Auto merge of #6170 - ehuss:panic-in-unit, r=alexcrichton

Track `panic` in Unit early.

This is an alternate solution for #5445. It ensures that `panic` is cleared in the Profile for "for_host" targets (proc-macro/plugin/build-scripts) and dependencies. This helps avoid unnecessary recompiles in some situations (though does add extra units in some situations, see below).

Some examples where extra rebuilds are now avoided:
* A workspace with a dependency shared with normal and build-deps.  `build --all` should build everything, and then `build -p foo` was causing a recompile because the shared dep was no longer in the `used_in_plugin` set. Now it should not recompile.
* `panic=abort`, with a shared dependency in build and dev, `build` would cause that shared dependency to be built twice (exactly the same without panic set). Now it should only build once.

Some examples where `panic` is now set correctly:
* `panic=abort`, with a binary with a shared dependency in build and normal, `test` would cause that shared dependency to be built twice (exactly the same without panic set).  Now it is still built twice, but the one for the normal (bin) dependency will correctly have `panic` set.

Some examples where new units are now generated:
* `panic=abort`, with shared dependency between normal and proc-macro or build. Previously the shared dependency was built once with `panic=unwind`. Now it is built separately (once with `panic`, once without). I feel like that this is more correct behavior — that now the normal dependency avoids adding landing pads.

   For `panic=abort` cross-compiling, this makes no difference in compile time since it was already built twice.

Additional notes:
- I left build-scripts with the old behavior where `panic` is cleared for it and all its dependencies. There could be arguments made to change that (#5436), but it doesn't seem important to me.
- Renamed and refactored `ProfileFor` to `UnitFor`. I expect this API to continue to evolve in the future.

Closes #6143, closes #6154.

src/cargo/core/compiler/context/compilation_files.rs

@@ -427,7 +427,6 @@ fn compute_metadata<'a, 'cfg>(
     // panic=abort and panic=unwind artifacts, additionally with various
     // settings like debuginfo and whatnot.
     unit.profile.hash(&mut hasher);
-    cx.used_in_plugin.contains(unit).hash(&mut hasher);
     unit.mode.hash(&mut hasher);
     if let Some(ref args) = bcx.extra_args_for(unit) {
         args.hash(&mut hasher);

src/cargo/core/compiler/context/mod.rs

@@ -94,7 +94,6 @@ pub struct Context<'a, 'cfg: 'a> {
     pub compiled: HashSet<Unit<'a>>,
     pub build_scripts: HashMap<Unit<'a>, Arc<BuildScripts>>,
     pub links: Links<'a>,
-    pub used_in_plugin: HashSet<Unit<'a>>,
     pub jobserver: Client,
     primary_packages: HashSet<&'a PackageId>,
     unit_dependencies: HashMap<Unit<'a>, Vec<Unit<'a>>>,
@@ -127,7 +126,6 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
             build_scripts: HashMap::new(),
             build_explicit_deps: HashMap::new(),
             links: Links::new(),
-            used_in_plugin: HashSet::new(),
             jobserver,
             build_script_overridden: HashSet::new(),
 
@@ -334,7 +332,6 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
             &mut self.unit_dependencies,
             &mut self.package_cache,
         )?;
-        self.build_used_in_plugin_map(units)?;
         let files = CompilationFiles::new(
             units,
             host_layout,
@@ -371,37 +368,6 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
         Ok(())
     }
 
-    /// Builds up the `used_in_plugin` internal to this context from the list of
-    /// top-level units.
-    ///
-    /// This will recursively walk `units` and all of their dependencies to
-    /// determine which crate are going to be used in plugins or not.
-    fn build_used_in_plugin_map(&mut self, units: &[Unit<'a>]) -> CargoResult<()> {
-        let mut visited = HashSet::new();
-        for unit in units {
-            self.walk_used_in_plugin_map(unit, unit.target.for_host(), &mut visited)?;
-        }
-        Ok(())
-    }
-
-    fn walk_used_in_plugin_map(
-        &mut self,
-        unit: &Unit<'a>,
-        is_plugin: bool,
-        visited: &mut HashSet<(Unit<'a>, bool)>,
-    ) -> CargoResult<()> {
-        if !visited.insert((*unit, is_plugin)) {
-            return Ok(());
-        }
-        if is_plugin {
-            self.used_in_plugin.insert(*unit);
-        }
-        for unit in self.dep_targets(unit) {
-            self.walk_used_in_plugin_map(&unit, is_plugin || unit.target.for_host(), visited)?;
-        }
-        Ok(())
-    }
-
     pub fn files(&self) -> &CompilationFiles<'a, 'cfg> {
         self.files.as_ref().unwrap()
     }

