Update to Rust 1.43.0.

We unfortunately have to add a patch to fix
rust-lang/rust#69352.

Author: jgalenson

patches/rustc-0001-Revert-Change-opt-level-from-2-back-to-3.patch

@@ -0,0 +1,60 @@
+From 00ab608642b2b7f8a1dfa4b04958c5188c71cff8 Mon Sep 17 00:00:00 2001
+From: Joel Galenson <[email protected]>
+Date: Thu, 23 Apr 2020 12:43:32 -0700
+Subject: [PATCH] Revert "Change opt-level from 2 back to 3"
+
+This reverts commit 0d52c562db18e85cf53078c9ddb40abe469a4aab.
+---
+ Cargo.toml                                           | 7 +++++++
+ src/librustc_mir/interpret/step.rs                   | 3 ---
+ src/test/run-make/wasm-stringify-ints-small/Makefile | 2 +-
+ 3 files changed, 8 insertions(+), 4 deletions(-)
+
+diff --git a/Cargo.toml b/Cargo.toml
+index 2f5a708e8dc..9d5c27b96df 100644
+--- a/Cargo.toml
++++ b/Cargo.toml
+@@ -31,6 +31,13 @@ exclude = [
+   "obj",
+ ]
+ 
++# Curiously, LLVM 7.0 will segfault if compiled with opt-level=3
++# See issue https://github.com/rust-lang/rust/issues/52378
++[profile.release]
++opt-level = 2
++[profile.bench]
++opt-level = 2
++
+ # These options are controlled from our rustc wrapper script, so turn them off
+ # here and have them controlled elsewhere.
+ [profile.dev]
+diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
+index f298a6677d6..4a3f4d9b14e 100644
+--- a/src/librustc_mir/interpret/step.rs
++++ b/src/librustc_mir/interpret/step.rs
+@@ -38,9 +38,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
+     /// Returns `true` as long as there are more things to do.
+     ///
+     /// This is used by [priroda](https://github.com/oli-obk/priroda)
+-    ///
+-    /// This is marked `#inline(always)` to work around adverserial codegen when `opt-level = 3`
+-    #[inline(always)]
+     pub fn step(&mut self) -> InterpResult<'tcx, bool> {
+         if self.stack.is_empty() {
+             return Ok(false);
+diff --git a/src/test/run-make/wasm-stringify-ints-small/Makefile b/src/test/run-make/wasm-stringify-ints-small/Makefile
+index 01e1c6b0ce8..26de6a0c689 100644
+--- a/src/test/run-make/wasm-stringify-ints-small/Makefile
++++ b/src/test/run-make/wasm-stringify-ints-small/Makefile
+@@ -4,7 +4,7 @@ ifeq ($(TARGET),wasm32-unknown-unknown)
+ all:
+ 	$(RUSTC) foo.rs -C lto -O --target wasm32-unknown-unknown
+ 	wc -c < $(TMPDIR)/foo.wasm
+-	[ "`wc -c < $(TMPDIR)/foo.wasm`" -lt "25000" ]
++	[ "`wc -c < $(TMPDIR)/foo.wasm`" -lt "20500" ]
+ else
+ all:
+ endif
+-- 
+2.26.2.303.gf8c07b1a785-goog
+

repro.sh

@@ -11,14 +11,14 @@ compile() {
 
 # Dowload and setup Cargo with our patches.
 if [ ! -d cargo ]; then
-    git clone --branch rust-1.42.0 https://github.com/rust-lang/cargo.git
+    git clone --branch rust-1.43.0 https://github.com/rust-lang/cargo.git
     # Apply the patch.
     git -C cargo apply ${PWD}/patches/cargo*
 fi
 
 # Download and set up the two rustc directories with our patches.
 if [ ! -d rust-a ]; then
-    git clone --branch 1.42.0 https://github.com/rust-lang/rust.git rust-a
+    git clone --branch 1.43.0 https://github.com/rust-lang/rust.git rust-a
     # Run x.py and do nothing so it downloads LLVM and other tools.
     cd rust-a
     ./x.py