Auto merge of #142903 - cjgillot:local-def-path-hash, r=compiler-errors

Only inherit local hash for paths

`DefPathHash`, as the counterpart of `DefId` that is stable across compiler invocations, is comprised of 2 parts. The first one is the `StableCrateId`, stable form of `CrateNum`. The second is 64 complementary bits to identify the crate-local definition.

The current implementation always hashes the full 128 bits when (1) trying to create a new child `DefPathHash` or (2) hashing a `CrateNum` or a `LocalDefId`. But we only need half that information: `LocalDefId` means that the `StableCrateId` is always the current crate's ; `CrateNum` means that we do not care about the local part.

As stable hashing is very hot in the query system, in particular hashing definitions, this is a big deal.

We still want the local part to change when the `StableCrateId` changes, to make incr-compilation errors less painful, ie. increase the likelihood that if will magically disappear by changing some code.

This PR sprinkles some `#[inline]` attributes on small functions that appeared in profiles.

7 files changed, 39 insertions, 16 deletions

diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index 8aec11a2e81..698406d53a4 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -140,7 +140,9 @@ impl DefKey {
     pub(crate) fn compute_stable_hash(&self, parent: DefPathHash) -> DefPathHash {
         let mut hasher = StableHasher::new();
 
-        parent.hash(&mut hasher);
+        // The new path is in the same crate as `parent`, and will contain the stable_crate_id.
+        // Therefore, we only need to include information of the parent's local hash.
+        parent.local_hash().hash(&mut hasher);
 
         let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;
 
@@ -355,8 +357,16 @@ impl Definitions {
             },
         };
 
-        let parent_hash = DefPathHash::new(stable_crate_id, Hash64::ZERO);
-        let def_path_hash = key.compute_stable_hash(parent_hash);
+        // We want *both* halves of a DefPathHash to depend on the crate-id of the defining crate.
+        // The crate-id can be more easily changed than the DefPath of an item, so, in the case of
+        // a crate-local DefPathHash collision, the user can simply "roll the dice again" for all
+        // DefPathHashes in the crate by changing the crate disambiguator (e.g. via bumping the
+        // crate's version number).
+        //
+        // Children paths will only hash the local portion, and still inherit the change to the
+        // root hash.
+        let def_path_hash =
+            DefPathHash::new(stable_crate_id, Hash64::new(stable_crate_id.as_u64()));
 
         // Create the root definition.
         let mut table = DefPathTable::new(stable_crate_id);
diff --git a/compiler/rustc_hir/src/tests.rs b/compiler/rustc_hir/src/tests.rs
index 18c2bfdac8c..3b797c1f103 100644
--- a/compiler/rustc_hir/src/tests.rs
+++ b/compiler/rustc_hir/src/tests.rs
@@ -28,7 +28,8 @@ fn def_path_hash_depends_on_crate_id() {
         assert_ne!(h0.local_hash(), h1.local_hash());
 
         fn mk_test_hash(stable_crate_id: StableCrateId) -> DefPathHash {
-            let parent_hash = DefPathHash::new(stable_crate_id, Hash64::ZERO);
+            let parent_hash =
+                DefPathHash::new(stable_crate_id, Hash64::new(stable_crate_id.as_u64()));
 
             let key = DefKey {
                 parent: None,
diff --git a/compiler/rustc_span/src/def_id.rs b/compiler/rustc_span/src/def_id.rs
index 641bac88ad0..77f01548bca 100644
--- a/compiler/rustc_span/src/def_id.rs
+++ b/compiler/rustc_span/src/def_id.rs
@@ -110,6 +110,7 @@ impl DefPathHash {
 
     /// Builds a new [DefPathHash] with the given [StableCrateId] and
     /// `local_hash`, where `local_hash` must be unique within its crate.
+    #[inline]
     pub fn new(stable_crate_id: StableCrateId, local_hash: Hash64) -> DefPathHash {
         DefPathHash(Fingerprint::new(stable_crate_id.0, local_hash))
     }
@@ -404,21 +405,21 @@ rustc_data_structures::define_id_collections!(
 impl<CTX: HashStableContext> HashStable<CTX> for DefId {
     #[inline]
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        self.to_stable_hash_key(hcx).hash_stable(hcx, hasher);
+        hcx.def_path_hash(*self).hash_stable(hcx, hasher);
     }
 }
 
 impl<CTX: HashStableContext> HashStable<CTX> for LocalDefId {
     #[inline]
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        self.to_stable_hash_key(hcx).hash_stable(hcx, hasher);
+        hcx.def_path_hash(self.to_def_id()).local_hash().hash_stable(hcx, hasher);
     }
 }
 
 impl<CTX: HashStableContext> HashStable<CTX> for CrateNum {
     #[inline]
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        self.to_stable_hash_key(hcx).hash_stable(hcx, hasher);
+        self.as_def_id().to_stable_hash_key(hcx).stable_crate_id().hash_stable(hcx, hasher);
     }
 }
 
