[libc] inline thread self

[SchrodingerZhu]

The codegen for non-inlined version is "quite ugly" as it emits some checks to make sure the initialization routine is properly executed because the compiler does not see how the TLS object is initialized. This leads to some callq 0x0 junk in the final outputs.

For codegen details, see https://godbolt.org/z/rb5qYj3vY.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Schrodinger ZHU Yifan (SchrodingerZhu)

Changes

The codegen for non-inlined version is quite ugly. See https://godbolt.org/z/rb5qYj3vY

---

Full diff: https://github.com/llvm/llvm-project/pull/101739.diff

2 Files Affected:

• (modified) libc/src/__support/threads/thread.cpp (-3)
• (modified) libc/src/__support/threads/thread.h (+1-1)

diff --git a/libc/src/__support/threads/thread.cpp b/libc/src/__support/threads/thread.cpp
index 886281e0d50f7..dad4f75f092ed 100644
--- a/libc/src/__support/threads/thread.cpp
+++ b/libc/src/__support/threads/thread.cpp
@@ -17,9 +17,6 @@
 #include "src/__support/macros/attributes.h"
 
 namespace LIBC_NAMESPACE_DECL {
-
-LIBC_THREAD_LOCAL Thread self;
-
 namespace {
 
 using AtExitCallback = void(void *);
diff --git a/libc/src/__support/threads/thread.h b/libc/src/__support/threads/thread.h
index 68640cef32964..f2b1f6bbb253d 100644
--- a/libc/src/__support/threads/thread.h
+++ b/libc/src/__support/threads/thread.h
@@ -231,7 +231,7 @@ struct Thread {
   int get_name(cpp::StringStream &name) const;
 };
 
-extern LIBC_THREAD_LOCAL Thread self;
+LIBC_INLINE_VAR LIBC_THREAD_LOCAL Thread self;
 
 // Platforms should implement this function.
 [[noreturn]] void thread_exit(ThreadReturnValue retval, ThreadStyle style);