[llvm] [benchmark] Sync a few commits from upstream to help with CPU count (PR #126410)

[Brad Smith via llvm-commits]

https://github.com/brad0 updated https://github.com/llvm/llvm-project/pull/126410

>From 3078c05364526dcbb7e9d293a34297e2e1c52cc0 Mon Sep 17 00:00:00 2001
From: Brad Smith <brad at comstyle.com>
Date: Sun, 9 Feb 2025 04:16:53 -0500
Subject: [PATCH] [benchmark] Sync a few commits from upstream to help with CPU
 count

Try to use the _SC_NPROCESSORS_ONLN sysconf elsewhere
(cherry picked from commit edb1e76d8cb080a396c7c992e5d4023e1a777bd1)

Replace usage of deprecated sysctl on macOS
(cherry picked from commit faaa266d33ff203e28b31dd31be9f90c29f28d04)

Retrieve the number of online CPUs on OpenBSD and NetBSD
(cherry picked from commit 41e81b1ca4bbb41d234f2d0f2c56591db78ebb83)

Update error message now that /proc/cpuinfo is no longer in use
(cherry picked from commit c35af58b61daa111c93924e0e7b65022871fadac)

Fix runtime crash when parsing /proc/cpuinfo fails
(cherry picked from commit 39be87d3004ff9ff4cdf736651af80c3d15e2497)
---
 third-party/benchmark/src/sysinfo.cc | 52 ++++++++++++++++------------
 1 file changed, 30 insertions(+), 22 deletions(-)

diff --git a/third-party/benchmark/src/sysinfo.cc b/third-party/benchmark/src/sysinfo.cc
index 8283a081ee80b4a..851f681c5a8a234 100644
--- a/third-party/benchmark/src/sysinfo.cc
+++ b/third-party/benchmark/src/sysinfo.cc
@@ -160,11 +160,11 @@ ValueUnion GetSysctlImp(std::string const& name) {
   int mib[2];
 
   mib[0] = CTL_HW;
-  if ((name == "hw.ncpu") || (name == "hw.cpuspeed")) {
+  if ((name == "hw.ncpuonline") || (name == "hw.cpuspeed")) {
     ValueUnion buff(sizeof(int));
 
-    if (name == "hw.ncpu") {
-      mib[1] = HW_NCPU;
+    if (name == "hw.ncpuonline") {
+      mib[1] = HW_NCPUONLINE;
     } else {
       mib[1] = HW_CPUSPEED;
     }
@@ -482,27 +482,14 @@ std::string GetSystemName() {
 }
 
 int GetNumCPUsImpl() {
-#ifdef BENCHMARK_HAS_SYSCTL
-  int num_cpu = -1;
-  if (GetSysctl("hw.ncpu", &num_cpu)) return num_cpu;
-  PrintErrorAndDie("Err: ", strerror(errno));
-#elif defined(BENCHMARK_OS_WINDOWS)
+#ifdef BENCHMARK_OS_WINDOWS
   SYSTEM_INFO sysinfo;
   // Use memset as opposed to = {} to avoid GCC missing initializer false
   // positives.
   std::memset(&sysinfo, 0, sizeof(SYSTEM_INFO));
   GetSystemInfo(&sysinfo);
-  return sysinfo.dwNumberOfProcessors;  // number of logical
-                                        // processors in the current
-                                        // group
-#elif defined(__linux__) || defined(BENCHMARK_OS_SOLARIS)
-  // Returns -1 in case of a failure.
-  int num_cpu = static_cast<int>(sysconf(_SC_NPROCESSORS_ONLN));
-  if (num_cpu < 0) {
-    PrintErrorAndDie("sysconf(_SC_NPROCESSORS_ONLN) failed with error: ",
-                     strerror(errno));
-  }
-  return num_cpu;
+  // number of logical processors in the current group
+  return static_cast<int>(sysinfo.dwNumberOfProcessors);
 #elif defined(BENCHMARK_OS_QNX)
   return static_cast<int>(_syspage_ptr->num_cpu);
 #elif defined(BENCHMARK_OS_QURT)
@@ -511,16 +498,37 @@ int GetNumCPUsImpl() {
     hardware_threads.max_hthreads = 1;
   }
   return hardware_threads.max_hthreads;
+#elif defined(BENCHMARK_HAS_SYSCTL)
+  int num_cpu = -1;
+  constexpr auto* hwncpu =
+#if defined BENCHMARK_OS_MACOSX
+      "hw.logicalcpu";
+#elif defined(HW_NCPUONLINE)
+      "hw.ncpuonline";
+#else
+      "hw.ncpu";
+#endif
+  if (GetSysctl(hwncpu, &num_cpu)) return num_cpu;
+  PrintErrorAndDie("Err: ", strerror(errno));
+#elif defined(_SC_NPROCESSORS_ONLN)
+  // Returns -1 in case of a failure.
+  int num_cpu = static_cast<int>(sysconf(_SC_NPROCESSORS_ONLN));
+  if (num_cpu < 0) {
+    PrintErrorAndDie("sysconf(_SC_NPROCESSORS_ONLN) failed with error: ",
+                     strerror(errno));
+  }
+  return num_cpu;
 #endif
   BENCHMARK_UNREACHABLE();
 }
 
 int GetNumCPUs() {
-  const int num_cpus = GetNumCPUsImpl();
+  int num_cpus = GetNumCPUsImpl();
   if (num_cpus < 1) {
     PrintErrorAndDie(
-        "Unable to extract number of CPUs.  If your platform uses "
-        "/proc/cpuinfo, custom support may need to be added.");
+        "Unable to extract number of CPUs.");
+    /* There is at least one CPU which we run on. */
+    num_cpus = 1;
   }
   return num_cpus;
 }