Stream: git-cranelift

Topic: cranelift / Issue #1237 Legalization with isplit as last ...

GitHub (Feb 28 2020 at 23:27):

alexcrichton transferred Issue #1237:

• What are the steps to reproduce the issue? Can you include a CLIF test case,
  ideally reduced with the bugpoint clif-util command?

1. Add the following as legalization:

```rust
for &(ty, ty_half) in &[(I64, I32), (I128, I64)] {
    let inst = ireduce.bind(ty_half).bind(ty);
    expand.legalize(
        def!(a = inst(x)),
        vec![
            def!((a, xh) = isplit(x)),
        ]
    )
}
```

2. Try to compile:

```
test run
target x86_64

function u0:0() -> i64 system_v {
ebb0:
    v0 = iconst.i64 0
    v2 = iconcat v0, v0
    v3 = ireduce.i64 v2
    return v3
}
; run
```

• What do you expect to happen? What does actually happen? Does it panic, and
  if so, with which assertion?

I expected the `ireduce` to be legalized to `v3, v999 = isplit v2`. The result however was a verifier error:

```
function u0:0() -> i64 [%rax] system_v {
                                ebb0:
[RexOp1pu_id#b8]                    v0 = iconst.i64 0
[-]                                 v2 = iconcat v0, v0
[Op1ret#c3]                         return v3
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
; error: inst3: v3 is defined by inst2 which has no EBB

}
```

The problem is that the following legalization code is generated:

```rust
pos.func.dfg.clear_results(inst);
let curpos = pos.position();
let srcloc = pos.srcloc();
let (a, xh) = split::isplit(pos.func, cfg, curpos, srcloc, x);
let removed = pos.remove_inst();
debug_assert_eq!(removed, inst);
return true;
```

The inst results are never attached to an instruction again, nor turned into aliases.

• Which Cranelift version / commit hash / branch are you using? master

Last updated: Dec 23 2024 at 14:03 UTC