Introduce `MirDumper` and `MirWriter`.

MIR dumping is a mess. There are lots of functions and entry points,
e.g. `dump_mir`, `dump_mir_with_options`, `dump_polonius_mir`,
`dump_mir_to_writer`. Also, it's crucial that `create_dump_file` is
never called without `dump_enabled` first being checked, but there is no
mechanism for ensuring this and it's hard to tell if it is satisfied on
all paths. (`dump_enabled` is checked twice on some paths, however!)

This commit introduces `MirWriter`, which controls the MIR writing, and
encapsulates the `extra_data` closure and `options`. Two existing
functions are now methods of this type. It sets reasonable defaults,
allowing the removal of many `|_, _| Ok(())` closures.

The commit also introduces `MirDumper`, which is layered on top of
`MirWriter`, and which manages the creation of the dump files,
encapsulating pass names, disambiguators, etc. Four existing functions
are now methods of this type.
- `MirDumper::new` will only succeed if dumps are enabled, and will
  return `None` otherwise, which makes it impossible to dump when you
  shouldn't.
- It also sets reasonable defaults for various things like
  disambiguators, which means you no longer need to specify them in many
  cases. When they do need to be specified, it's now done via setter
  methods.
- It avoids some repetition. E.g. `dump_nll_mir` previously specifed the
  pass name `"nll"` four times and the disambiguator `&0` three times;
  now it specifies them just once, to put them in the `MirDumper`.
- For Polonius, the `extra_data` closure can now be specified earlier,
  which avoids having to pass some arguments through some functions.

7 files changed, 70 insertions, 37 deletions

diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index 592192944d2..4603c695ded 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -1294,7 +1294,9 @@ fn create_coroutine_resume_function<'tcx>(
 
     pm::run_passes_no_validate(tcx, body, &[&abort_unwinding_calls::AbortUnwindingCalls], None);
 
-    dump_mir(tcx, false, "coroutine_resume", &0, body, &|_, _| Ok(()));
+    if let Some(dumper) = MirDumper::new(tcx, "coroutine_resume", body) {
+        dumper.dump_mir(body);
+    }
 }
 
 /// An operation that can be performed on a coroutine.
@@ -1446,7 +1448,9 @@ impl<'tcx> crate::MirPass<'tcx> for StateTransform {
 
         assert!(body.coroutine_drop().is_none() && body.coroutine_drop_async().is_none());
 
-        dump_mir(tcx, false, "coroutine_before", &0, body, &|_, _| Ok(()));
+        if let Some(dumper) = MirDumper::new(tcx, "coroutine_before", body) {
+            dumper.dump_mir(body);
+        }
 
         // The first argument is the coroutine type passed by value
         let coroutine_ty = body.local_decls.raw[1].ty;
@@ -1506,7 +1510,10 @@ impl<'tcx> crate::MirPass<'tcx> for StateTransform {
         ) {
             let context_mut_ref = transform_async_context(tcx, body);
             expand_async_drops(tcx, body, context_mut_ref, coroutine_kind, coroutine_ty);
-            dump_mir(tcx, false, "coroutine_async_drop_expand", &0, body, &|_, _| Ok(()));
+
+            if let Some(dumper) = MirDumper::new(tcx, "coroutine_async_drop_expand", body) {
+                dumper.dump_mir(body);
+            }
         } else {
             cleanup_async_drops(body);
         }
@@ -1605,14 +1612,18 @@ impl<'tcx> crate::MirPass<'tcx> for StateTransform {
         // This is expanded to a drop ladder in `elaborate_coroutine_drops`.
         let drop_clean = insert_clean_drop(tcx, body, has_async_drops);
 
-        dump_mir(tcx, false, "coroutine_pre-elab", &0, body, &|_, _| Ok(()));
+        if let Some(dumper) = MirDumper::new(tcx, "coroutine_pre-elab", body) {
+            dumper.dump_mir(body);
+        }
 
         // Expand `drop(coroutine_struct)` to a drop ladder which destroys upvars.
         // If any upvars are moved out of, drop elaboration will handle upvar destruction.
         // However we need to also elaborate the code generated by `insert_clean_drop`.
         elaborate_coroutine_drops(tcx, body);
 
