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Rollup merge of rust-lang#136031 - lqd:polonius-debugger-episode-1, r…
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…=compiler-errors

Expand polonius MIR dump

This PR starts expanding the polonius MIR:
- switches to an HTML file, to show graphs in the same document as the MIR dump, share them more easily since it's a single file that can be hosted as a gist, and also to allow for interactivity in the near future.
- adds the regular NLL MIR + polonius constraints
- embeds a mermaid version of the CFG, similar to the graphviz one, but that needs a smaller js than `dot`'s emscripten js from graphvizonline

[Here's an example](https://gistpreview.github.io/?0c18f2a59b5e24ac0f96447aa34ffe00) of how it looks.

---
In future PRs: mermaid graphs of the NLL region graph, of the NLL SCCs, of the polonius localized outlives constraints, and the interactive polonius MIR dump.

r? `@matthewjasper`
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@matthiaskrgr
matthiaskrgr authored Jan 25, 2025
2 parents 617f49e + 09fb70a commit 30a7740
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181 changes: 170 additions & 11 deletions compiler/rustc_borrowck/src/polonius/dump.rs
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
use std::io;

use rustc_middle::mir::pretty::{PrettyPrintMirOptions, dump_mir_with_options};
use rustc_middle::mir::{Body, ClosureRegionRequirements, PassWhere};
use rustc_middle::mir::pretty::{
PassWhere, PrettyPrintMirOptions, create_dump_file, dump_enabled, dump_mir_to_writer,
};
use rustc_middle::mir::{Body, ClosureRegionRequirements};
use rustc_middle::ty::TyCtxt;
use rustc_session::config::MirIncludeSpans;

Expand All @@ -10,9 +12,6 @@ use crate::polonius::{LocalizedOutlivesConstraint, LocalizedOutlivesConstraintSe
use crate::{BorrowckInferCtxt, RegionInferenceContext};

/// `-Zdump-mir=polonius` dumps MIR annotated with NLL and polonius specific information.
// Note: this currently duplicates most of NLL MIR, with some additions for the localized outlives
// constraints. This is ok for now as this dump will change in the near future to an HTML file to
// become more useful.
pub(crate) fn dump_polonius_mir<'tcx>(
infcx: &BorrowckInferCtxt<'tcx>,
body: &Body<'tcx>,
Expand All @@ -26,25 +25,113 @@ pub(crate) fn dump_polonius_mir<'tcx>(
return;
}

if !dump_enabled(tcx, "polonius", body.source.def_id()) {
return;
}

let localized_outlives_constraints = localized_outlives_constraints
.expect("missing localized constraints with `-Zpolonius=next`");

// We want the NLL extra comments printed by default in NLL MIR dumps (they were removed in
// #112346). Specifying `-Z mir-include-spans` on the CLI still has priority: for example,
// they're always disabled in mir-opt tests to make working with blessed dumps easier.
let _: io::Result<()> = try {
let mut file = create_dump_file(tcx, "html", false, "polonius", &0, body)?;
emit_polonius_dump(
tcx,
body,
regioncx,
borrow_set,
localized_outlives_constraints,
closure_region_requirements,
&mut file,
)?;
};
}

/// The polonius dump consists of:
/// - the NLL MIR
/// - the list of polonius localized constraints
/// - a mermaid graph of the CFG
fn emit_polonius_dump<'tcx>(
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
regioncx: &RegionInferenceContext<'tcx>,
borrow_set: &BorrowSet<'tcx>,
localized_outlives_constraints: LocalizedOutlivesConstraintSet,
closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
out: &mut dyn io::Write,
) -> io::Result<()> {
// Prepare the HTML dump file prologue.
writeln!(out, "<!DOCTYPE html>")?;
writeln!(out, "<html>")?;
writeln!(out, "<head><title>Polonius MIR dump</title></head>")?;
writeln!(out, "<body>")?;

// Section 1: the NLL + Polonius MIR.
writeln!(out, "<div>")?;
writeln!(out, "Raw MIR dump")?;
writeln!(out, "<code><pre>")?;
emit_html_mir(
tcx,
body,
regioncx,
borrow_set,
localized_outlives_constraints,
closure_region_requirements,
out,
)?;
writeln!(out, "</pre></code>")?;
writeln!(out, "</div>")?;

// Section 2: mermaid visualization of the CFG.
writeln!(out, "<div>")?;
writeln!(out, "Control-flow graph")?;
writeln!(out, "<code><pre class='mermaid'>")?;
emit_mermaid_cfg(body, out)?;
writeln!(out, "</pre></code>")?;
writeln!(out, "</div>")?;

