Shrink `SubregionOrigin`.

It's currently 120 bytes on x86-64, due to one oversized variant
(`Subtype`). This commit boxes `Subtype`'s contents, reducing the size
of `SubregionOrigin` to 32 bytes.

The change speeds things up by avoiding lots of `memcpy` calls, mostly
relating to `RegionConstraintData::constraints`, which is a `BTreeMap`
with `SubregionOrigin` values.

diff --git a/src/librustc/infer/equate.rs b/src/librustc/infer/equate.rs
index 5dfa0d29daf1b7e5647bfd791e7ebaba4881eca5..96d40bc81add2633eecb641999b0a4daf965baea 100644 (file)
--- a/src/librustc/infer/equate.rs
+++ b/src/librustc/infer/equate.rs
@@ -97,7 +97,7 @@ fn regions(&mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>)
                self.tag(),
                a,
                b);
-        let origin = Subtype(self.fields.trace.clone());
+        let origin = Subtype(box self.fields.trace.clone());
         self.fields.infcx.borrow_region_constraints()
                          .make_eqregion(origin, a, b);
         Ok(a)

diff --git a/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs b/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs
index b4fb018920647f916f7d4689bd02ecee211a875b..5f3c5fed3a3b25c5c778acfa296d0ad51f27dc80 100644 (file)
--- a/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -30,7 +30,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
             Some(RegionResolutionError::SubSupConflict(
                 vid,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -50,7 +50,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
             Some(RegionResolutionError::SubSupConflict(
                 vid,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -70,7 +70,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
             Some(RegionResolutionError::SubSupConflict(
                 vid,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -92,7 +92,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
                 _,
                 _,
                 _,
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -108,7 +108,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
             )),
 
             Some(RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -125,7 +125,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
             )),
 
             Some(RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),
@@ -142,7 +142,7 @@ pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder
             )),
 
             Some(RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(TypeTrace {
+                SubregionOrigin::Subtype(box TypeTrace {
                     cause,
                     values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
                 }),

diff --git a/src/librustc/infer/error_reporting/note.rs b/src/librustc/infer/error_reporting/note.rs
index caed4288892eff2844e9a0c4728647577ff9a75e..115ffea97bf1a47a3e3a0809f3a90163068d70e7 100644 (file)
--- a/src/librustc/infer/error_reporting/note.rs
+++ b/src/librustc/infer/error_reporting/note.rs
@@ -138,7 +138,7 @@ pub(super) fn report_concrete_failure(&self,
                                           sup: Region<'tcx>)
                                           -> DiagnosticBuilder<'tcx> {
         match origin {
-            infer::Subtype(trace) => {
+            infer::Subtype(box trace) => {
                 let terr = TypeError::RegionsDoesNotOutlive(sup, sub);
                 let mut err = self.report_and_explain_type_error(trace, &terr);
                 self.tcx.note_and_explain_region(region_scope_tree, &mut err, "", sup, "...");
@@ -450,7 +450,7 @@ pub(super) fn report_placeholder_failure(
     ) -> DiagnosticBuilder<'tcx> {
         // I can't think how to do better than this right now. -nikomatsakis
         match placeholder_origin {
-            infer::Subtype(trace) => {
+            infer::Subtype(box trace) => {
                 let terr = TypeError::RegionsPlaceholderMismatch;
                 self.report_and_explain_type_error(trace, &terr)
             }

diff --git a/src/librustc/infer/glb.rs b/src/librustc/infer/glb.rs
index 2cef521176269fb8f6c35e01e65f486819891674..10e45321a6d6ae5e2d3ecf4fbc3b40546f7e6f13 100644 (file)
--- a/src/librustc/infer/glb.rs
+++ b/src/librustc/infer/glb.rs
@@ -57,7 +57,7 @@ fn regions(&mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>)
                a,
                b);
 
-        let origin = Subtype(self.fields.trace.clone());
+        let origin = Subtype(box self.fields.trace.clone());
         Ok(self.fields.infcx.borrow_region_constraints().glb_regions(self.tcx(), origin, a, b))
     }
 

diff --git a/src/librustc/infer/lub.rs b/src/librustc/infer/lub.rs
index e20372f1513712359a007ba5af3a4c3e34c7c345..8b64cda7bd26d7e22e335c47f4fd3cfa4d5ed13d 100644 (file)
--- a/src/librustc/infer/lub.rs
+++ b/src/librustc/infer/lub.rs
@@ -57,7 +57,7 @@ fn regions(&mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>)
                a,
                b);
 
-        let origin = Subtype(self.fields.trace.clone());
+        let origin = Subtype(box self.fields.trace.clone());
         Ok(self.fields.infcx.borrow_region_constraints().lub_regions(self.tcx(), origin, a, b))
     }
 

diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index 8638f42976f046daee626580817142e3feafda6f..a886c44a4792d2513666a746e69cdf05ac251eb0 100644 (file)
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -254,7 +254,7 @@ pub struct TypeTrace<'tcx> {
 #[derive(Clone, Debug)]
 pub enum SubregionOrigin<'tcx> {
     /// Arose from a subtyping relation
-    Subtype(TypeTrace<'tcx>),
+    Subtype(Box<TypeTrace<'tcx>>),
 
     /// Stack-allocated closures cannot outlive innermost loop
     /// or function so as to ensure we only require finite stack
@@ -340,6 +340,10 @@ pub enum SubregionOrigin<'tcx> {
     },
 }
 
+// `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(SubregionOrigin<'_>, 32);
+
 /// Places that type/region parameters can appear.
 #[derive(Clone, Copy, Debug)]
 pub enum ParameterOrigin {

diff --git a/src/librustc/infer/sub.rs b/src/librustc/infer/sub.rs
index cd1d206b5fca1282af18ff333f56c894678dfff0..76db55ecfa8ef70a4dc8d28f44d8c59e155c98d3 100644 (file)
--- a/src/librustc/infer/sub.rs
+++ b/src/librustc/infer/sub.rs
@@ -130,7 +130,7 @@ fn regions(&mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>)
         // FIXME -- we have more fine-grained information available
         // from the "cause" field, we could perhaps give more tailored
         // error messages.
-        let origin = SubregionOrigin::Subtype(self.fields.trace.clone());
+        let origin = SubregionOrigin::Subtype(box self.fields.trace.clone());
         self.fields.infcx.borrow_region_constraints()
                          .make_subregion(origin, a, b);