Rollup of 9 pull requests

.azure-pipelines/steps/run.yml

@@ -11,6 +11,12 @@ steps:
 - checkout: self
   fetchDepth: 2
 
+# Spawn a background process to collect CPU usage statistics which we'll upload
+# at the end of the build. See the comments in the script here for more
+# information.
+- bash: python src/ci/cpu-usage-over-time.py &> cpu-usage.csv &
+  displayName: "Collect CPU-usage statistics in the background"
+
 - bash: printenv | sort
   displayName: Show environment variables
 
@@ -142,3 +148,13 @@ steps:
     AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
   condition: and(succeeded(), or(eq(variables.DEPLOY, '1'), eq(variables.DEPLOY_ALT, '1')))
   displayName: Upload artifacts
+
+# Upload CPU usage statistics that we've been gathering this whole time. Always
+# execute this step in case we want to inspect failed builds, but don't let
+# errors here ever fail the build since this is just informational.
+- bash: aws s3 cp --acl public-read cpu-usage.csv s3://$DEPLOY_BUCKET/rustc-builds/$BUILD_SOURCEVERSION/cpu-$SYSTEM_JOBNAME.csv
+  env:
+    AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
+  condition: contains(variables, 'AWS_SECRET_ACCESS_KEY')
+  continueOnError: true
+  displayName: Upload CPU usage statistics

Cargo.lock

@@ -910,6 +910,9 @@ dependencies = [
 [[package]]
 name = "fmt_macros"
 version = "0.0.0"
+dependencies = [
+ "syntax_pos 0.0.0",
+]
 
 [[package]]
 name = "fnv"

src/bootstrap/doc.rs

@@ -64,7 +64,7 @@ book!(
     EmbeddedBook, "src/doc/embedded-book", "embedded-book", RustbookVersion::MdBook2;
     Nomicon, "src/doc/nomicon", "nomicon", RustbookVersion::MdBook2;
     Reference, "src/doc/reference", "reference", RustbookVersion::MdBook1;
-    RustByExample, "src/doc/rust-by-example", "rust-by-example", RustbookVersion::MdBook1;
+    RustByExample, "src/doc/rust-by-example", "rust-by-example", RustbookVersion::MdBook2;
     RustcBook, "src/doc/rustc", "rustc", RustbookVersion::MdBook1;
     RustdocBook, "src/doc/rustdoc", "rustdoc", RustbookVersion::MdBook2;
 );

src/bootstrap/native.rs

@@ -416,7 +416,7 @@ fn configure_cmake(builder: &Builder<'_>,
 
     cfg.build_arg("-j").build_arg(builder.jobs().to_string());
     let mut cflags = builder.cflags(target, GitRepo::Llvm).join(" ");
-    if let Some(ref s) = builder.config.llvm_cxxflags {
+    if let Some(ref s) = builder.config.llvm_cflags {
         cflags.push_str(&format!(" {}", s));
     }
     cfg.define("CMAKE_C_FLAGS", cflags);