// Finalize the dump with the HTML epilogue.
writeln!(
out,
"<script src='https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js'></script>"
)?;
writeln!(out, "<script>")?;
writeln!(out, "mermaid.initialize({{ startOnLoad: false, maxEdges: 100 }});")?;
writeln!(out, "mermaid.run({{ querySelector: '.mermaid' }})")?;
writeln!(out, "</script>")?;
writeln!(out, "</body>")?;
writeln!(out, "</html>")?;

Ok(())
}

/// Emits the polonius MIR, as escaped HTML.
fn emit_html_mir<'tcx>(
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
regioncx: &RegionInferenceContext<'tcx>,
borrow_set: &BorrowSet<'tcx>,
localized_outlives_constraints: LocalizedOutlivesConstraintSet,
closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
out: &mut dyn io::Write,
) -> io::Result<()> {
// Buffer the regular MIR dump to be able to escape it.
let mut buffer = Vec::new();

// We want the NLL extra comments printed by default in NLL MIR dumps. Specifying `-Z
// mir-include-spans` on the CLI still has priority.
let options = PrettyPrintMirOptions {
include_extra_comments: matches!(
tcx.sess.opts.unstable_opts.mir_include_spans,
MirIncludeSpans::On | MirIncludeSpans::Nll
),
};

dump_mir_with_options(
dump_mir_to_writer(
tcx,
false,
"polonius",
&0,
body,
&mut buffer,
|pass_where, out| {
emit_polonius_mir(
tcx,
Expand All @@ -57,7 +144,27 @@ pub(crate) fn dump_polonius_mir<'tcx>(
)
},
options,
);
)?;

// Escape the handful of characters that need it. We don't need to be particularly efficient:
// we're actually writing into a buffered writer already. Note that MIR dumps are valid UTF-8.
let buffer = String::from_utf8_lossy(&buffer);
for ch in buffer.chars() {
let escaped = match ch {
'>' => "&gt;",
'<' => "&lt;",
'&' => "&amp;",
'\'' => "&#39;",
'"' => "&quot;",
_ => {
// The common case, no escaping needed.
write!(out, "{}", ch)?;
continue;
}
};
write!(out, "{}", escaped)?;
}
Ok(())
}

/// Produces the actual NLL + Polonius MIR sections to emit during the dumping process.
Expand Down Expand Up @@ -102,3 +209,55 @@ fn emit_polonius_mir<'tcx>(

Ok(())
}

/// Emits a mermaid flowchart of the CFG blocks and edges, similar to the graphviz version.
fn emit_mermaid_cfg(body: &Body<'_>, out: &mut dyn io::Write) -> io::Result<()> {
use rustc_middle::mir::{TerminatorEdges, TerminatorKind};

// The mermaid chart type: a top-down flowchart.
writeln!(out, "flowchart TD")?;

// Emit the block nodes.
for (block_idx, block) in body.basic_blocks.iter_enumerated() {
let block_idx = block_idx.as_usize();
let cleanup = if block.is_cleanup { " (cleanup)" } else { "" };
writeln!(out, "{block_idx}[\"bb{block_idx}{cleanup}\"]")?;
}

// Emit the edges between blocks, from the terminator edges.
for (block_idx, block) in body.basic_blocks.iter_enumerated() {
let block_idx = block_idx.as_usize();
let terminator = block.terminator();
match terminator.edges() {
TerminatorEdges::None => {}
TerminatorEdges::Single(bb) => {
writeln!(out, "{block_idx} --> {}", bb.as_usize())?;
}
TerminatorEdges::Double(bb1, bb2) => {
if matches!(terminator.kind, TerminatorKind::FalseEdge { .. }) {
writeln!(out, "{block_idx} --> {}", bb1.as_usize())?;
writeln!(out, "{block_idx} -- imaginary --> {}", bb2.as_usize())?;
} else {
writeln!(out, "{block_idx} --> {}", bb1.as_usize())?;
writeln!(out, "{block_idx} -- unwind --> {}", bb2.as_usize())?;
}
}
TerminatorEdges::AssignOnReturn { return_, cleanup, .. } => {
for to_idx in return_ {
writeln!(out, "{block_idx} --> {}", to_idx.as_usize())?;
}

if let Some(to_idx) = cleanup {
writeln!(out, "{block_idx} -- unwind --> {}", to_idx.as_usize())?;
}
}
TerminatorEdges::SwitchInt { targets, .. } => {
for to_idx in targets.all_targets() {
writeln!(out, "{block_idx} --> {}", to_idx.as_usize())?;
}
}
}
}

Ok(())
}
63 changes: 42 additions & 21 deletions compiler/rustc_middle/src/mir/pretty.rs
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,7 @@
use std::collections::BTreeSet;
use std::fmt::{Display, Write as _};
use std::fs;
use std::io::{self, Write as _};
use std::path::{Path, PathBuf};
use std::{fs, io};

use rustc_abi::Size;
use rustc_ast::InlineAsmTemplatePiece;
Expand Down Expand Up @@ -149,37 +148,59 @@ pub fn dump_enabled(tcx: TyCtxt<'_>, pass_name: &str, def_id: DefId) -> bool {
// `def_path_str()` would otherwise trigger `type_of`, and this can
// run while we are already attempting to evaluate `type_of`.

