[cheri_init_globals.h] Avoid using cgetaddr/cgetoffset in assembly

The upcoming standard no longer includes cgetoffset (and cgetaddr has
been removed in ISAv9). For now the assembly code still accepts cgetaddr
and converts it to a move, but use an intrinsic call instead as that can
be optimized to a subregister read on next use rather the requiring an
explicit move.

Author: arichardson

clang/lib/Headers/cheri_init_globals.h

@@ -76,13 +76,13 @@ __attribute__((weak)) extern void *__capability __cap_table_end;
  * position-dependent executables.
  */
 #ifdef CHERI_INIT_GLOBALS_USE_OFFSET
-#define cgetaddr_or_offset "cgetoffset"
 #define csetaddr_or_offset "csetoffset"
+#define cheri_address_or_offset_get(_cap) __builtin_cheri_offset_get((_cap))
 #define cheri_address_or_offset_set(_cap, _val)                                \
   __builtin_cheri_offset_set((_cap), (_val))
 #else
-#define cgetaddr_or_offset "cgetaddr"
 #define csetaddr_or_offset "csetaddr"
+#define cheri_address_or_offset_get(_cap) __builtin_cheri_address_get((_cap))
 #define cheri_address_or_offset_set(_cap, _val)                                \
   __builtin_cheri_address_set((_cap), (_val))
 #endif
@@ -219,13 +219,11 @@ cheri_init_globals_3(void *__capability data_cap,
           "lla %1, __stop___cap_relocs\n\t"
           : "=r"(start_addr), "=r"(stop_addr));
 #else
-  void *__capability tmp;
-  __asm__ (
-       "cllc %2, __start___cap_relocs\n\t"
-       cgetaddr_or_offset " %0, %2\n\t"
-       "cllc %2, __stop___cap_relocs\n\t"
-       cgetaddr_or_offset " %1, %2\n\t"
-       :"=r"(start_addr), "=r"(stop_addr), "=&C"(tmp));
+  __asm__("cllc %0, __start___cap_relocs\n\t"
+          "cllc %1, __stop___cap_relocs\n\t"
+          : "=C"(start_relocs), "=C"(stop_relocs));
+  start_addr = cheri_address_or_offset_get(start_relocs);
+  stop_addr = cheri_address_or_offset_get(stop_relocs);
 #endif
 #else
 #error Unknown architecture