src/ci/cpu-usage-over-time.py

@@ -0,0 +1,175 @@
+#!/usr/bin/env python
+# ignore-tidy-linelength
+
+# This is a small script that we use on CI to collect CPU usage statistics of
+# our builders. By seeing graphs of CPU usage over time we hope to correlate
+# that with possible improvements to Rust's own build system, ideally diagnosing
+# that either builders are always fully using their CPU resources or they're
+# idle for long stretches of time.
+#
+# This script is relatively simple, but it's platform specific. Each platform
+# (OSX/Windows/Linux) has a different way of calculating the current state of
+# CPU at a point in time. We then compare two captured states to determine the
+# percentage of time spent in one state versus another. The state capturing is
+# all platform-specific but the loop at the bottom is the cross platform part
+# that executes everywhere.
+#
+# # Viewing statistics
+#
+# All builders will upload their CPU statistics as CSV files to our S3 buckets.
+# These URLS look like:
+#
+#   https://$bucket.s3.amazonaws.com/rustc-builds/$commit/cpu-$builder.csv
+#
+# for example
+#
+#   https://rust-lang-ci2.s3.amazonaws.com/rustc-builds/68baada19cd5340f05f0db15a3e16d6671609bcc/cpu-x86_64-apple.csv
+#
+# Each CSV file has two columns. The first is the timestamp of the measurement
+# and the second column is the % of idle cpu time in that time slice. Ideally
+# the second column is always zero.
+#
+# Once you've downloaded a file there's various ways to plot it and visualize
+# it. For command line usage you can use a script like so:
+#
+#      set timefmt '%Y-%m-%dT%H:%M:%S'
+#      set xdata time
+#      set ylabel "Idle CPU %"
+#      set xlabel "Time"
+#      set datafile sep ','
+#      set term png
+#      set output "printme.png"
+#      set grid
+#      builder = "i686-apple"
+#      plot "cpu-".builder.".csv" using 1:2 with lines title builder
+#
+# Executed as `gnuplot < ./foo.plot` it will generate a graph called
+# `printme.png` which you can then open up. If you know how to improve this
+# script or the viewing process that would be much appreciated :) (or even if
+# you know how to automate it!)
+
+import datetime
+import sys
+import time
+
+if sys.platform == 'linux2':
+    class State:
+        def __init__(self):
+            with open('/proc/stat', 'r') as file:
+                data = file.readline().split()
+            if data[0] != 'cpu':
+                raise Exception('did not start with "cpu"')
+            self.user = int(data[1])
+            self.nice = int(data[2])
+            self.system = int(data[3])
+            self.idle = int(data[4])
+            self.iowait = int(data[5])
+            self.irq = int(data[6])
+            self.softirq = int(data[7])
+            self.steal = int(data[8])
+            self.guest = int(data[9])
+            self.guest_nice = int(data[10])
+
+        def idle_since(self, prev):
+            user = self.user - prev.user
+            nice = self.nice - prev.nice
+            system = self.system - prev.system
+            idle = self.idle - prev.idle
+            iowait = self.iowait - prev.iowait
+            irq = self.irq - prev.irq
+            softirq = self.softirq - prev.softirq
+            steal = self.steal - prev.steal
+            guest = self.guest - prev.guest
+            guest_nice = self.guest_nice - prev.guest_nice
+            total = user + nice + system + idle + iowait + irq + softirq + steal + guest + guest_nice
+            return float(idle) / float(total) * 100
+
+elif sys.platform == 'win32':
+    from ctypes.wintypes import DWORD
+    from ctypes import Structure, windll, WinError, GetLastError, byref
+
+    class FILETIME(Structure):
+        _fields_ = [
+            ("dwLowDateTime", DWORD),
+            ("dwHighDateTime", DWORD),
+        ]
+
+    class State:
+        def __init__(self):
+            idle, kernel, user = FILETIME(), FILETIME(), FILETIME()
+
+            success = windll.kernel32.GetSystemTimes(
+                byref(idle),
+                byref(kernel),
+                byref(user),
+            )
+
+            assert success, WinError(GetLastError())[1]
+
+            self.idle = (idle.dwHighDateTime << 32) | idle.dwLowDateTime
+            self.kernel = (kernel.dwHighDateTime << 32) | kernel.dwLowDateTime
+            self.user = (user.dwHighDateTime << 32) | user.dwLowDateTime
+
+        def idle_since(self, prev):
+            idle = self.idle - prev.idle
+            user = self.user - prev.user
+            kernel = self.kernel - prev.kernel
+            return float(idle) / float(user + kernel) * 100
+
+elif sys.platform == 'darwin':
+    from ctypes import *
+    libc = cdll.LoadLibrary('/usr/lib/libc.dylib')
+
+    PROESSOR_CPU_LOAD_INFO = c_int(2)
+    CPU_STATE_USER = 0
+    CPU_STATE_SYSTEM = 1
+    CPU_STATE_IDLE = 2
+    CPU_STATE_NICE = 3
+    c_int_p = POINTER(c_int)
+
+    class State:
+        def __init__(self):
+            num_cpus_u = c_uint(0)
+            cpu_info = c_int_p()
+            cpu_info_cnt = c_int(0)
+            err = libc.host_processor_info(
+                libc.mach_host_self(),
+                PROESSOR_CPU_LOAD_INFO,
+                byref(num_cpus_u),
+                byref(cpu_info),
+                byref(cpu_info_cnt),
+            )
+            assert err == 0
+            self.user = 0
+            self.system = 0
+            self.idle = 0
+            self.nice = 0
+            cur = 0
+            while cur < cpu_info_cnt.value:
+                self.user += cpu_info[cur + CPU_STATE_USER]
+                self.system += cpu_info[cur + CPU_STATE_SYSTEM]
+                self.idle += cpu_info[cur + CPU_STATE_IDLE]
+                self.nice += cpu_info[cur + CPU_STATE_NICE]
+                cur += num_cpus_u.value
+
+        def idle_since(self, prev):
+            user = self.user - prev.user
+            system = self.system - prev.system
+            idle = self.idle - prev.idle
+            nice = self.nice - prev.nice
+            return float(idle) / float(user + system + idle + nice) * 100.0
+
+else:
+    print('unknown platform', sys.platform)
+    sys.exit(1)
+
+cur_state = State();
+print("Time,Idle")
+while True:
+    time.sleep(1);
+    next_state = State();
+    now = datetime.datetime.utcnow().isoformat()
+    idle = next_state.idle_since(cur_state)
+    print("%s,%s" % (now, idle))
+    sys.stdout.flush()
+    cur_state = next_state

