Auto merge of #84233 - jyn514:track-path-prefix, r=michaelwoerister

Add TRACKED_NO_CRATE_HASH and use it for `--remap-path-prefix`

I verified locally that this fixes https://github.com/rust-lang/rust/issues/66955.

r? `@Aaron1011` (feel free to reassign)

10 files changed, 251 insertions, 184 deletions

diff --git a/compiler/rustc_incremental/src/persist/load.rs b/compiler/rustc_incremental/src/persist/load.rs
index 259e540c612..2661afd7ffc 100644
--- a/compiler/rustc_incremental/src/persist/load.rs
+++ b/compiler/rustc_incremental/src/persist/load.rs
@@ -104,7 +104,7 @@ pub fn load_dep_graph(sess: &Session) -> DepGraphFuture {
     // Fortunately, we just checked that this isn't the case.
     let path = dep_graph_path_from(&sess.incr_comp_session_dir());
     let report_incremental_info = sess.opts.debugging_opts.incremental_info;
-    let expected_hash = sess.opts.dep_tracking_hash();
+    let expected_hash = sess.opts.dep_tracking_hash(false);
 
     let mut prev_work_products = FxHashMap::default();
     let nightly_build = sess.is_nightly_build();
diff --git a/compiler/rustc_incremental/src/persist/save.rs b/compiler/rustc_incremental/src/persist/save.rs
index d558af3c1d5..1484088837a 100644
--- a/compiler/rustc_incremental/src/persist/save.rs
+++ b/compiler/rustc_incremental/src/persist/save.rs
@@ -219,7 +219,7 @@ pub fn build_dep_graph(
     }
 
     // First encode the commandline arguments hash
-    if let Err(err) = sess.opts.dep_tracking_hash().encode(&mut encoder) {
+    if let Err(err) = sess.opts.dep_tracking_hash(false).encode(&mut encoder) {
         sess.err(&format!(
             "failed to write dependency graph hash `{}`: {}",
             path_buf.display(),
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 9685d21762b..d8c1a7a2682 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -19,6 +19,7 @@ use rustc_span::symbol::sym;
 use rustc_span::SourceFileHashAlgorithm;
 use rustc_target::spec::{CodeModel, LinkerFlavor, MergeFunctions, PanicStrategy};
 use rustc_target::spec::{RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo, TlsModel};
+
 use std::collections::{BTreeMap, BTreeSet};
 use std::iter::FromIterator;
 use std::num::NonZeroUsize;
@@ -74,6 +75,27 @@ fn mk_map<K: Ord, V>(entries: Vec<(K, V)>) -> BTreeMap<K, V> {
     BTreeMap::from_iter(entries.into_iter())
 }
 
+fn assert_same_clone(x: &Options) {
+    assert_eq!(x.dep_tracking_hash(true), x.clone().dep_tracking_hash(true));
+    assert_eq!(x.dep_tracking_hash(false), x.clone().dep_tracking_hash(false));
+}
+
+fn assert_same_hash(x: &Options, y: &Options) {
+    assert_eq!(x.dep_tracking_hash(true), y.dep_tracking_hash(true));
+    assert_eq!(x.dep_tracking_hash(false), y.dep_tracking_hash(false));
+    // Check clone
+    assert_same_clone(x);
+    assert_same_clone(y);
+}
+
+fn assert_different_hash(x: &Options, y: &Options) {
+    assert_ne!(x.dep_tracking_hash(true), y.dep_tracking_hash(true));
+    assert_ne!(x.dep_tracking_hash(false), y.dep_tracking_hash(false));
+    // Check clone
+    assert_same_clone(x);
+    assert_same_clone(y);
+}
+
 // When the user supplies --test we should implicitly supply --cfg test
 #[test]
 fn test_switch_implies_cfg_test() {
@@ -130,14 +152,9 @@ fn test_output_types_tracking_hash_different_paths() {
     v2.output_types = OutputTypes::new(&[(OutputType::Exe, Some(PathBuf::from("/some/thing")))]);
     v3.output_types = OutputTypes::new(&[(OutputType::Exe, None)]);
 
-    assert!(v1.dep_tracking_hash() != v2.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() != v3.dep_tracking_hash());
-    assert!(v2.dep_tracking_hash() != v3.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
-    assert_eq!(v3.dep_tracking_hash(), v3.clone().dep_tracking_hash());
+    assert_different_hash(&v1, &v2);
+    assert_different_hash(&v1, &v3);
+    assert_different_hash(&v2, &v3);
 }
 
 #[test]
@@ -155,10 +172,7 @@ fn test_output_types_tracking_hash_different_construction_order() {
         (OutputType::Exe, Some(PathBuf::from("./some/thing"))),
     ]);
 