@@ -464,30 +465,36 @@ macro_rules! typed_def_id {
         pub struct $Name(DefId);
 
         impl $Name {
+            #[inline]
             pub const fn new_unchecked(def_id: DefId) -> Self {
                 Self(def_id)
             }
 
+            #[inline]
             pub fn to_def_id(self) -> DefId {
                 self.into()
             }
 
+            #[inline]
             pub fn is_local(self) -> bool {
                 self.0.is_local()
             }
 
+            #[inline]
             pub fn as_local(self) -> Option<$LocalName> {
                 self.0.as_local().map($LocalName::new_unchecked)
             }
         }
 
         impl From<$LocalName> for $Name {
+            #[inline]
             fn from(local: $LocalName) -> Self {
                 Self(local.0.to_def_id())
             }
         }
 
         impl From<$Name> for DefId {
+            #[inline]
             fn from(typed: $Name) -> Self {
                 typed.0
             }
@@ -500,26 +507,31 @@ macro_rules! typed_def_id {
         impl !PartialOrd for $LocalName {}
 
         impl $LocalName {
+            #[inline]
             pub const fn new_unchecked(def_id: LocalDefId) -> Self {
                 Self(def_id)
             }
 
+            #[inline]
             pub fn to_def_id(self) -> DefId {
                 self.0.into()
             }
 
+            #[inline]
             pub fn to_local_def_id(self) -> LocalDefId {
                 self.0
             }
         }
 
         impl From<$LocalName> for LocalDefId {
+            #[inline]
             fn from(typed: $LocalName) -> Self {
                 typed.0
             }
         }
 
         impl From<$LocalName> for DefId {
+            #[inline]
             fn from(typed: $LocalName) -> Self {
                 typed.0.into()
             }
diff --git a/tests/mir-opt/inline/cycle.rs b/tests/mir-opt/inline/cycle.rs
index 383d0796a88..6e0f45bb3e9 100644
--- a/tests/mir-opt/inline/cycle.rs
+++ b/tests/mir-opt/inline/cycle.rs
@@ -13,7 +13,7 @@ fn f(g: impl Fn()) {
 #[inline(always)]
 fn g() {
     // CHECK-LABEL: fn g(
-    // CHECK-NOT: (inlined f::<fn() {main}>)
+    // CHECK-NOT: inlined
     f(main);
 }
 
