ci: make changes to riscv64-linux to try to avoid timeouts

The idea is to have 2 runners per machine, since a lot of time is spent building
stage3 and stage4, both of which are largely single-core affairs. This will make
the test steps take longer, however, so the timeouts have been bumped a bit, and
max RSS for the test step has been lowered from 64G to 32G to prevent OOM.
Finally, we now only run a single ReleaseSafe job on PRs; Debug and Release jobs
are limited to pushes.

.github/workflows/ci.yaml

@@ -51,7 +51,8 @@ jobs:
       - name: Build and Test
         run: sh ci/aarch64-linux-release.sh
   riscv64-linux-debug:
-    timeout-minutes: 900
+    if: ${{ github.event_name == 'push' }}
+    timeout-minutes: 1020
     runs-on: [self-hosted, Linux, riscv64]
     steps:
       - name: Checkout
@@ -59,13 +60,23 @@ jobs:
       - name: Build and Test
         run: sh ci/riscv64-linux-debug.sh
   riscv64-linux-release:
-    timeout-minutes: 780
+    if: ${{ github.event_name == 'push' }}
+    timeout-minutes: 900
     runs-on: [self-hosted, Linux, riscv64]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Build and Test
         run: sh ci/riscv64-linux-release.sh
+  riscv64-linux-releasesafe:
+    if: ${{ github.event_name == 'pull_request' }}
+    timeout-minutes: 900
+    runs-on: [self-hosted, Linux, riscv64]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Build and Test
+        run: sh ci/riscv64-linux-releasesafe.sh
   x86_64-macos-release:
     runs-on: "macos-13"
     env:

ci/riscv64-linux-debug.sh

@@ -50,7 +50,7 @@ ninja install
 
 # No -fqemu and -fwasmtime here as they're covered by the x86_64-linux scripts.
 stage3-debug/bin/zig build test docs \
-  --maxrss 68719476736 \
+  --maxrss 34359738368 \
   -Dstatic-llvm \
   -Dskip-non-native \
   -Dtarget=native-native-musl \

ci/riscv64-linux-release.sh

@@ -50,7 +50,7 @@ ninja install
 
 # No -fqemu and -fwasmtime here as they're covered by the x86_64-linux scripts.
 stage3-release/bin/zig build test docs \
-  --maxrss 68719476736 \
+  --maxrss 34359738368 \
   -Dstatic-llvm \
   -Dskip-non-native \
   -Dtarget=native-native-musl \

ci/riscv64-linux-releasesafe.sh

@@ -0,0 +1,76 @@
+#!/bin/sh
+
+# Requires cmake ninja-build
+
+set -x
+set -e
+
+ARCH="$(uname -m)"
+TARGET="$ARCH-linux-musl"
+MCPU="spacemit_x60"
+CACHE_BASENAME="zig+llvm+lld+clang-riscv64-linux-musl-0.15.0-dev.929+31e46be74"
+PREFIX="$HOME/deps/$CACHE_BASENAME"
+ZIG="$PREFIX/bin/zig"
+
+export PATH="$HOME/local/bin:$PATH"
+
+# Make the `zig version` number consistent.
+# This will affect the cmake command below.
+git fetch --unshallow || true
+git fetch --tags
+
+# Override the cache directories because they won't actually help other CI runs
+# which will be testing alternate versions of zig, and ultimately would just
+# fill up space on the hard drive for no reason.
+export ZIG_GLOBAL_CACHE_DIR="$PWD/zig-global-cache"
+export ZIG_LOCAL_CACHE_DIR="$PWD/zig-local-cache"
+
+mkdir build-releasesafe
+cd build-releasesafe
+
+export CC="$ZIG cc -target $TARGET -mcpu=$MCPU"
+export CXX="$ZIG c++ -target $TARGET -mcpu=$MCPU"
+
+cmake .. \
+  -DCMAKE_INSTALL_PREFIX="stage3-releasesafe" \
+  -DCMAKE_PREFIX_PATH="$PREFIX" \
+  -DCMAKE_BUILD_TYPE=Release \
+  -DZIG_RELEASE_SAFE=ON \
+  -DZIG_TARGET_TRIPLE="$TARGET" \
+  -DZIG_TARGET_MCPU="$MCPU" \
+  -DZIG_STATIC=ON \
+  -DZIG_NO_LIB=ON \
+  -GNinja
+
+# Now cmake will use zig as the C/C++ compiler. We reset the environment variables
+# so that installation and testing do not get affected by them.
+unset CC
+unset CXX
+
+ninja install
+
+# No -fqemu and -fwasmtime here as they're covered by the x86_64-linux scripts.
+stage3-releasesafe/bin/zig build test docs \
+  --maxrss 34359738368 \
+  -Dstatic-llvm \
+  -Dskip-non-native \
+  -Dtarget=native-native-musl \
+  --search-prefix "$PREFIX" \
+  --zig-lib-dir "$PWD/../lib"
+
+# Ensure that stage3 and stage4 are byte-for-byte identical.
+stage3-releasesafe/bin/zig build \
+  --prefix stage4-releasesafe \
+  -Denable-llvm \
+  -Dno-lib \
+  -Doptimize=ReleaseSafe \
+  -Dstrip \
+  -Dtarget=$TARGET \
+  -Dcpu=$MCPU \
+  -Duse-zig-libcxx \
+  -Dversion-string="$(stage3-releasesafe/bin/zig version)"
+
+# diff returns an error code if the files differ.
+echo "If the following command fails, it means nondeterminism has been"
+echo "introduced, making stage3 and stage4 no longer byte-for-byte identical."
+diff stage3-releasesafe/bin/zig stage4-releasesafe/bin/zig