-    assert_eq!(v1.dep_tracking_hash(), v2.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
+    assert_same_hash(&v1, &v2);
 }
 
 #[test]
@@ -182,14 +196,9 @@ fn test_externs_tracking_hash_different_construction_order() {
         (String::from("d"), new_public_extern_entry(vec!["f", "e"])),
     ]));
 
-    assert_eq!(v1.dep_tracking_hash(), v2.dep_tracking_hash());
-    assert_eq!(v1.dep_tracking_hash(), v3.dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v3.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
-    assert_eq!(v3.dep_tracking_hash(), v3.clone().dep_tracking_hash());
+    assert_same_hash(&v1, &v2);
+    assert_same_hash(&v1, &v3);
+    assert_same_hash(&v2, &v3);
 }
 
 #[test]
@@ -219,14 +228,9 @@ fn test_lints_tracking_hash_different_values() {
         (String::from("d"), Level::Deny),
     ];
 
-    assert!(v1.dep_tracking_hash() != v2.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() != v3.dep_tracking_hash());
-    assert!(v2.dep_tracking_hash() != v3.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
-    assert_eq!(v3.dep_tracking_hash(), v3.clone().dep_tracking_hash());
+    assert_different_hash(&v1, &v2);
+    assert_different_hash(&v1, &v3);
+    assert_different_hash(&v2, &v3);
 }
 
 #[test]
@@ -248,11 +252,7 @@ fn test_lints_tracking_hash_different_construction_order() {
         (String::from("d"), Level::Forbid),
     ];
 
-    assert_eq!(v1.dep_tracking_hash(), v2.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
+    assert_same_hash(&v1, &v2);
 }
 
 #[test]
@@ -292,15 +292,9 @@ fn test_search_paths_tracking_hash_different_order() {
     v4.search_paths.push(SearchPath::from_cli_opt("dependency=ghi", JSON));
     v4.search_paths.push(SearchPath::from_cli_opt("framework=jkl", JSON));
 
-    assert!(v1.dep_tracking_hash() == v2.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() == v3.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() == v4.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
-    assert_eq!(v3.dep_tracking_hash(), v3.clone().dep_tracking_hash());
-    assert_eq!(v4.dep_tracking_hash(), v4.clone().dep_tracking_hash());
+    assert_same_hash(&v1, &v2);
+    assert_same_hash(&v1, &v3);
+    assert_same_hash(&v1, &v4);
 }
 
 #[test]
@@ -338,15 +332,9 @@ fn test_native_libs_tracking_hash_different_values() {
         (String::from("c"), None, NativeLibKind::Unspecified),
     ];
 
-    assert!(v1.dep_tracking_hash() != v2.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() != v3.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() != v4.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
-    assert_eq!(v3.dep_tracking_hash(), v3.clone().dep_tracking_hash());
-    assert_eq!(v4.dep_tracking_hash(), v4.clone().dep_tracking_hash());
+    assert_different_hash(&v1, &v2);
+    assert_different_hash(&v1, &v3);
+    assert_different_hash(&v1, &v4);
 }
 
 #[test]
@@ -374,14 +362,9 @@ fn test_native_libs_tracking_hash_different_order() {
         (String::from("b"), None, NativeLibKind::Framework),
     ];
 
-    assert!(v1.dep_tracking_hash() == v2.dep_tracking_hash());
-    assert!(v1.dep_tracking_hash() == v3.dep_tracking_hash());
-    assert!(v2.dep_tracking_hash() == v3.dep_tracking_hash());
-
-    // Check clone
-    assert_eq!(v1.dep_tracking_hash(), v1.clone().dep_tracking_hash());
-    assert_eq!(v2.dep_tracking_hash(), v2.clone().dep_tracking_hash());
-    assert_eq!(v3.dep_tracking_hash(), v3.clone().dep_tracking_hash());
+    assert_same_hash(&v1, &v2);
+    assert_same_hash(&v1, &v3);
+    assert_same_hash(&v2, &v3);
 }
 
 #[test]
@@ -391,8 +374,9 @@ fn test_codegen_options_tracking_hash() {
 
     macro_rules! untracked {
         ($name: ident, $non_default_value: expr) => {
+            assert_ne!(opts.cg.$name, $non_default_value);
             opts.cg.$name = $non_default_value;
-            assert_eq!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
+            assert_same_hash(&reference, &opts);
         };
     }
 
@@ -416,8 +400,9 @@ fn test_codegen_options_tracking_hash() {
     macro_rules! tracked {
         ($name: ident, $non_default_value: expr) => {
             opts = reference.clone();
+            assert_ne!(opts.cg.$name, $non_default_value);
             opts.cg.$name = $non_default_value;
-            assert_ne!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
+            assert_different_hash(&reference, &opts);
         };
     }
 
