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Rollup merge of #129613 - RalfJung:interpret-target-feat, r=saethlin

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interpret: do not make const-eval query result depend on tcx.sess

The check against calling functions with missing target features uses `tcx.sess` to determine which target features are available. However, this can differ between different crates in a crate graph, so the same const-eval query can come to different conclusions about whether a constant evaluates successfully or not -- which is bad, we should consistently get the same result everywhere.
This commit is contained in:
Matthias Krüger 2024-08-28 17:12:17 +02:00 • committed by GitHub
commit 39e840f804
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8 changed files with 70 additions and 62 deletions
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44
compiler/rustc_const_eval/src/interpret/call.rs
View file

@ -311,34 +311,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
Ok(())
}
fn check_fn_target_features(&self, instance: ty::Instance<'tcx>) -> InterpResult<'tcx, ()> {
// Calling functions with `#[target_feature]` is not unsafe on WASM, see #84988
let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
if !self.tcx.sess.target.is_like_wasm
&& attrs
.target_features
.iter()
.any(|feature| !self.tcx.sess.target_features.contains(&feature.name))
{
throw_ub_custom!(
fluent::const_eval_unavailable_target_features_for_fn,
unavailable_feats = attrs
.target_features
.iter()
.filter(|&feature| !feature.implied
&& !self.tcx.sess.target_features.contains(&feature.name))
.fold(String::new(), |mut s, feature| {
if !s.is_empty() {
s.push_str(", ");
}
s.push_str(feature.name.as_str());
s
}),
);
}
Ok(())
}
/// The main entry point for creating a new stack frame: performs ABI checks and initializes
/// arguments.
#[instrument(skip(self), level = "trace")]
@ -360,20 +332,18 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
throw_unsup_format!("calling a c-variadic function is not supported");
}
if M::enforce_abi(self) {
if caller_fn_abi.conv != callee_fn_abi.conv {
throw_ub_custom!(
fluent::const_eval_incompatible_calling_conventions,
callee_conv = format!("{:?}", callee_fn_abi.conv),
caller_conv = format!("{:?}", caller_fn_abi.conv),
)
}
if caller_fn_abi.conv != callee_fn_abi.conv {
throw_ub_custom!(
fluent::const_eval_incompatible_calling_conventions,
callee_conv = format!("{:?}", callee_fn_abi.conv),
caller_conv = format!("{:?}", caller_fn_abi.conv),
)
}
// Check that all target features required by the callee (i.e., from
// the attribute `#[target_feature(enable = ...)]`) are enabled at
// compile time.
self.check_fn_target_features(instance)?;
M::check_fn_target_features(self, instance)?;
if !callee_fn_abi.can_unwind {
// The callee cannot unwind, so force the `Unreachable` unwind handling.

22
compiler/rustc_const_eval/src/interpret/machine.rs
View file

@ -173,11 +173,6 @@ pub trait Machine<'tcx>: Sized {
false
}
/// Whether function calls should be [ABI](CallAbi)-checked.
fn enforce_abi(_ecx: &InterpCx<'tcx, Self>) -> bool {
true
}
/// Whether Assert(OverflowNeg) and Assert(Overflow) MIR terminators should actually
/// check for overflow.
fn ignore_optional_overflow_checks(_ecx: &InterpCx<'tcx, Self>) -> bool;
@ -238,6 +233,13 @@ pub trait Machine<'tcx>: Sized {
unwind: mir::UnwindAction,
) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>>;
/// Check whether the given function may be executed on the current machine, in terms of the
/// target features is requires.
fn check_fn_target_features(
_ecx: &InterpCx<'tcx, Self>,
_instance: ty::Instance<'tcx>,
) -> InterpResult<'tcx>;
/// Called to evaluate `Assert` MIR terminators that trigger a panic.
fn assert_panic(
ecx: &mut InterpCx<'tcx, Self>,
@ -617,6 +619,16 @@ pub macro compile_time_machine(<$tcx: lifetime>) {
unreachable!("unwinding cannot happen during compile-time evaluation")
}
#[inline(always)]
fn check_fn_target_features(
_ecx: &InterpCx<$tcx, Self>,
_instance: ty::Instance<$tcx>,
) -> InterpResult<$tcx> {
// For now we don't do any checking here. We can't use `tcx.sess` because that can differ
// between crates, and we need to ensure that const-eval always behaves the same.
Ok(())
}
#[inline(always)]
fn call_extra_fn(
_ecx: &mut InterpCx<$tcx, Self>,