-        dump_mir(tcx, false, "coroutine_post-transform", &0, body, &|_, _| Ok(()));
+        if let Some(dumper) = MirDumper::new(tcx, "coroutine_post-transform", body) {
+            dumper.dump_mir(body);
+        }
 
         let can_unwind = can_unwind(tcx, body);
 
diff --git a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
index 5ba6fea9faf..951ff69c19e 100644
--- a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
+++ b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
@@ -77,7 +77,7 @@ use rustc_hir::definitions::DisambiguatorState;
 use rustc_middle::bug;
 use rustc_middle::hir::place::{Projection, ProjectionKind};
 use rustc_middle::mir::visit::MutVisitor;
-use rustc_middle::mir::{self, dump_mir};
+use rustc_middle::mir::{self, MirDumper};
 use rustc_middle::ty::{self, InstanceKind, Ty, TyCtxt, TypeVisitableExt};
 
 pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
@@ -225,7 +225,10 @@ pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
     );
     by_move_body.source =
         mir::MirSource::from_instance(InstanceKind::Item(body_def.def_id().to_def_id()));
-    dump_mir(tcx, false, "built", &"after", &by_move_body, &|_, _| Ok(()));
+
+    if let Some(dumper) = MirDumper::new(tcx, "built", &by_move_body) {
+        dumper.set_disambiguator(&"after").dump_mir(&by_move_body);
+    }
 
     // Feed HIR because we try to access this body's attrs in the inliner.
     body_def.feed_hir();
diff --git a/compiler/rustc_mir_transform/src/coroutine/drop.rs b/compiler/rustc_mir_transform/src/coroutine/drop.rs
index 6dffbc86627..fd2d8b2b056 100644
--- a/compiler/rustc_mir_transform/src/coroutine/drop.rs
+++ b/compiler/rustc_mir_transform/src/coroutine/drop.rs
@@ -605,7 +605,9 @@ pub(super) fn create_coroutine_drop_shim<'tcx>(
     // Temporary change MirSource to coroutine's instance so that dump_mir produces more sensible
     // filename.
     body.source.instance = coroutine_instance;
-    dump_mir(tcx, false, "coroutine_drop", &0, &body, &|_, _| Ok(()));
+    if let Some(dumper) = MirDumper::new(tcx, "coroutine_drop", &body) {
+        dumper.dump_mir(&body);
+    }
     body.source.instance = drop_instance;
 
     // Creating a coroutine drop shim happens on `Analysis(PostCleanup) -> Runtime(Initial)`
@@ -696,7 +698,9 @@ pub(super) fn create_coroutine_drop_shim_async<'tcx>(
         None,
     );
 
-    dump_mir(tcx, false, "coroutine_drop_async", &0, &body, &|_, _| Ok(()));
+    if let Some(dumper) = MirDumper::new(tcx, "coroutine_drop_async", &body) {
+        dumper.dump_mir(&body);
+    }
 
     body
 }
@@ -741,7 +745,9 @@ pub(super) fn create_coroutine_drop_shim_proxy_async<'tcx>(
     };
     body.basic_blocks_mut()[call_bb].terminator = Some(Terminator { source_info, kind });
 
-    dump_mir(tcx, false, "coroutine_drop_proxy_async", &0, &body, &|_, _| Ok(()));
+    if let Some(dumper) = MirDumper::new(tcx, "coroutine_drop_proxy_async", &body) {
+        dumper.dump_mir(&body);
+    }
 
     body
 }
diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs
index bb68d1a0659..cf7425251e8 100644
--- a/compiler/rustc_mir_transform/src/dest_prop.rs
+++ b/compiler/rustc_mir_transform/src/dest_prop.rs
@@ -137,8 +137,8 @@ use rustc_index::interval::SparseIntervalMatrix;
 use rustc_middle::bug;
 use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
 use rustc_middle::mir::{
-    Body, HasLocalDecls, InlineAsmOperand, Local, LocalKind, Location, Operand, PassWhere, Place,
-    Rvalue, Statement, StatementKind, TerminatorKind, dump_mir, traversal,
+    Body, HasLocalDecls, InlineAsmOperand, Local, LocalKind, Location, MirDumper, Operand,
+    PassWhere, Place, Rvalue, Statement, StatementKind, TerminatorKind, traversal,
 };
 use rustc_middle::ty::TyCtxt;
 use rustc_mir_dataflow::Analysis;
@@ -810,11 +810,15 @@ fn dest_prop_mir_dump<'tcx>(
         let location = points.point_from_location(location);
         live.rows().filter(|&r| live.contains(r, location)).collect::<Vec<_>>()
     };
-    dump_mir(tcx, false, "DestinationPropagation-dataflow", &round, body, &|pass_where, w| {
-        if let PassWhere::BeforeLocation(loc) = pass_where {
-            writeln!(w, "        // live: {:?}", locals_live_at(loc))?;
-        }
 