@@ -455,14 +440,41 @@ fn test_codegen_options_tracking_hash() {
 }
 
 #[test]
+fn test_top_level_options_tracked_no_crate() {
+    let reference = Options::default();
+    let mut opts;
+
+    macro_rules! tracked {
+        ($name: ident, $non_default_value: expr) => {
+            opts = reference.clone();
+            assert_ne!(opts.$name, $non_default_value);
+            opts.$name = $non_default_value;
+            // The crate hash should be the same
+            assert_eq!(reference.dep_tracking_hash(true), opts.dep_tracking_hash(true));
+            // The incremental hash should be different
+            assert_ne!(reference.dep_tracking_hash(false), opts.dep_tracking_hash(false));
+        };
+    }
+
+    // Make sure that changing a [TRACKED_NO_CRATE_HASH] option leaves the crate hash unchanged but changes the incremental hash.
+    // This list is in alphabetical order.
+    tracked!(remap_path_prefix, vec![("/home/bors/rust".into(), "src".into())]);
+    tracked!(
+        real_rust_source_base_dir,
+        Some("/home/bors/rust/.rustup/toolchains/nightly/lib/rustlib/src/rust".into())
+    );
+}
+
+#[test]
 fn test_debugging_options_tracking_hash() {
     let reference = Options::default();
     let mut opts = Options::default();
 
     macro_rules! untracked {
         ($name: ident, $non_default_value: expr) => {
+            assert_ne!(opts.debugging_opts.$name, $non_default_value);
             opts.debugging_opts.$name = $non_default_value;
-            assert_eq!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
+            assert_same_hash(&reference, &opts);
         };
     }
 
@@ -471,7 +483,7 @@ fn test_debugging_options_tracking_hash() {
     untracked!(ast_json, true);
     untracked!(ast_json_noexpand, true);
     untracked!(borrowck, String::from("other"));
-    untracked!(deduplicate_diagnostics, true);
+    untracked!(deduplicate_diagnostics, false);
     untracked!(dep_tasks, true);
     untracked!(dont_buffer_diagnostics, true);
     untracked!(dump_dep_graph, true);
@@ -515,7 +527,7 @@ fn test_debugging_options_tracking_hash() {
     untracked!(self_profile_events, Some(vec![String::new()]));
     untracked!(span_debug, true);
     untracked!(span_free_formats, true);
-    untracked!(strip, Strip::None);
+    untracked!(strip, Strip::Debuginfo);
     untracked!(terminal_width, Some(80));
     untracked!(threads, 99);
     untracked!(time, true);
@@ -532,8 +544,9 @@ fn test_debugging_options_tracking_hash() {
     macro_rules! tracked {
         ($name: ident, $non_default_value: expr) => {
             opts = reference.clone();
+            assert_ne!(opts.debugging_opts.$name, $non_default_value);
             opts.debugging_opts.$name = $non_default_value;
-            assert_ne!(reference.dep_tracking_hash(), opts.dep_tracking_hash());
+            assert_different_hash(&reference, &opts);
         };
     }
 
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 19ae5ce69c1..2ade1bb4f95 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1617,7 +1617,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             .map(Path::new)
             .filter(|_| {
                 // Only spend time on further checks if we have what to translate *to*.
-                sess.real_rust_source_base_dir.is_some()
+                sess.opts.real_rust_source_base_dir.is_some()
             })
             .filter(|virtual_dir| {
                 // Don't translate away `/rustc/$hash` if we're still remapping to it,
@@ -1629,11 +1629,11 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             debug!(
                 "try_to_translate_virtual_to_real(name={:?}): \
                  virtual_rust_source_base_dir={:?}, real_rust_source_base_dir={:?}",
-                name, virtual_rust_source_base_dir, sess.real_rust_source_base_dir,
+                name, virtual_rust_source_base_dir, sess.opts.real_rust_source_base_dir,
             );
 
             if let Some(virtual_dir) = virtual_rust_source_base_dir {
-                if let Some(real_dir) = &sess.real_rust_source_base_dir {
+                if let Some(real_dir) = &sess.opts.real_rust_source_base_dir {
                     if let rustc_span::FileName::Real(old_name) = name {
                         if let rustc_span::RealFileName::Named(one_path) = old_name {
                             if let Ok(rest) = one_path.strip_prefix(virtual_dir) {
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index d155276051e..4cd126988f9 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -943,7 +943,7 @@ pub(super) fn index_hir<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> &'tcx Indexe
         intravisit::walk_crate(&mut collector, tcx.untracked_crate);
 
         let crate_disambiguator = tcx.sess.local_crate_disambiguator();
-        let cmdline_args = tcx.sess.opts.dep_tracking_hash();
+        let cmdline_args = tcx.sess.opts.dep_tracking_hash(true);
         collector.finalize_and_compute_crate_hash(crate_disambiguator, &*tcx.cstore, cmdline_args)
     };
 