src/cargo/core/compiler/context/unit_dependencies.rs

@@ -20,7 +20,7 @@ use std::collections::{HashMap, HashSet};
 
 use CargoResult;
 use core::dependency::Kind as DepKind;
-use core::profiles::ProfileFor;
+use core::profiles::UnitFor;
 use core::{Package, Target, PackageId};
 use core::package::Downloads;
 use super::{BuildContext, CompileMode, Kind, Unit};
@@ -59,12 +59,19 @@ pub fn build_unit_dependencies<'a, 'cfg>(
             // cleared, and avoid building the lib thrice (once with `panic`, once
             // without, once for --test).  In particular, the lib included for
             // doctests and examples are `Build` mode here.
-            let profile_for = if unit.mode.is_any_test() || bcx.build_config.test() {
-                ProfileFor::TestDependency
+            let unit_for = if unit.mode.is_any_test() || bcx.build_config.test() {
+                UnitFor::new_test()
+            } else if unit.target.is_custom_build() {
+                // This normally doesn't happen, except `clean` aggressively
+                // generates all units.
+                UnitFor::new_build()
+            } else if unit.target.for_host() {
+                // proc-macro/plugin should never have panic set.
+                UnitFor::new_compiler()
             } else {
-                ProfileFor::Any
+                UnitFor::new_normal()
             };
-            deps_of(unit, &mut state, profile_for)?;
+            deps_of(unit, &mut state, unit_for)?;
         }
 
         if state.waiting_on_download.len() > 0 {
@@ -84,34 +91,34 @@ pub fn build_unit_dependencies<'a, 'cfg>(
 fn deps_of<'a, 'cfg, 'tmp>(
     unit: &Unit<'a>,
     state: &mut State<'a, 'cfg, 'tmp>,
-    profile_for: ProfileFor,
+    unit_for: UnitFor,
 ) -> CargoResult<()> {
-    // Currently the `deps` map does not include `profile_for`.  This should
+    // Currently the `deps` map does not include `unit_for`.  This should
     // be safe for now.  `TestDependency` only exists to clear the `panic`
     // flag, and you'll never ask for a `unit` with `panic` set as a
     // `TestDependency`.  `CustomBuild` should also be fine since if the
     // requested unit's settings are the same as `Any`, `CustomBuild` can't
     // affect anything else in the hierarchy.
     if !state.deps.contains_key(unit) {
-        let unit_deps = compute_deps(unit, state, profile_for)?;
+        let unit_deps = compute_deps(unit, state, unit_for)?;
         let to_insert: Vec<_> = unit_deps.iter().map(|&(unit, _)| unit).collect();
         state.deps.insert(*unit, to_insert);
-        for (unit, profile_for) in unit_deps {
-            deps_of(&unit, state, profile_for)?;
+        for (unit, unit_for) in unit_deps {
+            deps_of(&unit, state, unit_for)?;
         }
     }
     Ok(())
 }
 
 /// For a package, return all targets which are registered as dependencies
 /// for that package.
-/// This returns a vec of `(Unit, ProfileFor)` pairs.  The `ProfileFor`
+/// This returns a vec of `(Unit, UnitFor)` pairs.  The `UnitFor`
 /// is the profile type that should be used for dependencies of the unit.
 fn compute_deps<'a, 'cfg, 'tmp>(
     unit: &Unit<'a>,
     state: &mut State<'a, 'cfg, 'tmp>,
-    profile_for: ProfileFor,
-) -> CargoResult<Vec<(Unit<'a>, ProfileFor)>> {
+    unit_for: UnitFor,
+) -> CargoResult<Vec<(Unit<'a>, UnitFor)>> {
     if unit.mode.is_run_custom_build() {
         return compute_deps_custom_build(unit, state.bcx);
     } else if unit.mode.is_doc() && !unit.mode.is_any_test() {
@@ -173,15 +180,16 @@ fn compute_deps<'a, 'cfg, 'tmp>(
             None => continue,
         };
         let mode = check_or_build_mode(unit.mode, lib);
+        let dep_unit_for = unit_for.with_for_host(lib.for_host());
         let unit = new_unit(
             bcx,
             pkg,
             lib,
-            profile_for,
+            dep_unit_for,
             unit.kind.for_target(lib),
             mode,
         );
-        ret.push((unit, profile_for));
+        ret.push((unit, dep_unit_for));
     }
 
