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Add const_eval_select intrinsic

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This commit is contained in:
Deadbeef
2021-10-12 05:06:37 +00:00
parent 0c87288f92
commit 5387b6542f
20 changed files with 334 additions and 38 deletions
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59
compiler/rustc_const_eval/src/const_eval/machine.rs
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@@ -26,14 +26,35 @@ impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
/// "Intercept" a function call to a panic-related function
/// because we have something special to do for it.
/// If this returns successfully (`Ok`), the function should just be evaluated normally.
fn hook_panic_fn(
fn hook_special_const_fn(
&mut self,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
is_const_fn: bool,
) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>> {
// The list of functions we handle here must be in sync with
// `is_lang_panic_fn` in `transform/check_consts/mod.rs`.
// `is_lang_special_const_fn` in `transform/check_consts/mod.rs`.
let def_id = instance.def_id();
if is_const_fn {
if Some(def_id) == self.tcx.lang_items().const_eval_select() {
// redirect to const_eval_select_ct
if let Some(const_eval_select) = self.tcx.lang_items().const_eval_select_ct() {
return Ok(Some(
ty::Instance::resolve(
*self.tcx,
ty::ParamEnv::reveal_all(),
const_eval_select,
instance.substs,
)
.unwrap()
.unwrap(),
));
}
}
return Ok(None);
}
if Some(def_id) == self.tcx.lang_items().panic_fn()
|| Some(def_id) == self.tcx.lang_items().panic_str()
|| Some(def_id) == self.tcx.lang_items().panic_display()
@@ -255,31 +276,31 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
// Only check non-glue functions
if let ty::InstanceDef::Item(def) = instance.def {
let mut is_const_fn = true;
// Execution might have wandered off into other crates, so we cannot do a stability-
// sensitive check here. But we can at least rule out functions that are not const
// at all.
if !ecx.tcx.is_const_fn_raw(def.did) {
// allow calling functions marked with #[default_method_body_is_const].
if !ecx.tcx.has_attr(def.did, sym::default_method_body_is_const) {
// Some functions we support even if they are non-const -- but avoid testing
// that for const fn!
if let Some(new_instance) = ecx.hook_panic_fn(instance, args)? {
// We call another const fn instead.
return Self::find_mir_or_eval_fn(
ecx,
new_instance,
_abi,
args,
_ret,
_unwind,
);
} else {
// We certainly do *not* want to actually call the fn
// though, so be sure we return here.
throw_unsup_format!("calling non-const function `{}`", instance)
}
is_const_fn = false;
}
}
// Some functions we support even if they are non-const -- but avoid testing
// that for const fn!
// `const_eval_select` is a const fn because it must use const trait bounds.
if let Some(new_instance) = ecx.hook_special_const_fn(instance, args, is_const_fn)? {
// We call another const fn instead.
return Self::find_mir_or_eval_fn(ecx, new_instance, _abi, args, _ret, _unwind);
}
if !is_const_fn {
// We certainly do *not* want to actually call the fn
// though, so be sure we return here.
throw_unsup_format!("calling non-const function `{}`", instance)
}
}
// This is a const fn. Call it.
Ok(Some(ecx.load_mir(instance.def, None)?))