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 52a6e4ff924..1f5cb5b8abc 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -156,7 +156,7 @@ pub enum InstrumentCoverage {
     Off,
 }
 
-#[derive(Clone, PartialEq, Hash)]
+#[derive(Clone, PartialEq, Hash, Debug)]
 pub enum LinkerPluginLto {
     LinkerPlugin(PathBuf),
     LinkerPluginAuto,
@@ -172,7 +172,7 @@ impl LinkerPluginLto {
     }
 }
 
-#[derive(Clone, PartialEq, Hash)]
+#[derive(Clone, PartialEq, Hash, Debug)]
 pub enum SwitchWithOptPath {
     Enabled(Option<PathBuf>),
     Disabled,
@@ -702,6 +702,7 @@ impl Default for Options {
             cli_forced_codegen_units: None,
             cli_forced_thinlto_off: false,
             remap_path_prefix: Vec::new(),
+            real_rust_source_base_dir: None,
             edition: DEFAULT_EDITION,
             json_artifact_notifications: false,
             json_unused_externs: false,
@@ -778,7 +779,7 @@ pub enum CrateType {
 
 impl_stable_hash_via_hash!(CrateType);
 
-#[derive(Clone, Hash)]
+#[derive(Clone, Hash, Debug, PartialEq, Eq)]
 pub enum Passes {
     Some(Vec<String>),
     All,
@@ -1980,6 +1981,34 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         }
     }
 
+    // Try to find a directory containing the Rust `src`, for more details see
+    // the doc comment on the `real_rust_source_base_dir` field.
+    let tmp_buf;
+    let sysroot = match &sysroot_opt {
+        Some(s) => s,
+        None => {
+            tmp_buf = crate::filesearch::get_or_default_sysroot();
+            &tmp_buf
+        }
+    };
+    let real_rust_source_base_dir = {
+        // This is the location used by the `rust-src` `rustup` component.
+        let mut candidate = sysroot.join("lib/rustlib/src/rust");
+        if let Ok(metadata) = candidate.symlink_metadata() {
+            // Replace the symlink rustbuild creates, with its destination.
+            // We could try to use `fs::canonicalize` instead, but that might
+            // produce unnecessarily verbose path.
+            if metadata.file_type().is_symlink() {
+                if let Ok(symlink_dest) = std::fs::read_link(&candidate) {
+                    candidate = symlink_dest;
+                }
+            }
+        }
+
+        // Only use this directory if it has a file we can expect to always find.
+        if candidate.join("library/std/src/lib.rs").is_file() { Some(candidate) } else { None }
+    };
+
     Options {
         crate_types,
         optimize: opt_level,
@@ -2010,6 +2039,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         cli_forced_codegen_units: codegen_units,
         cli_forced_thinlto_off: disable_thinlto,
         remap_path_prefix,
+        real_rust_source_base_dir,
         edition,
         json_artifact_notifications,
         json_unused_externs,
@@ -2374,6 +2404,7 @@ crate mod dep_tracking {
 
     impl_dep_tracking_hash_for_sortable_vec_of!(String);
     impl_dep_tracking_hash_for_sortable_vec_of!(PathBuf);
+    impl_dep_tracking_hash_for_sortable_vec_of!((PathBuf, PathBuf));
     impl_dep_tracking_hash_for_sortable_vec_of!(CrateType);
     impl_dep_tracking_hash_for_sortable_vec_of!((String, lint::Level));
     impl_dep_tracking_hash_for_sortable_vec_of!((String, Option<String>, NativeLibKind));
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index fd26f50da5a..1c2a7f7716d 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -20,73 +20,112 @@ use std::num::NonZeroUsize;
 use std::path::PathBuf;
 use std::str;
 
