From c9b3b688d5121d155cb29df78d83ce1b9cc19a98 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sat, 30 Nov 2019 10:06:12 +0100
Subject: [PATCH 1/4] add toolchain mgmt script

---
 CONTRIBUTING.md | 46 +++++++++++++++++++---------------------------
 toolchain       | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 27 deletions(-)
 create mode 100755 toolchain

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d6436873938e..9338f0b8dd73 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -12,6 +12,22 @@ on the [Rust Zulip].
 
 [Rust Zulip]: https://rust-lang.zulipchat.com
 
+## Building Miri with a pre-built rustc
+
+Miri heavily relies on internal rustc interfaces to execute MIR.  Still, some
+things (like adding support for a new intrinsic or a shim for an external
+function being called) can be done by working just on the Miri side.
+
+The `rust-version` file contains the commit hash of rustc that Miri is currently
+tested against. Other versions will likely not work. After installing
+[`rustup-toolchain-install-master`], you can run the following command to
+install that exact version of rustc as a toolchain:
+```
+./toolchain
+```
+
+[`rustup-toolchain-install-master`]: https://github.com/kennytm/rustup-toolchain-install-master
+
 ### Fixing Miri when rustc changes
 
 Miri is heavily tied to rustc internals, so it is very common that rustc changes
@@ -20,36 +36,12 @@ Usually, Miri will require changes similar to the other consumers of the changed
 rustc API, so reading the rustc PR diff is a good way to get an idea for what is
 needed.
 
-When submitting a PR against Miri after fixing it for rustc changes, make sure
-you update the `rust-version` file.  That file always contains the exact rustc
-git commit with which Miri works, and it is the version that our CI tests Miri
-against.
-
-## Building Miri with a nightly rustc
-
-Miri heavily relies on internal rustc interfaces to execute MIR.  Still, some
-things (like adding support for a new intrinsic or a shim for an external
-function being called) can be done by working just on the Miri side.
-
-To prepare, make sure you are using a nightly Rust compiler.  You also need to
-have the `rust-src` and `rustc-dev` components installed, which you can add via
-`rustup component add rust-src rustc-dev`.  Then you should be able to just
-`cargo build` Miri.
-
-In case this fails, your nightly might be incompatible with Miri master.  The
-`rust-version` file contains the commit hash of rustc that Miri is currently
-tested against; you can use that to find a nightly that works or you might have
-to wait for the next nightly to get released. You can also use
-[`rustup-toolchain-install-master`](https://github.com/kennytm/rustup-toolchain-install-master)
-to install that exact version of rustc as a toolchain:
+To update the `rustc-version` file and install the latest rustc, you can run:
 ```
-rustup-toolchain-install-master $(cat rust-version) -c rust-src -c rustc-dev
+./toolchain HEAD
 ```
 
-Another common problem is outdated dependencies: Miri does not come with a
-lockfile (it cannot, due to how it gets embedded into the rustc build). So you
-have to run `cargo update` every now and then yourself to make sure you are
-using the latest versions of everything (which is what gets tested on CI).
+Now try `./miri test`, and submit a PR once that works again.
 
 ## Testing the Miri driver
 [testing-miri]: #testing-the-miri-driver
diff --git a/toolchain b/toolchain
new file mode 100755
index 000000000000..043b2ee2edd7
--- /dev/null
+++ b/toolchain
@@ -0,0 +1,40 @@
+#!/bin/bash
+set -e
+# Manages a rustup toolchain called "miri".
+#
+# All commands set "miri" as the override toolchain for the current directory,
+# and make the `rust-version` file match that toolchain.
+#
+# USAGE:
+#
+# ./toolchain: Update "miri" toolchain to match `rust-version` (the known-good version for this commit).
+# 
+# ./toolchain HEAD: Update "miri" toolchain and `rust-version` file to latest rustc HEAD.
+# 
+# ./toolchain $COMMIT: Update "miri" toolchain and `rust-version` file to match that commit.
+
+# Determine new commit.
+if [[ "$1" == "" ]]; then
+    NEW_COMMIT=$(cat rust-version)
+elif [[ "$1" == "HEAD" ]]; then
+    NEW_COMMIT=$(git ls-remote https://github.com/rust-lang/rust/ HEAD | cut -f 1)
+else
+    NEW_COMMIT="$1"
+fi
+echo "$NEW_COMMIT" > rust-version
+
+# Check if we already are at that commit.
+CUR_COMMIT=$(rustc +miri --version -v | egrep "^commit-hash: " | cut -d " " -f 2)
+if [[ "$CUR_COMMIT" == "$NEW_COMMIT" ]]; then
+    echo "miri toolchain is already at commit $CUR_COMMIT."
+    rustup override set miri
+    exit 0
+fi
+
+# Cleanup.
+cargo +nightly clean # Use nightly cargo as miri toolchain might be broken.
+rustup toolchain uninstall miri
+
+# Install and setup new toolchain.
+rustup-toolchain-install-master -n miri -c rust-src -c rustc-dev -- "$NEW_COMMIT"
+rustup override set miri