src/libcore/iter/range.rs

@@ -281,6 +281,19 @@ impl<A: Step> DoubleEndedIterator for ops::Range<A> {
             None
         }
     }
+
+    #[inline]
+    fn nth_back(&mut self, n: usize) -> Option<A> {
+        if let Some(minus_n) = self.end.sub_usize(n) {
+            if minus_n > self.start {
+                self.end = minus_n.sub_one();
+                return Some(self.end.clone())
+            }
+        }
+
+        self.end = self.start.clone();
+        None
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -438,6 +451,34 @@ impl<A: Step> DoubleEndedIterator for ops::RangeInclusive<A> {
         })
     }
 
+    #[inline]
+    fn nth_back(&mut self, n: usize) -> Option<A> {
+        self.compute_is_empty();
+        if self.is_empty.unwrap_or_default() {
+            return None;
+        }
+
+        if let Some(minus_n) = self.end.sub_usize(n) {
+            use crate::cmp::Ordering::*;
+
+            match minus_n.partial_cmp(&self.start) {
+                Some(Greater) => {
+                    self.is_empty = Some(false);
+                    self.end = minus_n.sub_one();
+                    return Some(minus_n);
+                }
+                Some(Equal) => {
+                    self.is_empty = Some(true);
+                    return Some(minus_n);
+                }
+                _ => {}
+            }
+        }
+
+        self.is_empty = Some(true);
+        None
+    }
+
     #[inline]
     fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
         Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>

src/libcore/option.rs

@@ -145,7 +145,7 @@ use crate::pin::Pin;
 // which basically means it must be `Option`.
 
 /// The `Option` type. See [the module level documentation](index.html) for more.
-#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
+#[derive(Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub enum Option<T> {
     /// No value
@@ -1040,6 +1040,25 @@ fn expect_failed(msg: &str) -> ! {
 // Trait implementations
 /////////////////////////////////////////////////////////////////////////////
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Clone> Clone for Option<T> {
+    #[inline]
+    fn clone(&self) -> Self {
+        match self {
+            Some(x) => Some(x.clone()),
+            None => None,
+        }
+    }
+
+    #[inline]
+    fn clone_from(&mut self, source: &Self) {
+        match (self, source) {
+            (Some(to), Some(from)) => to.clone_from(from),
+            (to, from) => *to = from.clone(),
+        }
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Default for Option<T> {
     /// Returns [`None`][Option::None].

src/libcore/result.rs

@@ -240,7 +240,7 @@ use crate::ops::{self, Deref};
 ///
 /// [`Ok`]: enum.Result.html#variant.Ok
 /// [`Err`]: enum.Result.html#variant.Err
-#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
+#[derive(Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 #[must_use = "this `Result` may be an `Err` variant, which should be handled"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub enum Result<T, E> {
@@ -1003,6 +1003,27 @@ fn unwrap_failed<E: fmt::Debug>(msg: &str, error: E) -> ! {
 // Trait implementations
 /////////////////////////////////////////////////////////////////////////////
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Clone, E: Clone> Clone for Result<T, E> {
+    #[inline]
+    fn clone(&self) -> Self {
+        match self {
+            Ok(x) => Ok(x.clone()),
+            Err(x) => Err(x.clone()),
+        }
+    }
+
+    #[inline]
+    fn clone_from(&mut self, source: &Self) {
+        match (self, source) {
+            (Ok(to), Ok(from)) => to.clone_from(from),
+            (Err(to), Err(from)) => to.clone_from(from),
+            (to, from) => *to = from.clone(),
+        }
+    }
+}
+
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, E> IntoIterator for Result<T, E> {
     type Item = T;