-macro_rules! hash_option {
-    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, [UNTRACKED]) => {{}};
-    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, [TRACKED]) => {{
+macro_rules! insert {
+    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr) => {
         if $sub_hashes
             .insert(stringify!($opt_name), $opt_expr as &dyn dep_tracking::DepTrackingHash)
             .is_some()
         {
             panic!("duplicate key in CLI DepTrackingHash: {}", stringify!($opt_name))
         }
+    };
+}
+
+macro_rules! hash_opt {
+    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, $_for_crate_hash: ident, [UNTRACKED]) => {{}};
+    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, $_for_crate_hash: ident, [TRACKED]) => {{ insert!($opt_name, $opt_expr, $sub_hashes) }};
+    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, $for_crate_hash: ident, [TRACKED_NO_CRATE_HASH]) => {{
+        if !$for_crate_hash {
+            insert!($opt_name, $opt_expr, $sub_hashes)
+        }
     }};
+    ($opt_name:ident, $opt_expr:expr, $sub_hashes:expr, $_for_crate_hash: ident, [SUBSTRUCT]) => {{}};
+}
+
+macro_rules! hash_substruct {
+    ($opt_name:ident, $opt_expr:expr, $error_format:expr, $for_crate_hash:expr, $hasher:expr, [UNTRACKED]) => {{}};
+    ($opt_name:ident, $opt_expr:expr, $error_format:expr, $for_crate_hash:expr, $hasher:expr, [TRACKED]) => {{}};
+    ($opt_name:ident, $opt_expr:expr, $error_format:expr, $for_crate_hash:expr, $hasher:expr, [TRACKED_NO_CRATE_HASH]) => {{}};
+    ($opt_name:ident, $opt_expr:expr, $error_format:expr, $for_crate_hash:expr, $hasher:expr, [SUBSTRUCT]) => {
+        use crate::config::dep_tracking::DepTrackingHash;
+        $opt_expr.dep_tracking_hash($for_crate_hash, $error_format).hash($hasher, $error_format);
+    };
 }
 
 macro_rules! top_level_options {
-    (pub struct Options { $(
-        $opt:ident : $t:ty [$dep_tracking_marker:ident $($warn_val:expr, $warn_text:expr)*],
+    ( $( #[$top_level_attr:meta] )* pub struct Options { $(
+        $( #[$attr:meta] )*
+        $opt:ident : $t:ty [$dep_tracking_marker:ident],
     )* } ) => (
         #[derive(Clone)]
+        $( #[$top_level_attr] )*
         pub struct Options {
-            $(pub $opt: $t),*
+            $(
+                $( #[$attr] )*
+                pub $opt: $t
+            ),*
         }
 
         impl Options {
-            pub fn dep_tracking_hash(&self) -> u64 {
+            pub fn dep_tracking_hash(&self, for_crate_hash: bool) -> u64 {
                 let mut sub_hashes = BTreeMap::new();
                 $({
-                    hash_option!($opt,
-                                 &self.$opt,
-                                 &mut sub_hashes,
-                                 [$dep_tracking_marker $($warn_val,
-                                                         $warn_text,
-                                                         self.error_format)*]);
+                    hash_opt!($opt,
+                                &self.$opt,
+                                &mut sub_hashes,
+                                for_crate_hash,
+                                [$dep_tracking_marker]);
                 })*
                 let mut hasher = DefaultHasher::new();
                 dep_tracking::stable_hash(sub_hashes,
                                           &mut hasher,
                                           self.error_format);
+                $({
+                    hash_substruct!($opt,
+                        &self.$opt,
+                        self.error_format,
+                        for_crate_hash,
+                        &mut hasher,
+                        [$dep_tracking_marker]);
+                })*
                 hasher.finish()
             }
         }
     );
 }
 
-// The top-level command-line options struct.
-//
-// For each option, one has to specify how it behaves with regard to the
-// dependency tracking system of incremental compilation. This is done via the
-// square-bracketed directive after the field type. The options are:
-//
-// [TRACKED]
-// A change in the given field will cause the compiler to completely clear the
-// incremental compilation cache before proceeding.
-//
-// [UNTRACKED]
-// Incremental compilation is not influenced by this option.
-//
-// If you add a new option to this struct or one of the sub-structs like
-// `CodegenOptions`, think about how it influences incremental compilation. If in
-// doubt, specify [TRACKED], which is always "correct" but might lead to
-// unnecessary re-compilation.
 top_level_options!(
+    /// The top-level command-line options struct.
+    ///
+    /// For each option, one has to specify how it behaves with regard to the
+    /// dependency tracking system of incremental compilation. This is done via the
+    /// square-bracketed directive after the field type. The options are:
+    ///
+    /// - `[TRACKED]`
+    /// A change in the given field will cause the compiler to completely clear the
+    /// incremental compilation cache before proceeding.
+    ///
+    /// - `[TRACKED_NO_CRATE_HASH]`
+    /// Same as `[TRACKED]`, but will not affect the crate hash. This is useful for options that only
+    /// affect the incremental cache.
+    ///
+    /// - `[UNTRACKED]`
+    /// Incremental compilation is not influenced by this option.
+    ///
+    /// - `[SUBSTRUCT]`
+    /// Second-level sub-structs containing more options.
+    ///
+    /// If you add a new option to this struct or one of the sub-structs like
+    /// `CodegenOptions`, think about how it influences incremental compilation. If in
+    /// doubt, specify `[TRACKED]`, which is always "correct" but might lead to
+    /// unnecessary re-compilation.
     pub struct Options {
-        // The crate config requested for the session, which may be combined
-        // with additional crate configurations during the compile process.
+        /// The crate config requested for the session, which may be combined
+        /// with additional crate configurations during the compile process.
         crate_types: Vec<CrateType> [TRACKED],
         optimize: OptLevel [TRACKED],
-        // Include the `debug_assertions` flag in dependency tracking, since it
-        // can influence whether overflow checks are done or not.
+        /// Include the `debug_assertions` flag in dependency tracking, since it
+        /// can influence whether overflow checks are done or not.
         debug_assertions: bool [TRACKED],
         debuginfo: DebugInfo [TRACKED],
         lint_opts: Vec<(String, lint::Level)> [TRACKED],
@@ -102,52 +141,60 @@ top_level_options!(
         test: bool [TRACKED],
         error_format: ErrorOutputType [UNTRACKED],
 
