Auto merge of #105121 - oli-obk:simpler-cheaper-dump_mir, r=nnethercote

Cheaper `dump_mir` take two

alternative to #105083

r? `@nnethercote`

compiler/rustc_mir_transform/src/coverage/debug.rs

@@ -638,7 +638,7 @@ pub(super) fn dump_coverage_spanview<'tcx>(
     let def_id = mir_source.def_id();
 
     let span_viewables = span_viewables(tcx, mir_body, basic_coverage_blocks, &coverage_spans);
-    let mut file = create_dump_file(tcx, "html", None, pass_name, &0, mir_source)
+    let mut file = create_dump_file(tcx, "html", false, pass_name, &0, mir_body)
         .expect("Unexpected error creating MIR spanview HTML file");
     let crate_name = tcx.crate_name(def_id.krate);
     let item_name = tcx.def_path(def_id).to_filename_friendly_no_crate();
@@ -739,7 +739,7 @@ pub(super) fn dump_coverage_graphviz<'tcx>(
                 .join("\n  ")
         ));
     }
-    let mut file = create_dump_file(tcx, "dot", None, pass_name, &0, mir_source)
+    let mut file = create_dump_file(tcx, "dot", false, pass_name, &0, mir_body)
         .expect("Unexpected error creating BasicCoverageBlock graphviz DOT file");
     graphviz_writer
         .write_graphviz(tcx, &mut file)

compiler/rustc_mir_transform/src/dest_prop.rs

@@ -787,7 +787,7 @@ fn dest_prop_mir_dump<'body, 'tcx>(
     round: usize,
 ) {
     let mut reachable = None;
-    dump_mir(tcx, None, "DestinationPropagation-dataflow", &round, body, |pass_where, w| {
+    dump_mir(tcx, false, "DestinationPropagation-dataflow", &round, body, |pass_where, w| {
         let reachable = reachable.get_or_insert_with(|| traversal::reachable_as_bitset(body));
 
         match pass_where {

compiler/rustc_mir_transform/src/dump_mir.rs

@@ -1,6 +1,5 @@
 //! This pass just dumps MIR at a specified point.
 
-use std::borrow::Cow;
 use std::fs::File;
 use std::io;
 
@@ -13,8 +12,8 @@ use rustc_session::config::{OutputFilenames, OutputType};
 pub struct Marker(pub &'static str);
 
 impl<'tcx> MirPass<'tcx> for Marker {
-    fn name(&self) -> Cow<'_, str> {
-        Cow::Borrowed(self.0)
+    fn name(&self) -> &str {
+        self.0
     }
 
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, _body: &mut Body<'tcx>) {}

compiler/rustc_mir_transform/src/generator.rs

@@ -1000,7 +1000,7 @@ fn create_generator_drop_shim<'tcx>(
     // unrelated code from the resume part of the function
     simplify::remove_dead_blocks(tcx, &mut body);
 
-    dump_mir(tcx, None, "generator_drop", &0, &body, |_, _| Ok(()));
+    dump_mir(tcx, false, "generator_drop", &0, &body, |_, _| Ok(()));
 
     body
 }
@@ -1171,7 +1171,7 @@ fn create_generator_resume_function<'tcx>(
     // unrelated code from the drop part of the function
     simplify::remove_dead_blocks(tcx, body);
 
-    dump_mir(tcx, None, "generator_resume", &0, body, |_, _| Ok(()));
+    dump_mir(tcx, false, "generator_resume", &0, body, |_, _| Ok(()));
 }
 
 fn insert_clean_drop(body: &mut Body<'_>) -> BasicBlock {
@@ -1394,14 +1394,14 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         // This is expanded to a drop ladder in `elaborate_generator_drops`.
         let drop_clean = insert_clean_drop(body);
 
-        dump_mir(tcx, None, "generator_pre-elab", &0, body, |_, _| Ok(()));
+        dump_mir(tcx, false, "generator_pre-elab", &0, body, |_, _| Ok(()));
 
         // Expand `drop(generator_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_generator_drops(tcx, body);
 
-        dump_mir(tcx, None, "generator_post-transform", &0, body, |_, _| Ok(()));
+        dump_mir(tcx, false, "generator_post-transform", &0, body, |_, _| Ok(()));
 