     // If this target is a build script, then what we've collected so far is
@@ -199,7 +207,7 @@ fn compute_deps<'a, 'cfg, 'tmp>(
     if unit.target.is_lib() && unit.mode != CompileMode::Doctest {
         return Ok(ret);
     }
-    ret.extend(maybe_lib(unit, bcx, profile_for));
+    ret.extend(maybe_lib(unit, bcx, unit_for));
 
     // If any integration tests/benches are being run, make sure that
     // binaries are built as well.
@@ -225,11 +233,11 @@ fn compute_deps<'a, 'cfg, 'tmp>(
                             bcx,
                             unit.pkg,
                             t,
-                            ProfileFor::Any,
+                            UnitFor::new_normal(),
                             unit.kind.for_target(t),
                             CompileMode::Build,
                         ),
-                        ProfileFor::Any,
+                        UnitFor::new_normal(),
                     )
                 }),
         );
@@ -245,7 +253,7 @@ fn compute_deps<'a, 'cfg, 'tmp>(
 fn compute_deps_custom_build<'a, 'cfg>(
     unit: &Unit<'a>,
     bcx: &BuildContext<'a, 'cfg>,
-) -> CargoResult<Vec<(Unit<'a>, ProfileFor)>> {
+) -> CargoResult<Vec<(Unit<'a>, UnitFor)>> {
     // When not overridden, then the dependencies to run a build script are:
     //
     // 1. Compiling the build script itself
@@ -259,20 +267,20 @@ fn compute_deps_custom_build<'a, 'cfg>(
         bcx,
         unit.pkg,
         unit.target,
-        ProfileFor::CustomBuild,
+        UnitFor::new_build(),
         Kind::Host, // build scripts always compiled for the host
         CompileMode::Build,
     );
     // All dependencies of this unit should use profiles for custom
     // builds.
-    Ok(vec![(unit, ProfileFor::CustomBuild)])
+    Ok(vec![(unit, UnitFor::new_build())])
 }
 
 /// Returns the dependencies necessary to document a package
 fn compute_deps_doc<'a, 'cfg, 'tmp>(
     unit: &Unit<'a>,
     state: &mut State<'a, 'cfg, 'tmp>,
-) -> CargoResult<Vec<(Unit<'a>, ProfileFor)>> {
+) -> CargoResult<Vec<(Unit<'a>, UnitFor)>> {
     let bcx = state.bcx;
     let deps = bcx.resolve
         .deps(unit.pkg.package_id())
@@ -299,26 +307,27 @@ fn compute_deps_doc<'a, 'cfg, 'tmp>(
         // rustdoc only needs rmeta files for regular dependencies.
         // However, for plugins/proc-macros, deps should be built like normal.
         let mode = check_or_build_mode(unit.mode, lib);
+        let dep_unit_for = UnitFor::new_normal().with_for_host(lib.for_host());
         let lib_unit = new_unit(
             bcx,
             dep,
             lib,
-            ProfileFor::Any,
+            dep_unit_for,
             unit.kind.for_target(lib),
             mode,
         );
-        ret.push((lib_unit, ProfileFor::Any));
+        ret.push((lib_unit, dep_unit_for));
         if let CompileMode::Doc { deps: true } = unit.mode {
             // Document this lib as well.
             let doc_unit = new_unit(
                 bcx,
                 dep,
                 lib,
-                ProfileFor::Any,
+                dep_unit_for,
                 unit.kind.for_target(lib),
                 unit.mode,
             );
-            ret.push((doc_unit, ProfileFor::Any));
+            ret.push((doc_unit, dep_unit_for));
         }
     }
 