-        // If `Some`, enable incremental compilation, using the given
-        // directory to store intermediate results.
+        /// If `Some`, enable incremental compilation, using the given
+        /// directory to store intermediate results.
         incremental: Option<PathBuf> [UNTRACKED],
 
-        debugging_opts: DebuggingOptions [TRACKED],
+        debugging_opts: DebuggingOptions [SUBSTRUCT],
         prints: Vec<PrintRequest> [UNTRACKED],
-        // Determines which borrow checker(s) to run. This is the parsed, sanitized
-        // version of `debugging_opts.borrowck`, which is just a plain string.
+        /// Determines which borrow checker(s) to run. This is the parsed, sanitized
+        /// version of `debugging_opts.borrowck`, which is just a plain string.
         borrowck_mode: BorrowckMode [UNTRACKED],
-        cg: CodegenOptions [TRACKED],
+        cg: CodegenOptions [SUBSTRUCT],
         externs: Externs [UNTRACKED],
         extern_dep_specs: ExternDepSpecs [UNTRACKED],
         crate_name: Option<String> [TRACKED],
-        // An optional name to use as the crate for std during std injection,
-        // written `extern crate name as std`. Defaults to `std`. Used by
-        // out-of-tree drivers.
+        /// An optional name to use as the crate for std during std injection,
+        /// written `extern crate name as std`. Defaults to `std`. Used by
+        /// out-of-tree drivers.
         alt_std_name: Option<String> [TRACKED],
-        // Indicates how the compiler should treat unstable features.
+        /// Indicates how the compiler should treat unstable features.
         unstable_features: UnstableFeatures [TRACKED],
 
-        // Indicates whether this run of the compiler is actually rustdoc. This
-        // is currently just a hack and will be removed eventually, so please
-        // try to not rely on this too much.
+        /// Indicates whether this run of the compiler is actually rustdoc. This
+        /// is currently just a hack and will be removed eventually, so please
+        /// try to not rely on this too much.
         actually_rustdoc: bool [TRACKED],
 
-        // Control path trimming.
+        /// Control path trimming.
         trimmed_def_paths: TrimmedDefPaths [TRACKED],
 
-        // Specifications of codegen units / ThinLTO which are forced as a
-        // result of parsing command line options. These are not necessarily
-        // what rustc was invoked with, but massaged a bit to agree with
-        // commands like `--emit llvm-ir` which they're often incompatible with
-        // if we otherwise use the defaults of rustc.
+        /// Specifications of codegen units / ThinLTO which are forced as a
+        /// result of parsing command line options. These are not necessarily
+        /// what rustc was invoked with, but massaged a bit to agree with
+        /// commands like `--emit llvm-ir` which they're often incompatible with
+        /// if we otherwise use the defaults of rustc.
         cli_forced_codegen_units: Option<usize> [UNTRACKED],
         cli_forced_thinlto_off: bool [UNTRACKED],
 
-        // Remap source path prefixes in all output (messages, object files, debug, etc.).
-        remap_path_prefix: Vec<(PathBuf, PathBuf)> [UNTRACKED],
+        /// Remap source path prefixes in all output (messages, object files, debug, etc.).
+        remap_path_prefix: Vec<(PathBuf, PathBuf)> [TRACKED_NO_CRATE_HASH],
+        /// Base directory containing the `src/` for the Rust standard library, and
+        /// potentially `rustc` as well, if we can can find it. Right now it's always
+        /// `$sysroot/lib/rustlib/src/rust` (i.e. the `rustup` `rust-src` component).
+        ///
+        /// This directory is what the virtual `/rustc/$hash` is translated back to,
+        /// if Rust was built with path remapping to `/rustc/$hash` enabled
+        /// (the `rust.remap-debuginfo` option in `config.toml`).
+        real_rust_source_base_dir: Option<PathBuf> [TRACKED_NO_CRATE_HASH],
 
         edition: Edition [TRACKED],
 
-        // `true` if we're emitting JSON blobs about each artifact produced
-        // by the compiler.
+        /// `true` if we're emitting JSON blobs about each artifact produced
+        /// by the compiler.
         json_artifact_notifications: bool [TRACKED],
 
