diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
new file mode 100644
index 00000000000000..e1d1c02755939b
--- /dev/null
+++ b/.github/workflows/ci-tests.yml
@@ -0,0 +1,156 @@
+name: "CI Tests"
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      # When a PR is closed, we still start this workflow, but then skip
+      # all the jobs, which makes it effectively a no-op.  The reason to
+      # do this is that it allows us to take advantage of concurrency groups
+      # to cancel in progress CI jobs whenever the PR is closed.
+      - closed
+    branches:
+      - 'release/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: True
+
+jobs:
+  compute-test-configs:
+    name: "Compute Configurations to Test"
+    if: >-
+      github.repository_owner == 'llvm' &&
+      github.event.action != 'closed'
+    runs-on: ubuntu-22.04
+    outputs:
+      projects: ${{ steps.vars.outputs.projects }}
+      check-targets: ${{ steps.vars.outputs.check-targets }}
+      test-build: ${{ steps.vars.outputs.check-targets != '' }}
+      test-platforms: ${{ steps.platforms.outputs.result }}
+    steps:
+      - name: Fetch LLVM sources
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 2
+
+      - name: Compute projects to test
+        id: vars
+        uses: ./.github/workflows/compute-projects-to-test
+
+      - name: Compute platforms to test
+        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea #v7.0.1
+        id: platforms
+        with:
+          script: |
+            linuxConfig = {
+              name: "linux-x86_64",
+              runs_on: "ubuntu-22.04"
+            }
+            windowsConfig = {
+              name: "windows-x86_64",
+              runs_on: "windows-2022"
+            }
+            macConfig = {
+              name: "macos-x86_64",
+              runs_on: "macos-13"
+            }
+            macArmConfig = {
+              name: "macos-aarch64",
+              runs_on: "macos-14"
+            }
+
+            configs = []
+
+            const base_ref = process.env.GITHUB_BASE_REF;
+            if (base_ref.startsWith('release/')) {
+              // This is a pull request against a release branch.
+              configs.push(macConfig)
+              configs.push(macArmConfig)
+            }
+
+            return configs;
+
+  ci-build-test:
+    # If this job name is changed, then we need to update the job-name
+    # paramater for the timeout-save step below.
+    name: "Build"
+    needs:
+      - compute-test-configs
+    permissions:
+      actions: write #pr-sccache-save may delete artifacts.
+    runs-on: ${{ matrix.runs_on }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include: ${{ fromJson(needs.compute-test-configs.outputs.test-platforms) }}
+    if: needs.compute-test-configs.outputs.test-build == 'true'
+    steps:
+      - name: Fetch LLVM sources
+        uses: actions/checkout@v4
+
+      - name: Timeout Restore
+        id: timeout
+        uses: ./.github/workflows/timeout-restore
+        with:
+          artifact-name-suffix: ${{ matrix.name }}
+
+      - name: Setup Windows
+        uses: llvm/actions/setup-windows@main
+        if: ${{ runner.os == 'Windows' }}
+        with:
+          arch: amd64
+
+      - name: Install Ninja
+        uses: llvm/actions/install-ninja@main
+
+      - name: Setup sccache
+        uses: hendrikmuhs/ccache-action@v1
+        with:
+          max-size: 2G
+          variant: sccache
+          key: ci-${{ matrix.name }}
+
+      - name: Restore sccache from previous PR run
+        uses: ./.github/workflows/pr-sccache-restore
+        with:
+          artifact-name-suffix: ${{ matrix.name }}
+
+      - name: Configure
+        if: ${{ steps.timeout.outputs.exists != 'true' }}
+        shell: bash
+        run: |
+          cmake -B build -GNinja \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DLLVM_ENABLE_PROJECTS="${{ needs.compute-test-configs.outputs.projects }}" \
+            -DLLVM_ENABLE_ASSERTIONS=ON \
+            -DLLVM_LIT_ARGS="-v --no-progress-bar" \
+            -DCMAKE_C_COMPILER_LAUNCHER=sccache \
+            -DCMAKE_CXX_COMPILER_LAUNCHER=sccache \
+            -S llvm
+
+      - name: Build
+        shell: bash
+        timeout-minutes: 330
+        run: |
+          ninja -C build -k 0 ${{ needs.compute-test-configs.outputs.check-targets }}
+
+      - name: Timeout Save
+        if: always()
+        uses: ./.github/workflows/timeout-save
+        with:
+          job-name: "Build (${{ matrix.name }}, ${{ matrix.runs_on }})"
+          artifact-name-suffix: ${{ matrix.name }}
+          timeout-step: "Build"
+          timeout-minutes: 330
+
+      - name: Save sccache for next PR run
+        if: always()
+        uses: ./.github/workflows/pr-sccache-save
+        with:
+          artifact-name-suffix: ${{ matrix.name }}
diff --git a/.github/workflows/clang-tests.yml b/.github/workflows/clang-tests.yml
deleted file mode 100644
index 2569ce19518e3e..00000000000000
--- a/.github/workflows/clang-tests.yml
+++ /dev/null
@@ -1,38 +0,0 @@
-name: Clang Tests
-
-permissions:
-  contents: read
-
-on:
-  workflow_dispatch:
-  push:
-    branches:
-      - 'release/**'
-    paths:
-      - 'clang/**'
-      - '.github/workflows/clang-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!llvm/**'
-  pull_request:
-    branches:
-      - 'release/**'
-    paths:
-      - 'clang/**'
-      - '.github/workflows/clang-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!llvm/**'
-
-concurrency:
-  # Skip intermediate builds: always.
