From 446798f84ba0f0f9fe4c79a65256f5920ef2f4ac Mon Sep 17 00:00:00 2001
From: Lzu Tao <taolzu@gmail.com>
Date: Mon, 8 Feb 2021 05:06:49 +0000
Subject: [PATCH 1/2] fix bootstrap

---
 src/bootstrap/builder.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index f1a160250dbe1..0f5fcb4af400d 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1490,7 +1490,7 @@ impl<'a> Builder<'a> {
                 for el in stack.iter().rev() {
                     out += &format!("\t{:?}\n", el);
                 }
-                panic!(out);
+                panic!("{}", out);
             }
             if let Some(out) = self.cache.get(&step) {
                 self.verbose(&format!("{}c {:?}", "  ".repeat(stack.len()), step));

From 010e194d6e7e0349518fb2bdb4c4a09a395dfce5 Mon Sep 17 00:00:00 2001
From: Lzu Tao <taolzu@gmail.com>
Date: Mon, 8 Feb 2021 05:01:02 +0000
Subject: [PATCH 2/2] Specialize slice::fill for Copy type and u8/i8/bool

---
 library/core/src/slice/mod.rs        |  9 +----
 library/core/src/slice/specialize.rs | 58 ++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+), 7 deletions(-)
 create mode 100644 library/core/src/slice/specialize.rs

diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 19a3b45e568c0..7db9c42921241 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -34,6 +34,7 @@ mod iter;
 mod raw;
 mod rotate;
 mod sort;
+mod specialize;
 
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use iter::{Chunks, ChunksMut, Windows};
@@ -2831,13 +2832,7 @@ impl<T> [T] {
     where
         T: Clone,
     {
-        if let Some((last, elems)) = self.split_last_mut() {
-            for el in elems {
-                el.clone_from(&value);
-            }
-
-            *last = value
-        }
+        specialize::SpecFill::spec_fill(self, value);
     }
 
     /// Fills `self` with elements returned by calling a closure repeatedly.
diff --git a/library/core/src/slice/specialize.rs b/library/core/src/slice/specialize.rs
new file mode 100644
index 0000000000000..16a9588989c85
--- /dev/null
+++ b/library/core/src/slice/specialize.rs
@@ -0,0 +1,58 @@
+use crate::ptr::write_bytes;
+
+pub(super) trait SpecFill<T> {
+    fn spec_fill(&mut self, value: T);
+}
+
+impl<T: Clone> SpecFill<T> for [T] {
+    default fn spec_fill(&mut self, value: T) {
+        if let Some((last, elems)) = self.split_last_mut() {
+            for el in elems {
+                el.clone_from(&value);
+            }
+
+            *last = value
+        }
+    }
+}
+
+impl<T: Copy> SpecFill<T> for [T] {
+    default fn spec_fill(&mut self, value: T) {
+        for item in self.iter_mut() {
+            *item = value;
+        }
+    }
+}
+
+impl SpecFill<u8> for [u8] {
+    fn spec_fill(&mut self, value: u8) {
+        // SAFETY: this is slice of u8
+        unsafe {
+            let ptr = self.as_mut_ptr();
+            let len = self.len();
+            write_bytes(ptr, value, len);
+        }
+    }
+}
+
+impl SpecFill<i8> for [i8] {
+    fn spec_fill(&mut self, value: i8) {
+        // SAFETY: this is slice of i8
+        unsafe {
+            let ptr = self.as_mut_ptr();
+            let len = self.len();
+            write_bytes(ptr, value as u8, len);
+        }
+    }
+}
+
+impl SpecFill<bool> for [bool] {
+    fn spec_fill(&mut self, value: bool) {
+        // SAFETY: this is slice of bool
+        unsafe {
+            let ptr = self.as_mut_ptr();
+            let len = self.len();
+            write_bytes(ptr, value as u8, len);
+        }
+    }
+}