-        // `true` if we're emitting a JSON blob containing the unused externs
+        /// `true` if we're emitting a JSON blob containing the unused externs
         json_unused_externs: bool [UNTRACKED],
 
         pretty: Option<PpMode> [UNTRACKED],
@@ -166,10 +213,10 @@ macro_rules! options {
     ($struct_name:ident, $setter_name:ident, $defaultfn:ident,
      $buildfn:ident, $prefix:expr, $outputname:expr,
      $stat:ident, $mod_desc:ident, $mod_set:ident,
-     $($opt:ident : $t:ty = (
+     $($( #[$attr:meta] )* $opt:ident : $t:ty = (
         $init:expr,
         $parse:ident,
-        [$dep_tracking_marker:ident $(($dep_warn_val:expr, $dep_warn_text:expr))*],
+        [$dep_tracking_marker:ident],
         $desc:expr)
      ),* ,) =>
 (
@@ -177,7 +224,7 @@ macro_rules! options {
     pub struct $struct_name { $(pub $opt: $t),* }
 
     pub fn $defaultfn() -> $struct_name {
-        $struct_name { $($opt: $init),* }
+        $struct_name { $( $( #[$attr] )* $opt: $init),* }
     }
 
     pub fn $buildfn(matches: &getopts::Matches, error_format: ErrorOutputType) -> $struct_name
@@ -219,18 +266,21 @@ macro_rules! options {
         return op;
     }
 
-    impl dep_tracking::DepTrackingHash for $struct_name {
-        fn hash(&self, hasher: &mut DefaultHasher, error_format: ErrorOutputType) {
+    impl $struct_name {
+        fn dep_tracking_hash(&self, _for_crate_hash: bool, error_format: ErrorOutputType) -> u64 {
             let mut sub_hashes = BTreeMap::new();
             $({
-                hash_option!($opt,
-                             &self.$opt,
-                             &mut sub_hashes,
-                             [$dep_tracking_marker $($dep_warn_val,
-                                                     $dep_warn_text,
-                                                     error_format)*]);
+                hash_opt!($opt,
+                            &self.$opt,
+                            &mut sub_hashes,
+                            _for_crate_hash,
+                            [$dep_tracking_marker]);
             })*
-            dep_tracking::stable_hash(sub_hashes, hasher, error_format);
+            let mut hasher = DefaultHasher::new();
+            dep_tracking::stable_hash(sub_hashes,
+                                        &mut hasher,
+                                        error_format);
+            hasher.finish()
         }
     }
 
@@ -1128,7 +1178,7 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
     self_profile: SwitchWithOptPath = (SwitchWithOptPath::Disabled,
         parse_switch_with_opt_path, [UNTRACKED],
         "run the self profiler and output the raw event data"),
-    // keep this in sync with the event filter names in librustc_data_structures/profiling.rs
+    /// keep this in sync with the event filter names in librustc_data_structures/profiling.rs
     self_profile_events: Option<Vec<String>> = (None, parse_opt_comma_list, [UNTRACKED],
         "specify the events recorded by the self profiler;
         for example: `-Z self-profile-events=default,query-keys`
@@ -1140,7 +1190,7 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "show spans for compiler debugging (expr|pat|ty)"),
     span_debug: bool = (false, parse_bool, [UNTRACKED],
         "forward proc_macro::Span's `Debug` impl to `Span`"),
-    // o/w tests have closure@path
+    /// o/w tests have closure@path
     span_free_formats: bool = (false, parse_bool, [UNTRACKED],
         "exclude spans when debug-printing compiler state (default: no)"),
     src_hash_algorithm: Option<SourceFileHashAlgorithm> = (None, parse_src_file_hash, [TRACKED],
@@ -1161,10 +1211,10 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "select processor to schedule for (`rustc --print target-cpus` for details)"),
     thinlto: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "enable ThinLTO when possible"),
-    // We default to 1 here since we want to behave like
-    // a sequential compiler for now. This'll likely be adjusted
-    // in the future. Note that -Zthreads=0 is the way to get
-    // the num_cpus behavior.
+    /// We default to 1 here since we want to behave like
+    /// a sequential compiler for now. This'll likely be adjusted
+    /// in the future. Note that -Zthreads=0 is the way to get
+    /// the num_cpus behavior.
     threads: usize = (1, parse_threads, [UNTRACKED],
         "use a thread pool with N threads"),
     time: bool = (false, parse_bool, [UNTRACKED],
@@ -1220,7 +1270,7 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
     // - compiler/rustc_interface/src/tests.rs
 }
 