From f838410f492690e09626e9ae95f110f948235dce Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 1 Dec 2019 10:20:16 +0100
Subject: [PATCH 2/4] toolchain -> rustup-toolchain

---
 CONTRIBUTING.md               | 4 ++--
 toolchain => rustup-toolchain | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)
 rename toolchain => rustup-toolchain (76%)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 9338f0b8dd73..c673e107d55d 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -23,7 +23,7 @@ tested against. Other versions will likely not work. After installing
 [`rustup-toolchain-install-master`], you can run the following command to
 install that exact version of rustc as a toolchain:
 ```
-./toolchain
+./rustup-toolchain
 ```
 
 [`rustup-toolchain-install-master`]: https://github.com/kennytm/rustup-toolchain-install-master
@@ -38,7 +38,7 @@ needed.
 
 To update the `rustc-version` file and install the latest rustc, you can run:
 ```
-./toolchain HEAD
+./rustup-toolchain HEAD
 ```
 
 Now try `./miri test`, and submit a PR once that works again.
diff --git a/toolchain b/rustup-toolchain
similarity index 76%
rename from toolchain
rename to rustup-toolchain
index 043b2ee2edd7..a981ec76548a 100755
--- a/toolchain
+++ b/rustup-toolchain
@@ -7,11 +7,11 @@ set -e
 #
 # USAGE:
 #
-# ./toolchain: Update "miri" toolchain to match `rust-version` (the known-good version for this commit).
+# ./rustup-toolchain: Update "miri" toolchain to match `rust-version` (the known-good version for this commit).
 # 
-# ./toolchain HEAD: Update "miri" toolchain and `rust-version` file to latest rustc HEAD.
+# ./rustup-toolchain HEAD: Update "miri" toolchain and `rust-version` file to latest rustc HEAD.
 # 
-# ./toolchain $COMMIT: Update "miri" toolchain and `rust-version` file to match that commit.
+# ./rustup-toolchain $COMMIT: Update "miri" toolchain and `rust-version` file to match that commit.
 
 # Determine new commit.
 if [[ "$1" == "" ]]; then

From 0a4ec5d34e542ff00ff41110b0fc42072bd1b4aa Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 1 Dec 2019 10:22:16 +0100
Subject: [PATCH 3/4] test for rustup-toolchain-install-master

---
 rustup-toolchain | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rustup-toolchain b/rustup-toolchain
index a981ec76548a..096fa8857bab 100755
--- a/rustup-toolchain
+++ b/rustup-toolchain
@@ -13,6 +13,12 @@ set -e
 # 
 # ./rustup-toolchain $COMMIT: Update "miri" toolchain and `rust-version` file to match that commit.
 
+# Make sure rustup-toolchain-install-master is installed.
+if ! which rustup-toolchain-install-master >/dev/null; then
+    echo "Please install rustup-toolchain-install-master by running 'cargo install rustup-toolchain-install-master'"
+    exit 1
+fi
+
 # Determine new commit.
 if [[ "$1" == "" ]]; then
     NEW_COMMIT=$(cat rust-version)

From 9501d044c1afcd2c7921e48ef17930977d156dec Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 1 Dec 2019 15:16:55 +0100
Subject: [PATCH 4/4] don't assume a nightly toolchain is installed

---
 rustup-toolchain | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/rustup-toolchain b/rustup-toolchain
index 096fa8857bab..4e8e0b01ebc4 100755
--- a/rustup-toolchain
+++ b/rustup-toolchain
@@ -30,17 +30,17 @@ fi
 echo "$NEW_COMMIT" > rust-version
 
 # Check if we already are at that commit.
-CUR_COMMIT=$(rustc +miri --version -v | egrep "^commit-hash: " | cut -d " " -f 2)
+CUR_COMMIT=$(rustc +miri --version -v 2>/dev/null | egrep "^commit-hash: " | cut -d " " -f 2)
 if [[ "$CUR_COMMIT" == "$NEW_COMMIT" ]]; then
     echo "miri toolchain is already at commit $CUR_COMMIT."
     rustup override set miri
     exit 0
 fi
 
-# Cleanup.
-cargo +nightly clean # Use nightly cargo as miri toolchain might be broken.
-rustup toolchain uninstall miri
-
 # Install and setup new toolchain.
+rustup toolchain uninstall miri
 rustup-toolchain-install-master -n miri -c rust-src -c rustc-dev -- "$NEW_COMMIT"
 rustup override set miri
+
+# Cleanup.
+cargo clean