@@ -327,27 +336,27 @@ fn compute_deps_doc<'a, 'cfg, 'tmp>(
 
     // If we document a binary, we need the library available
     if unit.target.is_bin() {
-        ret.extend(maybe_lib(unit, bcx, ProfileFor::Any));
+        ret.extend(maybe_lib(unit, bcx, UnitFor::new_normal()));
     }
     Ok(ret)
 }
 
 fn maybe_lib<'a>(
     unit: &Unit<'a>,
     bcx: &BuildContext,
-    profile_for: ProfileFor,
-) -> Option<(Unit<'a>, ProfileFor)> {
+    unit_for: UnitFor,
+) -> Option<(Unit<'a>, UnitFor)> {
     unit.pkg.targets().iter().find(|t| t.linkable()).map(|t| {
         let mode = check_or_build_mode(unit.mode, t);
         let unit = new_unit(
             bcx,
             unit.pkg,
             t,
-            profile_for,
+            unit_for,
             unit.kind.for_target(t),
             mode,
         );
-        (unit, profile_for)
+        (unit, unit_for)
     })
 }
 
@@ -358,7 +367,7 @@ fn maybe_lib<'a>(
 /// script itself doesn't have any dependencies, so even in that case a unit
 /// of work is still returned. `None` is only returned if the package has no
 /// build script.
-fn dep_build_script<'a>(unit: &Unit<'a>, bcx: &BuildContext) -> Option<(Unit<'a>, ProfileFor)> {
+fn dep_build_script<'a>(unit: &Unit<'a>, bcx: &BuildContext) -> Option<(Unit<'a>, UnitFor)> {
     unit.pkg
         .targets()
         .iter()
@@ -374,7 +383,7 @@ fn dep_build_script<'a>(unit: &Unit<'a>, bcx: &BuildContext) -> Option<(Unit<'a>
                     kind: unit.kind,
                     mode: CompileMode::RunCustomBuild,
                 },
-                ProfileFor::CustomBuild,
+                UnitFor::new_build(),
             )
         })
 }
@@ -401,14 +410,14 @@ fn new_unit<'a>(
     bcx: &BuildContext,
     pkg: &'a Package,
     target: &'a Target,
-    profile_for: ProfileFor,
+    unit_for: UnitFor,
     kind: Kind,
     mode: CompileMode,
 ) -> Unit<'a> {
     let profile = bcx.profiles.get_profile(
         &pkg.package_id(),
         bcx.ws.is_member(pkg),
-        profile_for,
+        unit_for,
         mode,
         bcx.build_config.release,
     );

src/cargo/core/compiler/fingerprint.rs

@@ -466,7 +466,6 @@ fn calculate<'a, 'cfg>(
         unit.mode,
         bcx.extra_args_for(unit),
         cx.incremental_args(unit)?,
-        cx.used_in_plugin.contains(unit), // used when passing panic=abort
     ));
     let fingerprint = Arc::new(Fingerprint {
         rustc: util::hash_u64(&bcx.rustc.verbose_version),

src/cargo/core/compiler/mod.rs

@@ -765,20 +765,8 @@ fn build_base_args<'a, 'cfg>(
         cmd.arg("-C").arg(&format!("opt-level={}", opt_level));
     }
 
-    // If a panic mode was configured *and* we're not ever going to be used in a
-    // plugin, then we can compile with that panic mode.
-    //
-    // If we're used in a plugin then we'll eventually be linked to libsyntax
-    // most likely which isn't compiled with a custom panic mode, so we'll just
-    // get an error if we actually compile with that. This fixes `panic=abort`
-    // crates which have plugin dependencies, but unfortunately means that
-    // dependencies shared between the main application and plugins must be
-    // compiled without `panic=abort`. This isn't so bad, though, as the main
-    // application will still be compiled with `panic=abort`.
     if let Some(panic) = panic.as_ref() {
-        if !cx.used_in_plugin.contains(unit) {
-            cmd.arg("-C").arg(format!("panic={}", panic));
-        }
+        cmd.arg("-C").arg(format!("panic={}", panic));
     }
 
     // Disable LTO for host builds as prefer_dynamic and it are mutually