[SLP] Use the correct identity when combining binary opcodes with AND/MUL (#180457)HEADmain

Fixes #180456

Fix bug in the following SLP lowering:
```
define void @sub_mul(ptr %p, ptr %s) {
entry:
  %p1 = getelementptr i16, ptr %p, i64 1

  %l0 = load i16, ptr %p
  %l1 = load i16, ptr %p1

  %mul0 = sub i16 %l0, 0
  %mul1 = mul i16 %l1, 5

  %s1 = getelementptr i16, ptr %s, i64 1

  store i16 %mul0, ptr %s
  store i16 %mul1, ptr %s1
  ret void
}
```
to
```
define void @sub_mul(ptr %p, ptr %s) {
entry:
%tmp0 = load <2 x i16>, ptr %p, align 2
%tmp1 = mul <2 x i16> %tmp0, <i16 0, i16 5> -> updates to <i16 1, i16 5>
store <2 x i16> %tmp1, ptr %s, align 2
ret void
}
```

0 files changed, 0 insertions, 0 deletions