[LibOS] Remove IN_SHIM macro in shim_tls.h

LibOS/shim/include/shim_tls.h

@@ -1,21 +1,8 @@
 #ifndef _SHIM_TLS_H_
 #define _SHIM_TLS_H_
 
-#ifdef IN_SHIM
-
 #include <atomic.h>
 
-#else  /* !IN_SHIM */
-/* workaround to make glibc build
- * the following structure must match to the one defined in pal/lib/atomic.h
- */
-#ifdef __x86_64__
-struct atomic_int {
-    volatile int64_t counter;
-};
-#endif
-#endif /* IN_SHIM */
-
 #define SHIM_TLS_CANARY 0xdeadbeef
 
 struct shim_regs {
@@ -68,14 +55,11 @@ struct shim_tcb {
     } test_range;
 };
 
-#ifdef IN_SHIM
-
-#include <stddef.h>
-
 void init_tcb (shim_tcb_t * tcb);
 
 static inline shim_tcb_t * shim_get_tcb(void)
 {
+    /* TODO: optimize to use single movq %gs:<offset> */
     PAL_TCB * tcb = pal_get_tcb();
     return (shim_tcb_t*)tcb->libos_tcb;
 }
@@ -87,6 +71,4 @@ static inline bool shim_tls_check_canary(void)
     return shim_tcb->canary == SHIM_TLS_CANARY;
 }
 
-#endif /* IN_SHIM */
-
 #endif /* _SHIM_H_ */