-        Ok(())
-    });
+    if let Some(dumper) = MirDumper::new(tcx, "DestinationPropagation-dataflow", body) {
+        let extra_data = &|pass_where, w: &mut dyn std::io::Write| {
+            if let PassWhere::BeforeLocation(loc) = pass_where {
+                writeln!(w, "        // live: {:?}", locals_live_at(loc))?;
+            }
+            Ok(())
+        };
+
+        dumper.set_disambiguator(&round).set_extra_data(extra_data).dump_mir(body)
+    }
 }
diff --git a/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs b/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
index 0d0a71bc6c7..794984d2f3e 100644
--- a/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
+++ b/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
@@ -12,8 +12,8 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
 use rustc_middle::bug;
 use rustc_middle::mir::{
-    self, BasicBlock, Body, ClearCrossCrate, Local, Location, Place, StatementKind, TerminatorKind,
-    dump_mir,
+    self, BasicBlock, Body, ClearCrossCrate, Local, Location, MirDumper, Place, StatementKind,
+    TerminatorKind,
 };
 use rustc_middle::ty::significant_drop_order::{
     extract_component_with_significant_dtor, ty_dtor_span,
@@ -227,7 +227,10 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
         return;
     }
 
-    dump_mir(tcx, false, "lint_tail_expr_drop_order", &0 as _, body, &|_, _| Ok(()));
+    if let Some(dumper) = MirDumper::new(tcx, "lint_tail_expr_drop_order", body) {
+        dumper.dump_mir(body);
+    }
+
     let locals_with_user_names = collect_user_names(body);
     let is_closure_like = tcx.is_closure_like(def_id.to_def_id());
 
diff --git a/compiler/rustc_mir_transform/src/pass_manager.rs b/compiler/rustc_mir_transform/src/pass_manager.rs
index 374623d4ea5..ab09cdf787e 100644
--- a/compiler/rustc_mir_transform/src/pass_manager.rs
+++ b/compiler/rustc_mir_transform/src/pass_manager.rs
@@ -2,7 +2,7 @@ use std::cell::RefCell;
 use std::collections::hash_map::Entry;
 
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
-use rustc_middle::mir::{self, Body, MirPhase, RuntimePhase};
+use rustc_middle::mir::{Body, MirDumper, MirPhase, RuntimePhase};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use tracing::trace;
@@ -275,7 +275,6 @@ fn run_passes_inner<'tcx>(
     }
 
     let prof_arg = tcx.sess.prof.enabled().then(|| format!("{:?}", body.source.def_id()));
-    let pass_num = true;
 
     if !body.should_skip() {
         let validate = validate_each & tcx.sess.opts.unstable_opts.validate_mir;
@@ -288,10 +287,16 @@ fn run_passes_inner<'tcx>(
                 continue;
             };
 
-            let dump_enabled = pass.is_mir_dump_enabled();
+            let dumper = if pass.is_mir_dump_enabled()
+                && let Some(dumper) = MirDumper::new(tcx, pass_name, body)
+            {
+                Some(dumper.set_show_pass_num().set_disambiguator(&"before"))
+            } else {
+                None
+            };
 
-            if dump_enabled {
-                mir::dump_mir(tcx, pass_num, pass_name, &"before", body, &|_, _| Ok(()));
+            if let Some(dumper) = dumper.as_ref() {
+                dumper.dump_mir(body);
             }
 
             if let Some(prof_arg) = &prof_arg {
@@ -303,9 +308,10 @@ fn run_passes_inner<'tcx>(
                 pass.run_pass(tcx, body);
             }
 
-            if dump_enabled {
-                mir::dump_mir(tcx, pass_num, pass_name, &"after", body, &|_, _| Ok(()));
+            if let Some(dumper) = dumper {
+                dumper.set_disambiguator(&"after").dump_mir(body);
             }
+
             if validate {
                 validate_body(tcx, body, format!("after pass {pass_name}"));
             }
@@ -348,5 +354,7 @@ pub(super) fn validate_body<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, when
 
 pub(super) fn dump_mir_for_phase_change<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
     assert_eq!(body.pass_count, 0);
-    mir::dump_mir(tcx, true, body.phase.name(), &"after", body, &|_, _| Ok(()))
+    if let Some(dumper) = MirDumper::new(tcx, body.phase.name(), body) {
+        dumper.set_show_pass_num().set_disambiguator(&"after").dump_mir(body)
+    }
 }
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index 39d4aaa9857..bca8ffb693b 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -1242,14 +1242,12 @@ fn build_construct_coroutine_by_move_shim<'tcx>(
 
     let body =
         new_body(source, IndexVec::from_elem_n(start_block, 1), locals, sig.inputs().len(), span);
-    dump_mir(
-        tcx,
-        false,
-        if receiver_by_ref { "coroutine_closure_by_ref" } else { "coroutine_closure_by_move" },
-        &0,
-        &body,
-        &|_, _| Ok(()),
-    );
+
+    let pass_name =
+        if receiver_by_ref { "coroutine_closure_by_ref" } else { "coroutine_closure_by_move" };
+    if let Some(dumper) = MirDumper::new(tcx, pass_name, &body) {
+        dumper.dump_mir(&body);
+    }
 
     body
 }