dont call mir.post_mono_checks in codegen

compiler/rustc_codegen_cranelift/src/base.rs

@@ -250,17 +250,6 @@ pub(crate) fn verify_func(
 }
 
 fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
- if let Err(err) =
- fx.mir.post_mono_checks(fx.tcx, ty::ParamEnv::reveal_all(), |c| Ok(fx.monomorphize(c)))
- {
- err.emit_err(fx.tcx);
- fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
- fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
- // compilation should have been aborted
- fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
- return;
- }
-
  let arg_uninhabited = fx
  .mir
  .args_iter()

compiler/rustc_codegen_ssa/src/mir/constant.rs

@@ -21,6 +21,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
  }
 
  pub fn eval_mir_constant(&self, constant: &mir::ConstOperand<'tcx>) -> mir::ConstValue<'tcx> {
+ // `MirUsedCollector` visited all constants before codegen began, so if we got here there
+ // can be no more constants that fail to evaluate.
  self.monomorphize(constant.const_)
  .eval(self.cx.tcx(), ty::ParamEnv::reveal_all(), Some(constant.span))
  .expect("erroneous constant not captured by required_consts")

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -209,18 +209,11 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
  caller_location: None,
  };
 
- fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut start_bx);
+ // It may seem like we should iterate over `required_consts` to ensure they all successfully
+ // evaluate; however, the `MirUsedCollector` already did that during the collection phase of
+ // monomorphization so we don't have to do it again.
 
- // Rust post-monomorphization checks; we later rely on them.
- if let Err(err) =
- mir.post_mono_checks(cx.tcx(), ty::ParamEnv::reveal_all(), |c| Ok(fx.monomorphize(c)))
- {
- err.emit_err(cx.tcx());
- // This IR shouldn't ever be emitted, but let's try to guard against any of this code
- // ever running.
- start_bx.abort();
- return;
- }
+ fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut start_bx);
 
  let memory_locals = analyze::non_ssa_locals(&fx);
 

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -750,12 +750,14 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
  // Make sure all the constants required by this frame evaluate successfully (post-monomorphization check).
  if M::POST_MONO_CHECKS {
- // `ctfe_query` does some error message decoration that we want to be in effect here.
- self.ctfe_query(None, |tcx| {
- body.post_mono_checks(*tcx, self.param_env, |c| {
- self.subst_from_current_frame_and_normalize_erasing_regions(c)
- })
- })?;
+ for &const_ in &body.required_consts {
+ let c =
+ self.subst_from_current_frame_and_normalize_erasing_regions(const_.const_)?;
+ c.eval(*self.tcx, self.param_env, Some(const_.span)).map_err(|err| {
+ err.emit_note(*self.tcx);
+ err
+ })?;
+ }
  }
 
  // done
@@ -1054,14 +1056,14 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  Ok(())
  }
 
- /// Call a query that can return `ErrorHandled`. If `span` is `Some`, point to that span when an error occurs.
+ /// Call a query that can return `ErrorHandled`. Should be used for statics and other globals.
+ /// (`mir::Const`/`ty::Const` have `eval` methods that can be used directly instead.)
  pub fn ctfe_query<T>(
  &self,
- span: Option<Span>,
  query: impl FnOnce(TyCtxtAt<'tcx>) -> Result<T, ErrorHandled>,
  ) -> Result<T, ErrorHandled> {
  // Use a precise span for better cycle errors.
- query(self.tcx.at(span.unwrap_or_else(|| self.cur_span()))).map_err(|err| {
+ query(self.tcx.at(self.cur_span())).map_err(|err| {
  err.emit_note(*self.tcx);
  err
  })
@@ -1082,7 +1084,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  } else {
  self.param_env
  };
- let val = self.ctfe_query(None, |tcx| tcx.eval_to_allocation_raw(param_env.and(gid)))?;
+ let val = self.ctfe_query(|tcx| tcx.eval_to_allocation_raw(param_env.and(gid)))?;
  self.raw_const_to_mplace(val)
  }
 
@@ -1092,7 +1094,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  span: Option<Span>,
  layout: Option<TyAndLayout<'tcx>>,
  ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
- let const_val = self.ctfe_query(span, |tcx| val.eval(*tcx, self.param_env, span))?;
+ let const_val = val.eval(*self.tcx, self.param_env, span).map_err(|err| {
+ // FIXME: somehow this is reachable even when POST_MONO_CHECKS is on.
+ // Are we not always populating `required_consts`?
+ err.emit_note(*self.tcx);
+ err
+ })?;
  self.const_val_to_op(const_val, val.ty(), layout)
  }
 

