[llvm][clang] Allocate a new stack instead of spawning a new thread to get more stack space (#133173)

Clang spawns a new thread to avoid running out of stack space. This can
make debugging and performance analysis more difficult as how the
threads are connected is difficult to recover.

This patch introduces `runOnNewStack` and applies it in Clang. On
platforms that have good support for it this allocates a new stack and
moves to it using assembly. Doing split stacks like this actually runs
on most platforms, but many debuggers and unwinders reject the large or
backwards stack offsets that occur. Apple platforms and tools are known
to support this, so this only enables it there for now.

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 243e0a3..5fe80fc 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1265,7 +1265,7 @@ bool CompilerInstance::compileModule(SourceLocation ImportLoc,
 
   // Execute the action to actually build the module in-place. Use a separate
   // thread so that we get a stack large enough.
-  bool Crashed = !llvm::CrashRecoveryContext().RunSafelyOnThread(
+  bool Crashed = !llvm::CrashRecoveryContext().RunSafelyOnNewStack(
       [&]() {
         GenerateModuleFromModuleMapAction Action;
         Instance.ExecuteAction(Action);