[PATCH] D155731: [AIX] Define llvm::thread::DefaultStackSize to 4 megabytes on AIX

[wael yehia via Phabricator via llvm-commits]

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Link time thinLTO spawns pthreads to parallelize optimization and codegen of the input bitcode files.
On AIX, the pthread's stack size limit is ~192k for 64-bit programs.
If `std::optional<unsigned> llvm::thread::DefaultStackSize` is initialized, then its value is used on a call to <https://github.com/llvm/llvm-project/blob/main/llvm/lib/Support/Unix/Threading.inc#L78> `pthread_attr_setstacksize` before `pthread_create` occurs.

We think increasing the default thread stack size limit in llvm on AIX to 4mb make sense.


https://reviews.llvm.org/D155731

Files:
  llvm/lib/Support/Threading.cpp


Index: llvm/lib/Support/Threading.cpp
===================================================================
--- llvm/lib/Support/Threading.cpp
+++ llvm/lib/Support/Threading.cpp
@@ -83,6 +83,8 @@
   // the same interface as std::thread but requests the same stack size as the
   // main thread (8MB) before creation.
 const std::optional<unsigned> llvm::thread::DefaultStackSize = 8 * 1024 * 1024;
+#elif defined(_AIX)
+const std::optional<unsigned> llvm::thread::DefaultStackSize = 4 * 1024 * 1024;
 #else
 const std::optional<unsigned> llvm::thread::DefaultStackSize;
 #endif


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