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Stop using the const_eval query for initializers of statics

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As a side effect, we now represent most promoteds as `ConstValue::Scalar` again. This is useful because all implict promoteds are just references anyway and most explicit promoteds are numeric arguments to `asm!` or SIMD instructions.
This commit is contained in:
Oliver Scherer 2020-07-31 13:27:54 +02:00
parent 083f1d7a37
commit 2d7ac728e4
17 changed files with 53 additions and 108 deletions
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31
compiler/rustc_mir/src/const_eval/eval_queries.rs
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@ -182,7 +182,7 @@ pub(super) fn op_to_const<'tcx>(
}
}
fn validate_and_turn_into_const<'tcx>(
fn turn_into_const<'tcx>(
tcx: TyCtxt<'tcx>,
constant: RawConst<'tcx>,
key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
@ -191,30 +191,21 @@ fn validate_and_turn_into_const<'tcx>(
let def_id = cid.instance.def.def_id();
let is_static = tcx.is_static(def_id);
let ecx = mk_eval_cx(tcx, tcx.def_span(key.value.instance.def_id()), key.param_env, is_static);
let val = (|| {
let mplace = ecx.raw_const_to_mplace(constant)?;
// Turn this into a proper constant.
// Statics/promoteds are always `ByRef`, for the rest `op_to_const` decides
// whether they become immediates.
if is_static || cid.promoted.is_some() {
let ptr = mplace.ptr.assert_ptr();
Ok(ConstValue::ByRef {
alloc: ecx.tcx.global_alloc(ptr.alloc_id).unwrap_memory(),
offset: ptr.offset,
})
} else {
Ok(op_to_const(&ecx, mplace.into()))
}
})();
// FIXME: Can this ever be an error and not be a compiler bug or can we just ICE here?
val.map_err(|error| {
let mplace = ecx.raw_const_to_mplace(constant).map_err(|error| {
// FIXME: Can the above ever error and not be a compiler bug or can we just ICE here?
let err = ConstEvalErr::new(&ecx, error, None);
err.struct_error(ecx.tcx, "it is undefined behavior to use this value", |mut diag| {
diag.note(note_on_undefined_behavior_error());
diag.emit();
})
})
})?;
assert!(
!is_static || cid.promoted.is_some(),
"the const eval query should not be used for statics, use `const_eval_raw` instead"
);
// Turn this into a proper constant.
Ok(op_to_const(&ecx, mplace.into()))
}
pub fn const_eval_validated_provider<'tcx>(
@ -248,7 +239,7 @@ pub fn const_eval_validated_provider<'tcx>(
});
}
tcx.const_eval_raw(key).and_then(|val| validate_and_turn_into_const(tcx, val, key))
tcx.const_eval_raw(key).and_then(|val| turn_into_const(tcx, val, key))
}
pub fn const_eval_raw_provider<'tcx>(