Micro-optimize

Author: saethlin

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -250,6 +250,7 @@ impl<'a, 'tcx> Metadata<'a, 'tcx> for (CrateMetadataRef<'a>, TyCtxt<'tcx>) {
 }
 
 impl<T: ParameterizedOverTcx> LazyValue<T> {
+    #[inline]
     fn decode<'a, 'tcx, M: Metadata<'a, 'tcx>>(self, metadata: M) -> T::Value<'tcx>
     where
         T::Value<'tcx>: Decodable<DecodeContext<'a, 'tcx>>,
@@ -294,6 +295,7 @@ unsafe impl<'a, 'tcx, T: Decodable<DecodeContext<'a, 'tcx>>> TrustedLen
 }
 
 impl<T: ParameterizedOverTcx> LazyArray<T> {
+    #[inline]
     fn decode<'a, 'tcx, M: Metadata<'a, 'tcx>>(
         self,
         metadata: M,
@@ -420,25 +422,29 @@ impl<'a, 'tcx> TyDecoder for DecodeContext<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for CrateNum {
+    #[inline]
     fn decode(d: &mut DecodeContext<'a, 'tcx>) -> CrateNum {
         let cnum = CrateNum::from_u32(d.read_u32());
         d.map_encoded_cnum_to_current(cnum)
     }
 }
 
 impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for DefIndex {
+    #[inline]
     fn decode(d: &mut DecodeContext<'a, 'tcx>) -> DefIndex {
         DefIndex::from_u32(d.read_u32())
     }
 }
 
 impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for ExpnIndex {
+    #[inline]
     fn decode(d: &mut DecodeContext<'a, 'tcx>) -> ExpnIndex {
         ExpnIndex::from_u32(d.read_u32())
     }
 }
 
 impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for ast::AttrId {
+    #[inline]
     fn decode(d: &mut DecodeContext<'a, 'tcx>) -> ast::AttrId {
         let sess = d.sess.expect("can't decode AttrId without Session");
         sess.parse_sess.attr_id_generator.mk_attr_id()
@@ -657,6 +663,7 @@ impl<'a, 'tcx, T> Decodable<DecodeContext<'a, 'tcx>> for LazyValue<T> {
 }
 
 impl<'a, 'tcx, T> Decodable<DecodeContext<'a, 'tcx>> for LazyArray<T> {
+    #[inline]
     fn decode(decoder: &mut DecodeContext<'a, 'tcx>) -> Self {
         let len = decoder.read_usize();
         if len == 0 { LazyArray::default() } else { decoder.read_lazy_array(len) }

compiler/rustc_metadata/src/rmeta/table.rs

@@ -480,7 +480,6 @@ where
     for<'tcx> T::Value<'tcx>: FixedSizeEncoding<ByteArray = [u8; N]>,
 {
     /// Given the metadata, extract out the value at a particular index (if any).
-    #[inline(never)]
     pub(super) fn get<'a, 'tcx, M: Metadata<'a, 'tcx>>(&self, metadata: M, i: I) -> T::Value<'tcx> {
         trace!("LazyTable::lookup: index={:?} len={:?}", i, self.len);
 
@@ -494,9 +493,13 @@ where
         let end = start + width;
         let bytes = &metadata.blob()[start..end];
 
-        let mut fixed = [0u8; N];
-        fixed[..width].copy_from_slice(bytes);
-        FixedSizeEncoding::from_bytes(&fixed)
+        if let Ok(fixed) = bytes.try_into() {
+            FixedSizeEncoding::from_bytes(fixed)
+        } else {
+            let mut fixed = [0u8; N];
+            fixed[..width].copy_from_slice(bytes);
+            FixedSizeEncoding::from_bytes(&fixed)
+        }
     }
 
     /// Size of the table in entries, including possible gaps.