[llvm] [AIX][PowerPC] Teach the Threading Library About the Number of Physical Cores on AIX (PR #67683)

[via llvm-commits]

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@@ -432,6 +436,8 @@ static int computeHostNumPhysicalCores() {
       static_cast<uintptr_t>(reinterpret_cast<unsigned int &>(CVT[CVTCSD])));
   return reinterpret_cast<int &>(CSD[CSD_NUMBER_ONLINE_STANDARD_CPS]);
 }
+#elif defined(_AIX)
+static int computeHostNumPhysicalCores() { return _system_configuration.ncpus; }
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xingxue-ibm wrote:

```suggestion
static int computeHostNumPhysicalCores() { return sysconf(_SC_NPROCESSORS_ONLN); }
```

https://github.com/llvm/llvm-project/pull/67683