-#[derive(Clone, Hash)]
+#[derive(Clone, Hash, PartialEq, Eq, Debug)]
 pub enum WasiExecModel {
     Command,
     Reactor,
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 7bff634fb2d..e7dfc4b8c41 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -214,15 +214,6 @@ pub struct Session {
     /// drown everything else in noise.
     miri_unleashed_features: Lock<Vec<(Span, Option<Symbol>)>>,
 
-    /// Base directory containing the `src/` for the Rust standard library, and
-    /// potentially `rustc` as well, if we can can find it. Right now it's always
-    /// `$sysroot/lib/rustlib/src/rust` (i.e. the `rustup` `rust-src` component).
-    ///
-    /// This directory is what the virtual `/rustc/$hash` is translated back to,
-    /// if Rust was built with path remapping to `/rustc/$hash` enabled
-    /// (the `rust.remap-debuginfo` option in `config.toml`).
-    pub real_rust_source_base_dir: Option<PathBuf>,
-
     /// Architecture to use for interpreting asm!.
     pub asm_arch: Option<InlineAsmArch>,
 
@@ -1390,26 +1381,6 @@ pub fn build_session(
         _ => CtfeBacktrace::Disabled,
     });
 
-    // Try to find a directory containing the Rust `src`, for more details see
-    // the doc comment on the `real_rust_source_base_dir` field.
-    let real_rust_source_base_dir = {
-        // This is the location used by the `rust-src` `rustup` component.
-        let mut candidate = sysroot.join("lib/rustlib/src/rust");
-        if let Ok(metadata) = candidate.symlink_metadata() {
-            // Replace the symlink rustbuild creates, with its destination.
-            // We could try to use `fs::canonicalize` instead, but that might
-            // produce unnecessarily verbose path.
-            if metadata.file_type().is_symlink() {
-                if let Ok(symlink_dest) = std::fs::read_link(&candidate) {
-                    candidate = symlink_dest;
-                }
-            }
-        }
-
-        // Only use this directory if it has a file we can expect to always find.
-        if candidate.join("library/std/src/lib.rs").is_file() { Some(candidate) } else { None }
-    };
-
     let asm_arch =
         if target_cfg.allow_asm { InlineAsmArch::from_str(&target_cfg.arch).ok() } else { None };
 
@@ -1453,7 +1424,6 @@ pub fn build_session(
         system_library_path: OneThread::new(RefCell::new(Default::default())),
         ctfe_backtrace,
         miri_unleashed_features: Lock::new(Default::default()),
-        real_rust_source_base_dir,
         asm_arch,
         target_features: FxHashSet::default(),
         known_attrs: Lock::new(MarkedAttrs::new()),
diff --git a/src/test/incremental/commandline-args.rs b/src/test/incremental/commandline-args.rs
index 08a0232f661..35b7183db7f 100644
--- a/src/test/incremental/commandline-args.rs
+++ b/src/test/incremental/commandline-args.rs
@@ -2,20 +2,23 @@
 // the cache while changing an untracked one doesn't.
 
 // ignore-asmjs wasm2js does not support source maps yet
-// revisions:rpass1 rpass2 rpass3
+// revisions:rpass1 rpass2 rpass3 rpass4
 // compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 
 #![rustc_partition_codegened(module="commandline_args", cfg="rpass2")]
 #![rustc_partition_reused(module="commandline_args", cfg="rpass3")]
+#![rustc_partition_codegened(module="commandline_args", cfg="rpass4")]
 
 // Between revisions 1 and 2, we are changing the debuginfo-level, which should
 // invalidate the cache. Between revisions 2 and 3, we are adding `--verbose`
-// which should have no effect on the cache:
+// which should have no effect on the cache. Between revisions, we are adding
+// `--remap-path-prefix` which should invalidate the cache:
 //[rpass1] compile-flags: -C debuginfo=0
 //[rpass2] compile-flags: -C debuginfo=2
 //[rpass3] compile-flags: -C debuginfo=2 --verbose
+//[rpass4] compile-flags: -C debuginfo=2 --verbose --remap-path-prefix=/home/bors/rust=src
 
 pub fn main() {
     // empty
diff --git a/src/test/run-make-fulldeps/incr-add-rust-src-component/Makefile b/src/test/run-make-fulldeps/incr-add-rust-src-component/Makefile
index 50ff3dd56ce..371f94715a8 100644
--- a/src/test/run-make-fulldeps/incr-add-rust-src-component/Makefile
+++ b/src/test/run-make-fulldeps/incr-add-rust-src-component/Makefile
@@ -1,7 +1,7 @@
 -include ../tools.mk
 
 # rust-lang/rust#70924: Test that if we add rust-src component in between two
-# incremetnal compiles, the compiler does not ICE on the second.
+# incremental compiles, the compiler does not ICE on the second.
 
 # This test uses `ln -s` rather than copying to save testing time, but its
 # usage doesn't work on windows. So ignore windows.