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -164,7 +164,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  sym::type_name => Ty::new_static_str(self.tcx.tcx),
  _ => bug!(),
  };
- let val = self.ctfe_query(None, |tcx| {
+ let val = self.ctfe_query(|tcx| {
  tcx.const_eval_global_id(self.param_env, gid, Some(tcx.span))
  })?;
  let val = self.const_val_to_op(val, ty, Some(dest.layout))?;

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -536,7 +536,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  }
 
  // We don't give a span -- statics don't need that, they cannot be generic or associated.
- let val = self.ctfe_query(None, |tcx| tcx.eval_static_initializer(def_id))?;
+ let val = self.ctfe_query(|tcx| tcx.eval_static_initializer(def_id))?;
  (val, Some(def_id))
  }
  };

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -43,21 +43,6 @@ impl ErrorHandled {
  }
  }
 
- pub fn emit_err(&self, tcx: TyCtxt<'_>) -> ErrorGuaranteed {
- match self {
- &ErrorHandled::Reported(err, span) => {
- if !err.is_tainted_by_errors && !span.is_dummy() {
- tcx.sess.emit_err(error::ErroneousConstant { span });
- }
- err.error
- }
- &ErrorHandled::TooGeneric(span) => tcx.sess.delay_span_bug(
- span,
- "encountered TooGeneric error when monomorphic data was expected",
- ),
- }
- }
-
  pub fn emit_note(&self, tcx: TyCtxt<'_>) {
  match self {
  &ErrorHandled::Reported(err, span) => {

compiler/rustc_middle/src/mir/mod.rs

@@ -2,7 +2,7 @@
 //!
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/mir/index.html
 
-use crate::mir::interpret::{AllocRange, ConstAllocation, ErrorHandled, Scalar};
+use crate::mir::interpret::{AllocRange, ConstAllocation, Scalar};
 use crate::mir::visit::MirVisitable;
 use crate::ty::codec::{TyDecoder, TyEncoder};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
@@ -568,34 +568,6 @@ impl<'tcx> Body<'tcx> {
  pub fn is_custom_mir(&self) -> bool {
  self.injection_phase.is_some()
  }
-
- /// *Must* be called once the full substitution for this body is known, to ensure that the body
- /// is indeed fit for code generation or consumption more generally.
- ///
- /// Sadly there's no nice way to represent an "arbitrary normalizer", so we take one for
- /// constants specifically. (`Option<GenericArgsRef>` could be used for that, but the fact
- /// that `Instance::args_for_mir_body` is private and instead instance exposes normalization
- /// functions makes it seem like exposing the generic args is not the intended strategy.)
- ///
- /// Also sadly, CTFE doesn't even know whether it runs on MIR that is already polymorphic or still monomorphic,
- /// so we cannot just immediately ICE on TooGeneric.
- ///
- /// Returns Ok(()) if everything went fine, and `Err` if a problem occurred and got reported.
- pub fn post_mono_checks(
- &self,
- tcx: TyCtxt<'tcx>,
- param_env: ty::ParamEnv<'tcx>,
- normalize_const: impl Fn(Const<'tcx>) -> Result<Const<'tcx>, ErrorHandled>,
- ) -> Result<(), ErrorHandled> {
- // For now, the only thing we have to check is is to ensure that all the constants used in
- // the body successfully evaluate.
- for &const_ in &self.required_consts {
- let c = normalize_const(const_.const_)?;
- c.eval(tcx, param_env, Some(const_.span))?;
- }
-
- Ok(())
- }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)]

compiler/rustc_middle/src/mir/visit.rs

@@ -184,6 +184,8 @@ macro_rules! make_mir_visitor {
 
  visit_place_fns!($($mutability)?);
 
+ /// This is called for every constant in the MIR body and every `required_consts`
+ /// (i.e., including consts that have been dead-code-eliminated).
  fn visit_constant(
  &mut self,
  constant: & $($mutability)? ConstOperand<'tcx>,

compiler/rustc_monomorphize/src/collector.rs

@@ -1426,6 +1426,8 @@ fn collect_used_items<'tcx>(
  );
  }
 
+ // Here we rely on the visitor also visiting `required_consts`, so that we evaluate them
+ // and abort compilation if any of them errors.
  MirUsedCollector {
  tcx,
  body: &body,

src/tools/miri/src/concurrency/thread.rs

@@ -803,8 +803,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
  if tcx.is_foreign_item(def_id) {
  throw_unsup_format!("foreign thread-local statics are not supported");
  }
- // We don't give a span -- statics don't need that, they cannot be generic or associated.
- let allocation = this.ctfe_query(None, |tcx| tcx.eval_static_initializer(def_id))?;
+ let allocation = this.ctfe_query(|tcx| tcx.eval_static_initializer(def_id))?;
  let mut allocation = allocation.inner().clone();
  // This allocation will be deallocated when the thread dies, so it is not in read-only memory.
  allocation.mutability = Mutability::Mut;