tsan: introduce LazyInitialize

We call non-inlinable Initialize from all interceptors/syscalls,
but most of the time runtime is already initialized and this just
introduces unnecessary overhead.
Add LazyInitialize that (1) inlinable, (2) does nothing if
.preinit_array is enabled (expected case on Linux).

Depends on D107071.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D107072

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

@@ -249,7 +249,7 @@ static ThreadSignalContext *SigCtx(ThreadState *thr) {
 ScopedInterceptor::ScopedInterceptor(ThreadState *thr, const char *fname,
                                      uptr pc)
     : thr_(thr), in_ignored_lib_(false), ignoring_(false) {
-  Initialize(thr);
+  LazyInitialize(thr);
   if (!thr_->is_inited) return;
   if (!thr_->ignore_interceptors) FuncEntry(thr, pc);
   DPrintf("#%d: intercept %s()\n", thr_->tid, fname);
@@ -2488,10 +2488,7 @@ static __sanitizer_sighandler_ptr signal_impl(int sig,
 struct ScopedSyscall {
   ThreadState *thr;
 
-  explicit ScopedSyscall(ThreadState *thr)
-      : thr(thr) {
-    Initialize(thr);
-  }
+  explicit ScopedSyscall(ThreadState *thr) : thr(thr) { LazyInitialize(thr); }
 
   ~ScopedSyscall() {
     ProcessPendingSignals(thr);

compiler-rt/lib/tsan/rtl/tsan_rtl.cpp

@@ -384,9 +384,10 @@ void CheckUnwind() {
   PrintCurrentStackSlow(StackTrace::GetCurrentPc());
 }
 
+bool is_initialized;
+
 void Initialize(ThreadState *thr) {
   // Thread safe because done before all threads exist.
-  static bool is_initialized = false;
   if (is_initialized)
     return;
   is_initialized = true;

compiler-rt/lib/tsan/rtl/tsan_rtl.h

@@ -859,6 +859,19 @@ enum FiberSwitchFlags {
   FiberSwitchFlagNoSync = 1 << 0, // __tsan_switch_to_fiber_no_sync
 };
 
+extern bool is_initialized;
+
+ALWAYS_INLINE
+void LazyInitialize(ThreadState *thr) {
+  // If we can use .preinit_array, assume that __tsan_init
+  // called from .preinit_array initializes runtime before
+  // any instrumented code.
+#if !SANITIZER_CAN_USE_PREINIT_ARRAY
+  if (UNLIKELY(!is_initialized))
+    Initialize(thr);
+#endif
+}
+
 }  // namespace __tsan
 
 #endif  // TSAN_RTL_H