diff --git a/tests/ui/symbol-names/basic.legacy.stderr b/tests/ui/symbol-names/basic.legacy.stderr
index 167262dcf06..a028f433172 100644
--- a/tests/ui/symbol-names/basic.legacy.stderr
+++ b/tests/ui/symbol-names/basic.legacy.stderr
@@ -1,10 +1,10 @@
-error: symbol-name(_ZN5basic4main17hc88b9d80a69d119aE)
+error: symbol-name(_ZN5basic4main17h1dddcfd03744167fE)
   --> $DIR/basic.rs:8:1
    |
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(basic::main::hc88b9d80a69d119a)
+error: demangling(basic::main::h1dddcfd03744167f)
   --> $DIR/basic.rs:8:1
    |
 LL | #[rustc_symbol_name]
diff --git a/tests/ui/symbol-names/issue-60925.legacy.stderr b/tests/ui/symbol-names/issue-60925.legacy.stderr
index 4e17bdc4577..14cbd877d9f 100644
--- a/tests/ui/symbol-names/issue-60925.legacy.stderr
+++ b/tests/ui/symbol-names/issue-60925.legacy.stderr
@@ -1,10 +1,10 @@
-error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17hbddb77d6f71afb32E)
+error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17h4b3099ec5dc5d306E)
   --> $DIR/issue-60925.rs:21:9
    |
 LL |         #[rustc_symbol_name]
    |         ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::hbddb77d6f71afb32)
+error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::h4b3099ec5dc5d306)
   --> $DIR/issue-60925.rs:21:9
    |
 LL |         #[rustc_symbol_name]
diff --git a/tests/ui/thir-print/thir-tree-match.stdout b/tests/ui/thir-print/thir-tree-match.stdout
index 910582ae4d9..2049c531abd 100644
--- a/tests/ui/thir-print/thir-tree-match.stdout
+++ b/tests/ui/thir-print/thir-tree-match.stdout
@@ -94,7 +94,7 @@ body:
                                                                                                 did: DefId(0:10 ~ thir_tree_match[fcf8]::Foo)
                                                                                                 variants: [VariantDef { def_id: DefId(0:11 ~ thir_tree_match[fcf8]::Foo::FooOne), ctor: Some((Fn, DefId(0:12 ~ thir_tree_match[fcf8]::Foo::FooOne::{constructor#0}))), name: "FooOne", discr: Relative(0), fields: [FieldDef { did: DefId(0:13 ~ thir_tree_match[fcf8]::Foo::FooOne::0), name: "0", vis: Restricted(DefId(0:0 ~ thir_tree_match[fcf8])), safety: Safe, value: None }], tainted: None, flags:  }, VariantDef { def_id: DefId(0:14 ~ thir_tree_match[fcf8]::Foo::FooTwo), ctor: Some((Const, DefId(0:15 ~ thir_tree_match[fcf8]::Foo::FooTwo::{constructor#0}))), name: "FooTwo", discr: Relative(1), fields: [], tainted: None, flags:  }]
                                                                                                 flags: IS_ENUM
-                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 3477539199540094892 }
+                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 13397682652773712997 }
                                                                                         args: []
                                                                                         variant_index: 0
                                                                                         subpatterns: [
@@ -108,7 +108,7 @@ body:
                                                                                                                 did: DefId(0:3 ~ thir_tree_match[fcf8]::Bar)
                                                                                                                 variants: [VariantDef { def_id: DefId(0:4 ~ thir_tree_match[fcf8]::Bar::First), ctor: Some((Const, DefId(0:5 ~ thir_tree_match[fcf8]::Bar::First::{constructor#0}))), name: "First", discr: Relative(0), fields: [], tainted: None, flags:  }, VariantDef { def_id: DefId(0:6 ~ thir_tree_match[fcf8]::Bar::Second), ctor: Some((Const, DefId(0:7 ~ thir_tree_match[fcf8]::Bar::Second::{constructor#0}))), name: "Second", discr: Relative(1), fields: [], tainted: None, flags:  }, VariantDef { def_id: DefId(0:8 ~ thir_tree_match[fcf8]::Bar::Third), ctor: Some((Const, DefId(0:9 ~ thir_tree_match[fcf8]::Bar::Third::{constructor#0}))), name: "Third", discr: Relative(2), fields: [], tainted: None, flags:  }]
                                                                                                                 flags: IS_ENUM
-                                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 10333377570083945360 }
+                                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 7908585036048874241 }
                                                                                                         args: []
                                                                                                         variant_index: 0
                                                                                                         subpatterns: []
@@ -156,7 +156,7 @@ body:
                                                                                                 did: DefId(0:10 ~ thir_tree_match[fcf8]::Foo)
                                                                                                 variants: [VariantDef { def_id: DefId(0:11 ~ thir_tree_match[fcf8]::Foo::FooOne), ctor: Some((Fn, DefId(0:12 ~ thir_tree_match[fcf8]::Foo::FooOne::{constructor#0}))), name: "FooOne", discr: Relative(0), fields: [FieldDef { did: DefId(0:13 ~ thir_tree_match[fcf8]::Foo::FooOne::0), name: "0", vis: Restricted(DefId(0:0 ~ thir_tree_match[fcf8])), safety: Safe, value: None }], tainted: None, flags:  }, VariantDef { def_id: DefId(0:14 ~ thir_tree_match[fcf8]::Foo::FooTwo), ctor: Some((Const, DefId(0:15 ~ thir_tree_match[fcf8]::Foo::FooTwo::{constructor#0}))), name: "FooTwo", discr: Relative(1), fields: [], tainted: None, flags:  }]
                                                                                                 flags: IS_ENUM
-                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 3477539199540094892 }
+                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 13397682652773712997 }
                                                                                         args: []
                                                                                         variant_index: 0
                                                                                         subpatterns: [
@@ -208,7 +208,7 @@ body:
                                                                                                 did: DefId(0:10 ~ thir_tree_match[fcf8]::Foo)
                                                                                                 variants: [VariantDef { def_id: DefId(0:11 ~ thir_tree_match[fcf8]::Foo::FooOne), ctor: Some((Fn, DefId(0:12 ~ thir_tree_match[fcf8]::Foo::FooOne::{constructor#0}))), name: "FooOne", discr: Relative(0), fields: [FieldDef { did: DefId(0:13 ~ thir_tree_match[fcf8]::Foo::FooOne::0), name: "0", vis: Restricted(DefId(0:0 ~ thir_tree_match[fcf8])), safety: Safe, value: None }], tainted: None, flags:  }, VariantDef { def_id: DefId(0:14 ~ thir_tree_match[fcf8]::Foo::FooTwo), ctor: Some((Const, DefId(0:15 ~ thir_tree_match[fcf8]::Foo::FooTwo::{constructor#0}))), name: "FooTwo", discr: Relative(1), fields: [], tainted: None, flags:  }]
                                                                                                 flags: IS_ENUM
-                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 3477539199540094892 }
+                                                                                                repr: ReprOptions { int: None, align: None, pack: None, flags: , field_shuffle_seed: 13397682652773712997 }
                                                                                         args: []
                                                                                         variant_index: 1
                                                                                         subpatterns: []