
AArch64 miscompile
|
| Labels |
backend:AArch64,
llvm:codegen,
miscompilation
|
| Assignees |
|
| Reporter |
regehr
|
here's a function:
```llvm
define i35 @f(i35 %0) {
%2 = srem i35 1, %0
%3 = call i35 @llvm.ctlz.i35(i35 %2, i1 false)
%4 = lshr i35 %3, 5
ret i35 %4
}
declare i35 @llvm.ctlz.i35(i35, i1 immarg) #0
```
when passed `8` as an argument, it should return `1` because:
```
%2 = 1
%3 = 34
%4 = 1
```
however, when compiled to AArch64 by latest llc we get:
```
_f:
mov w8, #1
sbfx x9, x0, #0, #35
sdiv x10, x8, x9
msub x8, x10, x9, x8
eor x0, x8, #0x1
ret
```
and this returns `0` for the same input, verified using this driver:
```
unsigned long f(unsigned long);
#include <stdio.h>
int main(void) {
unsigned long res = f(8UL);
printf("%lu\n", res);
}
```
cc @nunoplopes
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