-  # Cancel intermediate builds: only if it is a pull request build.
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
-
-jobs:
-  check_clang:
-    if: github.repository_owner == 'llvm'
-    name: Test clang,lldb,libclc
-    uses: ./.github/workflows/llvm-project-tests.yml
-    with:
-      build_target: check-clang
-      projects: clang;lldb;libclc
diff --git a/.github/workflows/compute-projects-to-test/action.yml b/.github/workflows/compute-projects-to-test/action.yml
new file mode 100644
index 00000000000000..37df06c8c301c5
--- /dev/null
+++ b/.github/workflows/compute-projects-to-test/action.yml
@@ -0,0 +1,21 @@
+name: 'Compute Projects To Test'
+inputs:
+  projects:
+    required: false
+    type: 'string'
+
+outputs:
+  check-targets:
+    description: "A space delimited list of check-targets to pass to ninja."
+    value: ${{ steps.compute-projects.outputs.check-targets }}
+
+  projects:
+    description: "A semi-colon delimited list of projects to pass to -DLLVM_ENABLE_PROJECTS."
+    value: ${{ steps.compute-projects.outputs.projects }}
+
+runs:
+  using: "composite"
+  steps:
+    - id: compute-projects
+      run: .github/workflows/compute-projects-to-test/compute-projects-to-test.sh ${{ inputs.projects }}
+      shell: bash
diff --git a/.github/workflows/compute-projects-to-test/compute-projects-to-test.sh b/.github/workflows/compute-projects-to-test/compute-projects-to-test.sh
new file mode 100755
index 00000000000000..4cfbda0c82034c
--- /dev/null
+++ b/.github/workflows/compute-projects-to-test/compute-projects-to-test.sh
@@ -0,0 +1,221 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===----------------------------------------------------------------------===##
+
+#
+# This file generates a Buildkite pipeline that triggers the various CI jobs for
+# the LLVM project during pre-commit CI.
+#
+# See https://buildkite.com/docs/agent/v3/cli-pipeline#pipeline-format.
+#
+# As this outputs a yaml file, it's possible to log messages to stderr or
+# prefix with "#".
+
+
+set -eu
+set -o pipefail
+
+# Environment variables script works with:
+
+# Set by GitHub
+: ${GITHUB_OUTPUT:=}
+: ${RUNNER_OS:=}
+
+# Allow users to specify which projects to build.
+all_projects="bolt clang clang-tools-extra compiler-rt cross-project-tests flang libc libclc lld lldb llvm mlir openmp polly pstl"
+if [ "$#" -ne 0 ]; then
+  wanted_projects="${@}"
+else
+  wanted_projects="${all_projects}"
+fi
+
+# List of files affected by this commit
+: ${MODIFIED_FILES:=$(git diff --name-only HEAD~1...HEAD)}
+
+echo "Files modified:" >&2
+echo "$MODIFIED_FILES" >&2
+modified_dirs=$(echo "$MODIFIED_FILES" | cut -d'/' -f1 | sort -u)
+echo "Directories modified:" >&2
+echo "$modified_dirs" >&2
+echo "wanted_projects: $wanted_projects"
+
+function remove-unwanted-projects() {
+  projects=${@}
+  for project in ${projects}; do
+    if echo "$wanted_projects" | tr ' ' '\n' | grep -q -E "^${project}$"; then
+      echo "${project}"
+    fi
+  done
+}
+
+function compute-projects-to-test() {
+  projects=${@}
+  for project in ${projects}; do
+    echo "${project}"
+    case ${project} in
+    lld)
+      for p in bolt cross-project-tests; do
+        echo $p
+      done
+    ;;
+    llvm)
+      for p in bolt clang clang-tools-extra flang lld lldb mlir polly; do
+        echo $p
+      done
+    ;;
+    clang)
+      for p in clang-tools-extra compiler-rt flang libc lldb openmp cross-project-tests; do
+        echo $p
+      done
+    ;;
+    clang-tools-extra)
+      echo libc
+    ;;
+    mlir)
+      echo flang
+    ;;
+    *)
+      # Nothing to do
+    ;;
+    esac
+  done
+}
+
+function add-dependencies() {
+  projects=${@}
+  for project in ${projects}; do
+    echo "${project}"
+    case ${project} in
+    bolt)
+      for p in lld llvm; do
+        echo $p
+      done
+    ;;
+    cross-project-tests)
+      for p in lld clang; do
+        echo $p
+      done
+    ;;
+    clang-tools-extra)
+      for p in llvm clang; do
+        echo $p
+      done
+    ;;
+    compiler-rt|libc|openmp)
+      echo clang lld
+    ;;
+    flang|lldb)
+      for p in llvm clang; do
+        echo $p
+      done
+    ;;
+    lld|mlir|polly)
+      echo llvm
+    ;;
+    *)
+      # Nothing to do
+    ;;
+    esac
+  done
+}
+
+function exclude-linux() {
+  projects=${@}
+  for project in ${projects}; do
+    case ${project} in
+    cross-project-tests) ;; # tests failing
+    lldb)                ;; # tests failing
+    openmp)              ;; # https://github.com/google/llvm-premerge-checks/issues/410
+    *)
+      echo "${project}"
+    ;;
+    esac
+  done
+}
+
+function exclude-windows() {
+  projects=${@}
+  for project in ${projects}; do
+    case ${project} in
+    cross-project-tests) ;; # tests failing
+    compiler-rt)         ;; # tests taking too long
+    openmp)              ;; # TODO: having trouble with the Perl installation
+    libc)                ;; # no Windows support
+    lldb)                ;; # tests failing
+    bolt)                ;; # tests are not supported yet
+    *)
+      echo "${project}"
+    ;;
+    esac
+  done
+}
+
+# Prints only projects that are both present in $modified_dirs and the passed
+# list.
+function keep-modified-projects() {
+  projects=${@}
+  for project in ${projects}; do
+    if echo "$modified_dirs" | grep -q -E "^${project}$"; then
+      echo "${project}"
+    fi
+  done
+}
+
+function check-targets() {
+  projects=${@}
+  for project in ${projects}; do
+    case ${project} in
+    clang-tools-extra)
+      echo "check-clang-tools"
+    ;;
+    compiler-rt)
+      echo "check-all"
+    ;;
+    cross-project-tests)
+      echo "check-cross-project"
+    ;;
+    lldb)
+      echo "check-all" # TODO: check-lldb may not include all the LLDB tests?
+    ;;
+    pstl)
+      echo "check-all"
+    ;;
+    libclc)
+      echo "check-all"
+    ;;
+    *)
+      echo "check-${project}"
+    ;;
+    esac
+  done
+}
+
+# Generic pipeline for projects that have not defined custom steps.
+#
+# Individual projects should instead define the pre-commit CI tests that suits their
+# needs while letting them run on the infrastructure provided by LLVM.
+
+# Figure out which projects need to be built on each platform
+modified_projects="$(keep-modified-projects ${all_projects})"
+echo "modified_projects: $modified_projects"
+
+if [ "${RUNNER_OS}" = "Linux" ]; then
+  projects_to_test=$(exclude-linux $(compute-projects-to-test ${modified_projects}))
+elif [ "${RUNNER_OS}" = "Windows" ]; then
+  projects_to_test=$(exclude-windows $(compute-projects-to-test ${modified_projects}))
+else
+  echo "Unknown runner OS: $RUNNER_OS"
+  exit 1
+fi
+check_targets=$(check-targets $(remove-unwanted-projects ${projects_to_test}) | sort | uniq)
+projects=$(remove-unwanted-projects $(add-dependencies ${projects_to_test}) | sort | uniq)
+
+echo "check-targets=$(echo ${check_targets} | tr ' ' ' ')" >> $GITHUB_OUTPUT
+echo "projects=$(echo ${projects} | tr ' ' ';')" >> $GITHUB_OUTPUT
+
+cat $GITHUB_OUTPUT
diff --git a/.github/workflows/continue-timeout-job.yml b/.github/workflows/continue-timeout-job.yml
new file mode 100644
index 00000000000000..f3ff58c77cfe0e
--- /dev/null
+++ b/.github/workflows/continue-timeout-job.yml
@@ -0,0 +1,75 @@
+name: Continue Timeout Job
+
+on:
+  workflow_run:
+    workflows:
+      - "Windows Precommit Tests"
+      - "CI Tests"
+    types:
+      - completed
+
+permissions:
+  contents: read
+
+jobs:
+  restart:
+    name: "Restart Job"
+    permissions:
+      actions: write
+    runs-on: ubuntu-22.04
+    if: github.event.workflow_run.conclusion == 'failure'
+    steps:
+      - name: "Restart Job"
+        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea #v7.0.1
+        with:
+          script: |
+            const response = await github.rest.actions.listWorkflowRunArtifacts({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              run_id: context.payload.workflow_run.id
+            })
+
+            job_ids = [];
+
+            for (artifact of response.data.artifacts) {
+              console.log(artifact);
+              const match = artifact.name.match(/timeout-([0-9]+)/);
+              console.log(match);
+              if (!match) {
+                continue;
+              }
+              job_ids.push(match[1]);
+
+              // Delete the timeout artifact to prepare for the next run
+              await github.rest.actions.deleteArtifact({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                artifact_id: artifact.id
+              });
+            }
+
+            if (job_ids.length == 0) {
+              return;
+            }
+
+            if (job_ids.length > 1) {
+              // We aren't able to re-start multiple jobs individually, so our
+              // only option is to restart all failed jobs.
+              await github.rest.actions.reRunWorkflowFailedJobs({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                run_id: context.payload.workflow_run.id
+              })
+              console.log("Restarted workflow: " + context.payload.workflow_run.id);
+              return;
+            }
+
+            job_id = job_ids[0];
+            // This function does not exist even though it is in the document
+            //github.rest.actions.reRunJobForWorkflow({
+            await github.request('POST /repos/{owner}/{repo}/actions/jobs/{job_id}/rerun', {
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              job_id: job_id
+            })
+            console.log("Restarted job: " + job_id);
diff --git a/.github/workflows/get-job-id/action.yml b/.github/workflows/get-job-id/action.yml
new file mode 100644
index 00000000000000..65495efd86820a
--- /dev/null
+++ b/.github/workflows/get-job-id/action.yml
@@ -0,0 +1,30 @@
+name: Get Job ID
+inputs:
+  job-name:
+    required: false
+    type: 'string'
+
+outputs:
+  job-id:
+    description: "A space delimited list of check-targets to pass to ninja."
+    value: ${{ steps.job-id.outputs.result }}
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea #v7.0.1
+      id: job-id
+      with:
+        script: |
+          const job_data = await github.rest.actions.listJobsForWorkflowRun({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            run_id: context.runId,
+          });
+
+          for (job of job_data.data.jobs) {
+            console.log(job)
+            if (job.name == "${{ inputs.job-name }}") {
+              return job.id
+            }
+          }
diff --git a/.github/workflows/libclc-tests.yml b/.github/workflows/libclc-tests.yml
deleted file mode 100644
index 23192f776a985e..00000000000000
--- a/.github/workflows/libclc-tests.yml
+++ /dev/null
@@ -1,39 +0,0 @@
-name: libclc Tests
-
-permissions:
-  contents: read
-
-on:
-  workflow_dispatch:
-  push:
-    branches:
-      - 'release/**'
-    paths:
-      - 'libclc/**'
-      - '.github/workflows/libclc-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!clang/**'
-      - '!llvm/**'
-  pull_request:
-    branches:
-      - 'release/**'
-    paths:
-      - 'libclc/**'
-      - '.github/workflows/libclc-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!clang/**'
-      - '!llvm/**'
-
-concurrency:
-  # Skip intermediate builds: always.
-  # Cancel intermediate builds: only if it is a pull request build.
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
-
-jobs:
-  check_libclc:
-    if: github.repository_owner == 'llvm'
-    name: Test libclc
-    uses: ./.github/workflows/llvm-project-tests.yml
-    with:
-      projects: clang;libclc
diff --git a/.github/workflows/lld-tests.yml b/.github/workflows/lld-tests.yml
deleted file mode 100644
index 599c0975fa6858..00000000000000
--- a/.github/workflows/lld-tests.yml
+++ /dev/null
@@ -1,38 +0,0 @@
-name: LLD Tests
-
-permissions:
-  contents: read
-
-on:
-  workflow_dispatch:
-  push:
-    branches:
-      - 'release/**'
-    paths:
-      - 'lld/**'
-      - '.github/workflows/lld-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!llvm/**'
-  pull_request:
-    branches:
-      - 'release/**'
-    paths:
-      - 'lld/**'
-      - '.github/workflows/lld-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!llvm/**'
-
-concurrency:
-  # Skip intermediate builds: always.
-  # Cancel intermediate builds: only if it is a pull request build.
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
-
-jobs:
-  check_lld:
-    if: github.repository_owner == 'llvm'
-    name: Test lld
-    uses: ./.github/workflows/llvm-project-tests.yml
-    with:
-      build_target: check-lld
-      projects: lld
diff --git a/.github/workflows/lldb-tests.yml b/.github/workflows/lldb-tests.yml
deleted file mode 100644
index 6bb9721956258f..00000000000000
--- a/.github/workflows/lldb-tests.yml
+++ /dev/null
@@ -1,39 +0,0 @@
-name: lldb Tests
-
-permissions:
-  contents: read
-
-on:
-  workflow_dispatch:
-  push:
-    branches:
-      - 'release/**'
-    paths:
-      - 'lldb/**'
-      - '.github/workflows/lldb-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!clang/**'
-      - '!llvm/**'
-  pull_request:
-    branches:
-      - 'release/**'
-    paths:
-      - 'lldb/**'
-      - '.github/workflows/lldb-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
-      - '!clang/**'
-      - '!llvm/**'
-
-concurrency:
-  # Skip intermediate builds: always.
-  # Cancel intermediate builds: only if it is a pull request build.
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
-
-jobs:
-  build_lldb:
-    if: github.repository_owner == 'llvm'
-    name: Build lldb
-    uses: ./.github/workflows/llvm-project-tests.yml
-    with:
-      projects: clang;lldb
diff --git a/.github/workflows/llvm-tests.yml b/.github/workflows/llvm-tests.yml
index 64d60bc3da45e1..016da80472e20a 100644
--- a/.github/workflows/llvm-tests.yml
+++ b/.github/workflows/llvm-tests.yml
@@ -11,14 +11,12 @@ on:
     paths:
       - 'llvm/**'
       - '.github/workflows/llvm-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
   pull_request:
     branches:
       - 'release/**'
     paths:
       - 'llvm/**'
       - '.github/workflows/llvm-tests.yml'
-      - '.github/workflows/llvm-project-tests.yml'
 
 concurrency:
   # Skip intermediate builds: always.
@@ -27,14 +25,6 @@ concurrency:
   cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
 
 jobs:
-  check-all:
-    if: github.repository_owner == 'llvm'
-    name: Build and Test
-    uses: ./.github/workflows/llvm-project-tests.yml
-    with:
-      build_target: check-all
-      projects: clang;lld;libclc;lldb
-
   abi-dump-setup:
     if: github.repository_owner == 'llvm'
     runs-on: ubuntu-latest
diff --git a/.github/workflows/pr-sccache-restore/action.yml b/.github/workflows/pr-sccache-restore/action.yml
new file mode 100644
index 00000000000000..8aa87025ba54b7
--- /dev/null
+++ b/.github/workflows/pr-sccache-restore/action.yml
@@ -0,0 +1,26 @@
+name: PR sccache restore
+
+inputs:
+  artifact-name-suffix:
+    desciption: The suffix to append to the artifict name (sccache-pr#)
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - uses: ./.github/workflows/unprivileged-download-artifact
+      id: download-artifact
+      with:
+        artifact-name: sccache-pr${{ github.event.pull_request.number }}-${{ inputs.artifact-name-suffix }}
+
+    - shell: bash
+      if: steps.download-artifact.outputs.filename != ''
+      run: |
+        # Is this the best way to clear the cache?