/// Most use-cases of dumping MIR should use the [dump_mir] entrypoint instead, which will also
/// check if dumping MIR is enabled, and if this body matches the filters passed on the CLI.
///
/// That being said, if the above requirements have been validated already, this function is where
/// most of the MIR dumping occurs, if one needs to export it to a file they have created with
/// [create_dump_file], rather than to a new file created as part of [dump_mir], or to stdout/stderr
/// for debugging purposes.
pub fn dump_mir_to_writer<'tcx, F>(
tcx: TyCtxt<'tcx>,
pass_name: &str,
disambiguator: &dyn Display,
body: &Body<'tcx>,
w: &mut dyn io::Write,
mut extra_data: F,
options: PrettyPrintMirOptions,
) -> io::Result<()>
where
F: FnMut(PassWhere, &mut dyn io::Write) -> io::Result<()>,
{
// see notes on #41697 above
let def_path =
ty::print::with_forced_impl_filename_line!(tcx.def_path_str(body.source.def_id()));
// ignore-tidy-odd-backticks the literal below is fine
write!(w, "// MIR for `{def_path}")?;
match body.source.promoted {
None => write!(w, "`")?,
Some(promoted) => write!(w, "::{promoted:?}`")?,
}
writeln!(w, " {disambiguator} {pass_name}")?;
if let Some(ref layout) = body.coroutine_layout_raw() {
writeln!(w, "/* coroutine_layout = {layout:#?} */")?;
}
writeln!(w)?;
extra_data(PassWhere::BeforeCFG, w)?;
write_user_type_annotations(tcx, body, w)?;
write_mir_fn(tcx, body, &mut extra_data, w, options)?;
extra_data(PassWhere::AfterCFG, w)
}

fn dump_matched_mir_node<'tcx, F>(
tcx: TyCtxt<'tcx>,
pass_num: bool,
pass_name: &str,
disambiguator: &dyn Display,
body: &Body<'tcx>,
mut extra_data: F,
extra_data: F,
options: PrettyPrintMirOptions,
) where
F: FnMut(PassWhere, &mut dyn io::Write) -> io::Result<()>,
{
let _: io::Result<()> = try {
let mut file = create_dump_file(tcx, "mir", pass_num, pass_name, disambiguator, body)?;
// see notes on #41697 above
let def_path =
ty::print::with_forced_impl_filename_line!(tcx.def_path_str(body.source.def_id()));
// ignore-tidy-odd-backticks the literal below is fine
write!(file, "// MIR for `{def_path}")?;
match body.source.promoted {
None => write!(file, "`")?,
Some(promoted) => write!(file, "::{promoted:?}`")?,
}
writeln!(file, " {disambiguator} {pass_name}")?;
if let Some(ref layout) = body.coroutine_layout_raw() {
writeln!(file, "/* coroutine_layout = {layout:#?} */")?;
}
writeln!(file)?;
extra_data(PassWhere::BeforeCFG, &mut file)?;
write_user_type_annotations(tcx, body, &mut file)?;
write_mir_fn(tcx, body, &mut extra_data, &mut file, options)?;
extra_data(PassWhere::AfterCFG, &mut file)?;
dump_mir_to_writer(tcx, pass_name, disambiguator, body, &mut file, extra_data, options)?;
};

if tcx.sess.opts.unstable_opts.dump_mir_graphviz {
Expand Down
6 changes: 4 additions & 2 deletions compiler/rustc_middle/src/mir/terminator.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -581,9 +581,11 @@ impl<'tcx> TerminatorKind<'tcx> {
pub enum TerminatorEdges<'mir, 'tcx> {
/// For terminators that have no successor, like `return`.
None,
/// For terminators that a single successor, like `goto`, and `assert` without cleanup block.
/// For terminators that have a single successor, like `goto`, and `assert` without a cleanup
/// block.
Single(BasicBlock),
/// For terminators that two successors, `assert` with cleanup block and `falseEdge`.
/// For terminators that have two successors, like `assert` with a cleanup block, and
/// `falseEdge`.
Double(BasicBlock, BasicBlock),
/// Special action for `Yield`, `Call` and `InlineAsm` terminators.
AssignOnReturn {
Expand Down

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