[libcxx-commits] [libcxx] [llvm] [libc++] Automatically detect the OS in benchmark jobs (PR #224386)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne created https://github.com/llvm/llvm-project/pull/224386

This simplifies the machines.json definition: we don't have to explicitly say what OS we're running on, the job just figures it out.

>From d6224e87c8396194fa1cf9ceb6b6dbf0c6119e81 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Thu, 17 Sep 2026 12:15:33 -0700
Subject: [PATCH] [libc++] Automatically detect the OS in benchmark jobs

This simplifies the machines.json definition: we don't have to explicitly
say what OS we're running on, the job just figures it out.
---
 .github/workflows/libcxx-benchmark-commit.yml | 6 +++---
 .github/workflows/libcxx-pr-benchmark.yml     | 6 +++---
 libcxx/utils/ci/lnt/machines.json             | 3 ---
 3 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/.github/workflows/libcxx-benchmark-commit.yml b/.github/workflows/libcxx-benchmark-commit.yml
index 06f82383437a9..040c0a7536dc4 100644
--- a/.github/workflows/libcxx-benchmark-commit.yml
+++ b/.github/workflows/libcxx-benchmark-commit.yml
@@ -117,17 +117,17 @@ jobs:
           fetch-tags: true
 
       - name: Install Python
-        if: ${{ matrix.running-on == 'linux' }} # installed via Homebrew on macOS
+        if: runner.os == 'Linux' # installed via Homebrew on macOS
         uses: actions/setup-python at ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
         with:
           python-version: '3.14'
 
       - name: Select Xcode
-        if: ${{ matrix.running-on == 'macos' }}
+        if: runner.os == 'macOS'
         run: echo "DEVELOPER_DIR=/Applications/Xcode_${{ matrix.xcode-version }}.app/Contents/Developer" >> $GITHUB_ENV
 
       - name: Install dependencies via Homebrew
-        if: ${{ matrix.running-on == 'macos' }}
+        if: runner.os == 'macOS'
         run: |
           brew update
           brew install ninja cmake python at 3.14
diff --git a/.github/workflows/libcxx-pr-benchmark.yml b/.github/workflows/libcxx-pr-benchmark.yml
index bad08ce8afa72..52d3ec6cedd6b 100644
--- a/.github/workflows/libcxx-pr-benchmark.yml
+++ b/.github/workflows/libcxx-pr-benchmark.yml
@@ -124,17 +124,17 @@ jobs:
           fetch-tags: true # This job requires access to all the Git branches so it can diff against (usually) main
 
       - name: Install Python
-        if: ${{ matrix.running-on == 'linux' }} # installed via Homebrew on macOS
+        if: runner.os == 'Linux' # installed via Homebrew on macOS
         uses: actions/setup-python at ece7cb06caefa5fff74198d8649806c4678c61a1 # v6.3.0
         with:
           python-version: '3.14'
 
       - name: Select Xcode
-        if: ${{ matrix.running-on == 'macos' }}
+        if: runner.os == 'macOS'
         run: echo "DEVELOPER_DIR=/Applications/Xcode_${{ matrix.xcode-version }}.app/Contents/Developer" >> $GITHUB_ENV
 
       - name: Install dependencies via Homebrew
-        if: ${{ matrix.running-on == 'macos' }}
+        if: runner.os == 'macOS'
         run: |
           brew update
           brew install ninja cmake python at 3.14
diff --git a/libcxx/utils/ci/lnt/machines.json b/libcxx/utils/ci/lnt/machines.json
index 98708cbf9d731..ca55a7fc3c241 100644
--- a/libcxx/utils/ci/lnt/machines.json
+++ b/libcxx/utils/ci/lnt/machines.json
@@ -3,7 +3,6 @@
     "lnt-machine": "macos-26.5-arm64-20260812",
     "runner": ["self-hosted", "macOS", "26.5", "ARM64", "apple-runners"],
     "cxx": "clang++",
-    "running-on": "macos",
     "xcode-version": "26.5",
     "benchmark-suite-version": "8bb5e216937e6b541f351aa1637c67e85a43ada0",
     "cmake-cache": "libcxx/utils/ci/lnt/cmake/generic.cmake",
@@ -19,7 +18,6 @@
     "lnt-machine": "macos-26.5-arm64-hardenedfast-20260821",
     "runner": ["self-hosted", "macOS", "26.5", "ARM64", "apple-runners"],
     "cxx": "clang++",
-    "running-on": "macos",
     "xcode-version": "26.5",
     "benchmark-suite-version": "8bb5e216937e6b541f351aa1637c67e85a43ada0",
     "cmake-cache": "libcxx/utils/ci/lnt/cmake/hardened-fast.cmake",
@@ -35,7 +33,6 @@
     "lnt-machine": "linux-x86_64-20260812",
     "runner": "llvm-premerge-libcxx-runners",
     "cxx": "clang++-22",
-    "running-on": "linux",
     "benchmark-suite-version": "8bb5e216937e6b541f351aa1637c67e85a43ada0",
     "cmake-cache": "libcxx/utils/ci/lnt/cmake/generic.cmake",
     "coverage": {