+        rm -Rf .sccache/
+        unzip ${{ steps.download-artifact.outputs.filename }}
+        rm ${{ steps.download-artifact.outputs.filename }}
+        tar --zstd -xf sccache.tar.zst
+        rm sccache.tar.zst
+        ls -altr
+
diff --git a/.github/workflows/pr-sccache-save/action.yml b/.github/workflows/pr-sccache-save/action.yml
new file mode 100644
index 00000000000000..badf623d32d5ef
--- /dev/null
+++ b/.github/workflows/pr-sccache-save/action.yml
@@ -0,0 +1,27 @@
+name: PR sccache save
+inputs:
+  artifact-name-suffix:
+    desciption: The suffix to append to the artifict name (sccache-pr#)
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Package sccache Directory
+      shell: bash
+      run: |
+        # Dereference symlinks so that this works on Windows.
+        tar -h -c .sccache | zstd -T0 -c > sccache.tar.zst
+
+    - uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 #v4.3.0
+      with:
+        name: 'sccache-pr${{ github.event.number }}-${{ inputs.artifact-name-suffix }}'
+        path: sccache.tar.zst
+        retention-days: 7
+        overwrite: true
+
+    - shell: bash
+      run: |
+        rm sccache.tar.zst
+        sccache --show-stats
+
diff --git a/.github/workflows/timeout-restore/action.yml b/.github/workflows/timeout-restore/action.yml
new file mode 100644
index 00000000000000..417782ccc5ca18
--- /dev/null
+++ b/.github/workflows/timeout-restore/action.yml
@@ -0,0 +1,33 @@
+name: Timeout Restore
+description: Save build state from a timed out job.
+inputs:
+  artifact-name-suffix:
+    desciption: Suffix to add to the name of the artifact containing the build state.
+    required: true
+
+outputs:
+  exists:
+    description: "This is true if a previous timeout build was restored, false otherwise."
+    value: ${{ steps.timeout-artifact.exists }}
+
+runs:
+  using: "composite"
+  steps:
+    - name: Download Artifact
+      uses: actions/download-artifact@6b208ae046db98c579e8a3aa621ab581ff575935 # v4.1.1
+      with:
+        pattern: timeout-build-${{ inputs.artifact-name-suffix }}
+        merge-multiple: true
+
+    - name: Unpack Artifact
+      id: timeout-artifact
+      shell: bash
+      run: |
+        if [ -e llvm-project.tar.zst ]; then
+          tar --zstd -xf llvm-project.tar.zst
+          rm llvm-project.tar.zst
+          echo "exists=true" >> $GITHUB_OUTPUT
+        else
+          echo "exists=false" >> $GITHUB_OUTPUT
+        fi
+
diff --git a/.github/workflows/timeout-save/action.yml b/.github/workflows/timeout-save/action.yml
new file mode 100644
index 00000000000000..fcea59165cf30b
--- /dev/null
+++ b/.github/workflows/timeout-save/action.yml
@@ -0,0 +1,94 @@
+name: Timeout Save
+description: Save build state when a timeout occurs so that it can be reused when the job is restarted.
+inputs:
+  job-name:
+    description: The name of the job.  This is used to look up the job id.
+    required: true
+  artifact-name-suffix:
+    desciption: Suffix to add to the name of the artifact containing the build state.
+    required: true
+  timeout-step:
+    description: The step that we want to restart if there is a timeout.
+    required: true
+  timeout-minutes:
+    description: The value of timeout-minutes for this step.
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Check for timeout
+      uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea #v7.0.1
+      id: timeout
+      with:
+        script: |
+          const job_data = await github.rest.actions.listJobsForWorkflowRun({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            run_id: context.runId,
+          });
+
+          for (job of job_data.data.jobs) {
+            console.log(job)
+            if (job.name != "${{ inputs.job-name }}") {
+              continue;
+            }
+
+            for (step of job.steps) {
+              console.log(step);
+              if (step.name != "${{ inputs.timeout-step }}") {
+                continue;
+              }
+              if (step.conclusion != "failure") {
+                return false;
+              }
+
+              // This run failed, check for timeout.