         // Create a copy of our MIR and use it to create the drop shim for the generator
         let drop_shim = create_generator_drop_shim(tcx, &transform, gen_ty, body, drop_clean);

compiler/rustc_mir_transform/src/pass_manager.rs

@@ -1,5 +1,3 @@
-use std::borrow::Cow;
-
 use rustc_middle::mir::{self, Body, MirPhase, RuntimePhase};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
@@ -8,13 +6,9 @@ use crate::{validate, MirPass};
 
 /// Just like `MirPass`, except it cannot mutate `Body`.
 pub trait MirLint<'tcx> {
-    fn name(&self) -> Cow<'_, str> {
+    fn name(&self) -> &str {
         let name = std::any::type_name::<Self>();
-        if let Some(tail) = name.rfind(':') {
-            Cow::from(&name[tail + 1..])
-        } else {
-            Cow::from(name)
-        }
+        if let Some((_, tail)) = name.rsplit_once(':') { tail } else { name }
     }
 
     fn is_enabled(&self, _sess: &Session) -> bool {
@@ -32,7 +26,7 @@ impl<'tcx, T> MirPass<'tcx> for Lint<T>
 where
     T: MirLint<'tcx>,
 {
-    fn name(&self) -> Cow<'_, str> {
+    fn name(&self) -> &str {
         self.0.name()
     }
 
@@ -55,7 +49,7 @@ impl<'tcx, T> MirPass<'tcx> for WithMinOptLevel<T>
 where
     T: MirPass<'tcx>,
 {
-    fn name(&self) -> Cow<'_, str> {
+    fn name(&self) -> &str {
         self.1.name()
     }
 
@@ -146,10 +140,11 @@ fn run_passes_inner<'tcx>(
         }
 
         body.phase = new_phase;
+        body.pass_count = 0;
 
         dump_mir_for_phase_change(tcx, body);
         if validate || new_phase == MirPhase::Runtime(RuntimePhase::Optimized) {
-            validate_body(tcx, body, format!("after phase change to {}", new_phase));
+            validate_body(tcx, body, format!("after phase change to {}", new_phase.name()));
         }
 
         body.pass_count = 1;
@@ -166,11 +161,9 @@ pub fn dump_mir_for_pass<'tcx>(
     pass_name: &str,
     is_after: bool,
 ) {
-    let phase_index = body.phase.phase_index();
-
     mir::dump_mir(
         tcx,
-        Some(&format_args!("{:03}-{:03}", phase_index, body.pass_count)),
+        true,
         pass_name,
         if is_after { &"after" } else { &"before" },
         body,
@@ -179,14 +172,6 @@ pub fn dump_mir_for_pass<'tcx>(
 }
 
 pub fn dump_mir_for_phase_change<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
-    let phase_index = body.phase.phase_index();
-
-    mir::dump_mir(
-        tcx,
-        Some(&format_args!("{:03}-000", phase_index)),
-        &format!("{}", body.phase),
-        &"after",
-        body,
-        |_, _| Ok(()),
-    )
+    assert_eq!(body.pass_count, 0);
+    mir::dump_mir(tcx, true, body.phase.name(), &"after", body, |_, _| Ok(()))
 }

compiler/rustc_mir_transform/src/simplify.rs

@@ -35,7 +35,6 @@ use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Vis
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use smallvec::SmallVec;
-use std::borrow::Cow;
 use std::convert::TryInto;
 
 pub struct SimplifyCfg {
@@ -57,8 +56,8 @@ pub fn simplify_cfg<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 }
 
 impl<'tcx> MirPass<'tcx> for SimplifyCfg {
-    fn name(&self) -> Cow<'_, str> {
-        Cow::Borrowed(&self.label)
+    fn name(&self) -> &str {
+        &self.label
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {

compiler/rustc_mir_transform/src/simplify_branches.rs

@@ -2,8 +2,6 @@ use crate::MirPass;
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 
-use std::borrow::Cow;
-
 /// A pass that replaces a branch with a goto when its condition is known.
 pub struct SimplifyConstCondition {
     label: String,
@@ -16,8 +14,8 @@ impl SimplifyConstCondition {
 }
 
 impl<'tcx> MirPass<'tcx> for SimplifyConstCondition {
-    fn name(&self) -> Cow<'_, str> {
-        Cow::Borrowed(&self.label)
+    fn name(&self) -> &str {
+        &self.label
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {