| Issue |
125990
|
| Summary |
vector miscompile from AArch64 backend
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
regehr
|
please bear with me here, this is the best I could get out of llvm-reduce:
```llvm
define i16 @f(<8 x i16> %0) {
%2 = shufflevector <8 x i16> %0, <8 x i16> zeroinitializer, <8 x i32> <i32 4, i32 5, i32 6, i32 7, i32 9, i32 7, i32 5, i32 3>
%3 = zext <8 x i16> %2 to <8 x i64>
%new0 = add <8 x i64> %3, %3
%last = trunc <8 x i64> %new0 to <8 x i16>
%4 = extractelement <8 x i16> %last, i32 0
ret i16 %4
}
```
Alive thinks (and I agree) that when this is called like this:
```
call i16 @f(<8 x i16> <i16 0, i16 3, i16 3, i16 3, i16 1, i16 3, i16 3, i16 3>)
```
the result should be 2.
but when I compile to AArch64 using current llc I get:
```
_f:
movi.2d v1, #0x00ffff0000ffff
uzp1.4s v0, v0, v0
and.16b v0, v0, v1
add.4s v0, v0, v0
xtn.4h v0, v0
umov.h w0, v0[0]
ret
```
and this -- for that same input -- computes 0
cc @hatsunespica @nunoplopes
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