compiler/rustc_borrowck/src/region_infer/dump_mir.rs

   1 #![deny(rustc::untranslatable_diagnostic)]
   2 #![deny(rustc::diagnostic_outside_of_impl)]
   3 //! As part of generating the regions, if you enable `-Zdump-mir=nll`,
   4 //! we will generate an annotated copy of the MIR that includes the
   5 //! state of region inference. This code handles emitting the region
   6 //! context internal state.
   7
   8 use super::{OutlivesConstraint, RegionInferenceContext};
   9 use crate::type_check::Locations;
  10 use rustc_infer::infer::NllRegionVariableOrigin;
  11 use rustc_middle::ty::TyCtxt;
  12 use std::io::{self, Write};
  13
  14 // Room for "'_#NNNNr" before things get misaligned.
  15 // Easy enough to fix if this ever doesn't seem like
  16 // enough.
  17 const REGION_WIDTH: usize = 8;
  18
  19 impl<'tcx> RegionInferenceContext<'tcx> {
  20     /// Write out our state into the `.mir` files.
  21     pub(crate) fn dump_mir(&self, tcx: TyCtxt<'tcx>, out: &mut dyn Write) -> io::Result<()> {
  22         writeln!(out, "| Free Region Mapping")?;
  23
  24         for region in self.regions() {
  25             if let NllRegionVariableOrigin::FreeRegion = self.definitions[region].origin {
  26                 let classification = self.universal_regions.region_classification(region).unwrap();
  27                 let outlived_by = self.universal_region_relations.regions_outlived_by(region);
  28                 writeln!(
  29                     out,
  30                     "| {r:rw$?} | {c:cw$?} | {ob:?}",
  31                     r = region,
  32                     rw = REGION_WIDTH,
  33                     c = classification,
  34                     cw = 8, // "External" at most
  35                     ob = outlived_by
  36                 )?;
  37             }
  38         }
  39
  40         writeln!(out, "|")?;
  41         writeln!(out, "| Inferred Region Values")?;
  42         for region in self.regions() {
  43             writeln!(
  44                 out,
  45                 "| {r:rw$?} | {ui:4?} | {v}",
  46                 r = region,
  47                 rw = REGION_WIDTH,
  48                 ui = self.region_universe(region),
  49                 v = self.region_value_str(region),
  50             )?;
  51         }
  52
  53         writeln!(out, "|")?;
  54         writeln!(out, "| Inference Constraints")?;
  55         self.for_each_constraint(tcx, &mut |msg| writeln!(out, "| {}", msg))?;
  56
  57         Ok(())
  58     }
  59
  60     /// Debugging aid: Invokes the `with_msg` callback repeatedly with
  61     /// our internal region constraints. These are dumped into the
  62     /// -Zdump-mir file so that we can figure out why the region
  63     /// inference resulted in the values that it did when debugging.
  64     fn for_each_constraint(
  65         &self,
  66         tcx: TyCtxt<'tcx>,
  67         with_msg: &mut dyn FnMut(&str) -> io::Result<()>,
  68     ) -> io::Result<()> {
  69         for region in self.definitions.indices() {
  70             let value = self.liveness_constraints.region_value_str(region);
  71             if value != "{}" {
  72                 with_msg(&format!("{:?} live at {}", region, value))?;
  73             }
  74         }
  75
  76         let mut constraints: Vec<_> = self.constraints.outlives().iter().collect();
  77         constraints.sort_by_key(|c| (c.sup, c.sub));
  78         for constraint in &constraints {
  79             let OutlivesConstraint { sup, sub, locations, category, span, .. } = constraint;
  80             let (name, arg) = match locations {
  81                 Locations::All(span) => {
  82                     ("All", tcx.sess.source_map().span_to_embeddable_string(*span))
  83                 }
  84                 Locations::Single(loc) => ("Single", format!("{:?}", loc)),
  85             };
  86             with_msg(&format!(
  87                 "{:?}: {:?} due to {:?} at {}({}) ({:?}",
  88                 sup, sub, category, name, arg, span
  89             ))?;
  90         }
  91
  92         Ok(())
  93     }
  94 }