Reduce size of InterpErrorInfo to 8 bytes

Author: tmiasko

Diff for: compiler/rustc_middle/src/mir/interpret/error.rs

@@ -40,29 +40,45 @@ pub fn struct_error<'tcx>(tcx: TyCtxtAt<'tcx>, msg: &str) -> DiagnosticBuilder<'
     struct_span_err!(tcx.sess, tcx.span, E0080, "{}", msg)
 }
 
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(InterpErrorInfo<'_>, 8);
+
 /// Packages the kind of error we got from the const code interpreter
 /// up with a Rust-level backtrace of where the error occurred.
 /// Thsese should always be constructed by calling `.into()` on
 /// a `InterpError`. In `librustc_mir::interpret`, we have `throw_err_*`
 /// macros for this.
 #[derive(Debug)]
-pub struct InterpErrorInfo<'tcx> {
-    pub kind: InterpError<'tcx>,
+pub struct InterpErrorInfo<'tcx>(Box<InterpErrorInfoInner<'tcx>>);
+
+#[derive(Debug)]
+struct InterpErrorInfoInner<'tcx> {
+    kind: InterpError<'tcx>,
     backtrace: Option<Box<Backtrace>>,
 }
 
 impl fmt::Display for InterpErrorInfo<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.kind)
+        write!(f, "{}", self.0.kind)
     }
 }
 
-impl InterpErrorInfo<'_> {
+impl InterpErrorInfo<'tcx> {
     pub fn print_backtrace(&self) {
-        if let Some(backtrace) = self.backtrace.as_ref() {
+        if let Some(backtrace) = self.0.backtrace.as_ref() {
             print_backtrace(backtrace);
         }
     }
+
+    pub fn into_kind(self) -> InterpError<'tcx> {
+        let InterpErrorInfo(box InterpErrorInfoInner { kind, .. }) = self;
+        kind
+    }
+
+    #[inline]
+    pub fn kind(&self) -> &InterpError<'tcx> {
+        &self.0.kind
+    }
 }
 
 fn print_backtrace(backtrace: &Backtrace) {
@@ -108,7 +124,7 @@ impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
             }
         };
 
-        InterpErrorInfo { kind, backtrace }
+        InterpErrorInfo(Box::new(InterpErrorInfoInner { kind, backtrace }))
     }
 }
 

Diff for: compiler/rustc_mir/src/const_eval/error.rs

@@ -84,7 +84,11 @@ impl<'tcx> ConstEvalErr<'tcx> {
     {
         error.print_backtrace();
         let stacktrace = ecx.generate_stacktrace();
-        ConstEvalErr { error: error.kind, stacktrace, span: span.unwrap_or_else(|| ecx.cur_span()) }
+        ConstEvalErr {
+            error: error.into_kind(),
+            stacktrace,
+            span: span.unwrap_or_else(|| ecx.cur_span()),
+        }
     }
 
     pub fn struct_error(

Diff for: compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -230,7 +230,7 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
         };
         return eval_nullary_intrinsic(tcx, key.param_env, def_id, substs).map_err(|error| {
             let span = tcx.def_span(def_id);
-            let error = ConstEvalErr { error: error.kind, stacktrace: vec![], span };
+            let error = ConstEvalErr { error: error.into_kind(), stacktrace: vec![], span };
             error.report_as_error(tcx.at(span), "could not evaluate nullary intrinsic")
         });
     }

Diff for: compiler/rustc_mir/src/const_eval/machine.rs

@@ -245,8 +245,8 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
         Ok(Some(match ecx.load_mir(instance.def, None) {
             Ok(body) => body,
             Err(err) => {
-                if let err_unsup!(NoMirFor(did)) = err.kind {
-                    let path = ecx.tcx.def_path_str(did);
+                if let err_unsup!(NoMirFor(did)) = err.kind() {
+                    let path = ecx.tcx.def_path_str(*did);
                     return Err(ConstEvalErrKind::NeedsRfc(format!(
                         "calling extern function `{}`",
                         path

Diff for: compiler/rustc_mir/src/interpret/intern.rs

@@ -356,7 +356,7 @@ where
                 // an allocation, which we should avoid. When that happens,
                 // dedicated error variants should be introduced instead.
                 assert!(
-                    !error.kind.allocates(),
+                    !error.kind().allocates(),
                     "interning encountered allocating error: {}",
                     error
                 );

Diff for: compiler/rustc_mir/src/interpret/validity.rs

@@ -11,7 +11,7 @@ use std::ops::RangeInclusive;
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
-use rustc_middle::mir::interpret::{InterpError, InterpErrorInfo};
+use rustc_middle::mir::interpret::InterpError;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_span::symbol::{sym, Symbol};
@@ -83,14 +83,17 @@ macro_rules! try_validation {
             Ok(x) => x,
             // We catch the error and turn it into a validation failure. We are okay with
             // allocation here as this can only slow down builds that fail anyway.
-            $( $( Err(InterpErrorInfo { kind: $p, .. }) )|+ =>
-                throw_validation_failure!(
-                    $where,
-                    { $( $what_fmt ),+ } $( expected { $( $expected_fmt ),+ } )?
-                ),
-            )+
-            #[allow(unreachable_patterns)]
-            Err(e) => Err::<!, _>(e)?,
+            Err(e) => match e.kind() {
+                $(
+                    $($p)|+ =>
+                       throw_validation_failure!(
+                            $where,
+                            { $( $what_fmt ),+ } $( expected { $( $expected_fmt ),+ } )?
+                        )
+                ),+,
+                #[allow(unreachable_patterns)]
+                _ => Err::<!, _>(e)?,
+            }
         }
     }};
 }
@@ -877,7 +880,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                     Err(err) => {
                         // For some errors we might be able to provide extra information.
                         // (This custom logic does not fit the `try_validation!` macro.)
-                        match err.kind {
+                        match err.kind() {
                             err_ub!(InvalidUninitBytes(Some(access))) => {
                                 // Some byte was uninitialized, determine which
                                 // element that byte belongs to so we can
@@ -935,10 +938,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         match visitor.visit_value(op) {
             Ok(()) => Ok(()),
             // Pass through validation failures.
-            Err(err) if matches!(err.kind, err_ub!(ValidationFailure { .. })) => Err(err),
+            Err(err) if matches!(err.kind(), err_ub!(ValidationFailure { .. })) => Err(err),
             // Also pass through InvalidProgram, those just indicate that we could not
             // validate and each caller will know best what to do with them.
-            Err(err) if matches!(err.kind, InterpError::InvalidProgram(_)) => Err(err),
+            Err(err) if matches!(err.kind(), InterpError::InvalidProgram(_)) => Err(err),
             // Avoid other errors as those do not show *where* in the value the issue lies.
             Err(err) => {
                 err.print_backtrace();

Diff for: compiler/rustc_mir/src/transform/const_prop.rs

@@ -466,7 +466,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 // an allocation, which we should avoid. When that happens,
                 // dedicated error variants should be introduced instead.
                 assert!(
-                    !error.kind.allocates(),
+                    !error.kind().allocates(),
                     "const-prop encountered allocating error: {}",
                     error
                 );