+              console.log(step.completed_at)
+              console.log(step.started_at)
+              completed_at = Date.parse(step.completed_at);
+              started_at = Date.parse(step.started_at);
+              console.log(completed_at)
+              console.log(started_at)
+              const diff = (completed_at - started_at) / 1000;
+              console.log(diff);
+              if (diff > 60 * ${{ inputs.timeout-minutes }})
+                return true;
+            }
+          }
+          return false;
+
+    - name: Save Working Directory
+      shell: bash
+      if: steps.timeout.outputs.result == 'true'
+      run: |
+        # Dereference symlinks so that this works on Windows.
+        tar -h -c . | zstd -T0 -c > ../llvm-project.tar.zst
+        mv ../llvm-project.tar.zst .
+
+    - name: Upload Working Directory
+      uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 #v4.3.0
+      if: steps.timeout.outputs.result == 'true'
+      with:
+        name: timeout-build-${{ inputs.artifact-name-suffix }}
+        path: llvm-project.tar.zst
+        retention-days: 2
+
+    - name: Get Job ID
+      id: job-id
+      if: steps.timeout.outputs.result == 'true'
+      uses: ./.github/workflows/get-job-id
+      with:
+        job-name: ${{ inputs.job-name }}
+
+    - name: Create Timeout File
+      if: steps.timeout.outputs.result == 'true'
+      shell: bash
+      run: touch timeout-${{ steps.job-id.outputs.job-id }}
+
+    - name: Upload Timeout File
+      if: steps.timeout.outputs.result == 'true'
+      uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 #v4.3.0
+      with:
+        name: timeout-${{ steps.job-id.outputs.job-id }}
+        path: timeout-${{ steps.job-id.outputs.job-id }}
diff --git a/.github/workflows/unprivileged-download-artifact/action.yml b/.github/workflows/unprivileged-download-artifact/action.yml
new file mode 100644
index 00000000000000..5ff657d9378895
--- /dev/null
+++ b/.github/workflows/unprivileged-download-artifact/action.yml
@@ -0,0 +1,77 @@
+name: Unprivileged Download Artifact
+description: Download artifacts from another workflow run without using an access token.
+inputs:
+  run-id:
+    description: The run-id for the workflow run that you want to download the artifact from.  If ommited it will download the most recently created artifact from the repo with the artifact-name.
+    required: false
+  artifact-name:
+    desciption: The name of the artifact to download.
+    required: true
+
+
+outputs:
+  filename:
+    description: "The filename of the downloaded artifact or the empty string if the artifact was not found."
+    value: ${{ steps.download-artifact.outputs.filename }}
+  artifact-id:
+    description: "The id of the artifact being downloaded."
+    value: ${{ steps.artifact-url.outputs.id }}
+
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea #v7.0.1
+      id: artifact-url
+      with:
+        script: |
+          var response;
+          if (!"${{ inputs.run-id }}") {
+            response = await github.rest.actions.listArtifactsForRepo({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              name: "${{ inputs.artifact-name }}"
+            })
+          } else {
+            const response = await github.rest.actions.listWorkflowRunArtifacts({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              run_id: "${{ inputs.run-id }}",
+              name: "${{ inputs.artifact-name }}"
+            })
+          }
+
+          console.log(response)
+
+          for (artifact of response.data.artifacts) {
+            console.log(artifact);
+          }
+
+          if (response.data.artifacts.length == 0) {
+            console.log("Could not find artifact ${{ inputs.artifact-name }} for workflow run ${{ inputs.run-id }}")
+            return;
+          }
+
+          const url_response = await github.rest.actions.downloadArtifact({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            artifact_id: response.data.artifacts[0].id,
+            archive_format: "zip"
+          })
+
+          core.setOutput("url", url_response.url);
+          core.setOutput("id", response.data.artifacts[0].id);
+
+    - shell: bash
+      run: |
+        echo "${{ steps.artifact-url.outputs.url }}"
+        echo "${{ steps.artifact-url.outputs.result }}"
+        echo "${{ steps.artifact-url.outputs.result.url }}"
+        echo "${{ steps.artifact-url.outputs.result.id }}"
+
+    - shell: bash
+      if: steps.artifact-url.outputs.url != ''
+      id: download-artifact
+      run: |
+        curl -L -o ${{ inputs.artifact-name }}.zip "${{ steps.artifact-url.outputs.url }}"
+        echo "filename=${{ inputs.artifact-name }}.zip" >> $GITHUB_OUTPUT
diff --git a/llvm/a b/llvm/a
new file mode 100644
index 00000000000000..e69de29bb2d1d6