Update ABI in const impls of panic_fn/begin_panic_fn.

Author: anp

src/librustc_mir/const_eval/machine.rs

@@ -177,6 +177,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
 
     fn find_mir_or_eval_fn(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        span: Span,
         instance: ty::Instance<'tcx>,
         args: &[OpTy<'tcx>],
         ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>,
@@ -199,7 +200,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 // Some functions we support even if they are non-const -- but avoid testing
                 // that for const fn!  We certainly do *not* want to actually call the fn
                 // though, so be sure we return here.
-                return if ecx.hook_panic_fn(instance, args, ret)? {
+                return if ecx.hook_panic_fn(span, instance, args)? {
                     Ok(None)
                 } else {
                     throw_unsup_format!("calling non-const function `{}`", instance)

src/librustc_mir/interpret/intrinsics.rs

@@ -366,47 +366,21 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// Returns `true` if an intercept happened.
     pub fn hook_panic_fn(
         &mut self,
+        span: Span,
         instance: ty::Instance<'tcx>,
         args: &[OpTy<'tcx, M::PointerTag>],
-        _ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
     ) -> InterpResult<'tcx, bool> {
         let def_id = instance.def_id();
-        if Some(def_id) == self.tcx.lang_items().panic_fn() {
-            // &'static str, &core::panic::Location { &'static str, u32, u32 }
-            assert!(args.len() == 2);
+        if Some(def_id) == self.tcx.lang_items().panic_fn()
+            || Some(def_id) == self.tcx.lang_items().begin_panic_fn()
+        {
+            // &'static str
+            assert!(args.len() == 1);
 
             let msg_place = self.deref_operand(args[0])?;
             let msg = Symbol::intern(self.read_str(msg_place)?);
-
-            let location = self.deref_operand(args[1])?;
-            let (file, line, col) = (
-                self.mplace_field(location, 0)?,
-                self.mplace_field(location, 1)?,
-                self.mplace_field(location, 2)?,
-            );
-
-            let file_place = self.deref_operand(file.into())?;
-            let file = Symbol::intern(self.read_str(file_place)?);
-            let line = self.read_scalar(line.into())?.to_u32()?;
-            let col = self.read_scalar(col.into())?.to_u32()?;
-            throw_panic!(Panic { msg, file, line, col })
-        } else if Some(def_id) == self.tcx.lang_items().begin_panic_fn() {
-            assert!(args.len() == 2);
-            // &'static str, &core::panic::Location { &'static str, u32, u32 }
-            let msg = args[0];
-            let place = self.deref_operand(args[1])?;
-            let (file, line, col) = (
-                self.mplace_field(place, 0)?,
-                self.mplace_field(place, 1)?,
-                self.mplace_field(place, 2)?,
-            );
-
-            let msg_place = self.deref_operand(msg.into())?;
-            let msg = Symbol::intern(self.read_str(msg_place)?);
-            let file_place = self.deref_operand(file.into())?;
-            let file = Symbol::intern(self.read_str(file_place)?);
-            let line = self.read_scalar(line.into())?.to_u32()?;
-            let col = self.read_scalar(col.into())?.to_u32()?;
+            let span = self.find_closest_untracked_caller_location().unwrap_or(span);
+            let (file, line, col) = self.location_triple_for_span(span);
             throw_panic!(Panic { msg, file, line, col })
         } else {
             return Ok(false);

src/librustc_mir/interpret/intrinsics/caller_location.rs

@@ -9,8 +9,9 @@ use crate::interpret::{
 };
 
 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
-    /// Walks up the callstack from the intrinsic's callsite, searching for the first frame which is
-    /// not `#[track_caller]`.
+    /// Walks up the callstack from the intrinsic's callsite, searching for the first callsite in a
+    /// frame which is not `#[track_caller]`. If the first frame found lacks `#[track_caller]`, then
+    /// `None` is returned and the callsite of the function invocation itself should be used.
     crate fn find_closest_untracked_caller_location(&self) -> Option<Span> {
         let mut caller_span = None;
         for next_caller in self.stack.iter().rev() {
@@ -54,9 +55,14 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     }
 
     pub fn alloc_caller_location_for_span(&mut self, span: Span) -> MPlaceTy<'tcx, M::PointerTag> {
+        let (file, line, column) = self.location_triple_for_span(span);
+        self.alloc_caller_location(file, line, column)
+    }
+
+    pub fn location_triple_for_span(&self, span: Span) -> (Symbol, u32, u32) {
         let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
         let caller = self.tcx.sess.source_map().lookup_char_pos(topmost.lo());
-        self.alloc_caller_location(
+        (
             Symbol::intern(&caller.file.name.to_string()),
             caller.line as u32,
             caller.col_display as u32 + 1,

src/librustc_mir/interpret/machine.rs

@@ -139,6 +139,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
     /// was used.
     fn find_mir_or_eval_fn(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        span: Span,
         instance: ty::Instance<'tcx>,
         args: &[OpTy<'tcx, Self::PointerTag>],
         ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,

src/librustc_mir/interpret/terminator.rs

@@ -238,7 +238,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             | ty::InstanceDef::CloneShim(..)
             | ty::InstanceDef::Item(_) => {
                 // We need MIR for this fn
-                let body = match M::find_mir_or_eval_fn(self, instance, args, ret, unwind)? {
+                let body = match M::find_mir_or_eval_fn(self, span, instance, args, ret, unwind)? {
                     Some(body) => body,
                     None => return Ok(()),
                 };

src/librustc_mir/transform/const_prop.rs

@@ -125,6 +125,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine {
 
     fn find_mir_or_eval_fn(
         _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        _span: Span,
         _instance: ty::Instance<'tcx>,
         _args: &[OpTy<'tcx>],
         _ret: Option<(PlaceTy<'tcx>, BasicBlock)>,