tsan: introduce kAccessExternalPC

[dvyukov]

Summary

Add kAccessExternal memory access flag that denotes
memory accesses with PCs that may have kExternalPCBit set.
In preparation for MemoryAccess refactoring.
Currently unused, but will allow to skip a branch.

Depends on D107464.

compiler-rt/lib/tsan/rtl/tsan_interface.inc

void __tsan_write4(void *addr) {
   MemoryAccess(cur_thread(), CALLERPC, (uptr)addr, 4, kAccessWrite);
 }
 
 void __tsan_write8(void *addr) {
   MemoryAccess(cur_thread(), CALLERPC, (uptr)addr, 8, kAccessWrite);
 }
 
 void __tsan_read1_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 1, kAccessRead);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 1, kAccessRead | kAccessExternalPC);
 }
 
 void __tsan_read2_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 2, kAccessRead);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 2, kAccessRead | kAccessExternalPC);
 }
 
 void __tsan_read4_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 4, kAccessRead);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 4, kAccessRead | kAccessExternalPC);
 }
 
 void __tsan_read8_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 8, kAccessRead);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 8, kAccessRead | kAccessExternalPC);
 }
 
 void __tsan_write1_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 1, kAccessWrite);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 1, kAccessWrite | kAccessExternalPC);
 }
 
 void __tsan_write2_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 2, kAccessWrite);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 2, kAccessWrite | kAccessExternalPC);
 }
 
 void __tsan_write4_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 4, kAccessWrite);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 4, kAccessWrite | kAccessExternalPC);
 }
 
 void __tsan_write8_pc(void *addr, void *pc) {
-  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 8, kAccessWrite);
+  MemoryAccess(cur_thread(), STRIP_PAC_PC(pc), (uptr)addr, 8, kAccessWrite | kAccessExternalPC);
 }
 
 ALWAYS_INLINE USED void __tsan_unaligned_read2(const void *addr) {
   UnalignedMemoryAccess(cur_thread(), CALLERPC, (uptr)addr, 2, kAccessRead);
 }
 
 ALWAYS_INLINE USED void __tsan_unaligned_read4(const void *addr) {
   UnalignedMemoryAccess(cur_thread(), CALLERPC, (uptr)addr, 4, kAccessRead);

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

 typedef uptr AccessType;
 
 enum : AccessType {
   kAccessWrite = 0,
   kAccessRead = 1 << 0,
   kAccessAtomic = 1 << 1,
   kAccessVptr = 1 << 2,  // read or write of an object virtual table pointer
   kAccessFree = 1 << 3,  // synthetic memory access during memory freeing
+  kAccessExternalPC = 1 << 4,  // access PC can have kExternalPCBit set
 };
 
 void MemoryAccess(ThreadState *thr, uptr pc, uptr addr,
     int kAccessSizeLog, bool kAccessIsWrite, bool kIsAtomic);
 void MemoryAccessImpl(ThreadState *thr, uptr addr,
     int kAccessSizeLog, bool kAccessIsWrite, bool kIsAtomic,
     u64 *shadow_mem, Shadow cur);
 void MemoryAccessRange(ThreadState *thr, uptr pc, uptr addr,