[ASan] Update meminstrinsics to use library memmove rather than internal (llvm#160740)

Currently `memcpy` and `memset` intrinsics map through to the library implementations if ASan has been inited, whereas `memmove` always calls `internal_memmove`. This patch changes `memmove` to use the library implementation if ASan has been inited.

Author: DanBlackwell

compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp

@@ -55,8 +55,10 @@ using namespace __asan;
  if (LIKELY(replace_intrin_cached)) { \
  ASAN_READ_RANGE(ctx, from, size); \
  ASAN_WRITE_RANGE(ctx, to, size); \
+ } else if (UNLIKELY(!AsanInited())) { \
+ return internal_memmove(to, from, size); \
  } \
- return internal_memmove(to, from, size); \
+ return REAL(memmove)(to, from, size);  \
  } while (0)
 
 void *__asan_memcpy(void *to, const void *from, uptr size) {

compiler-rt/lib/asan/asan_interceptors_memintrinsics.h

@@ -20,6 +20,7 @@
 
 DECLARE_REAL(void *, memcpy, void *to, const void *from, SIZE_T size)
 DECLARE_REAL(void *, memset, void *block, int c, SIZE_T size)
+DECLARE_REAL(void *, memmove, void *to, const void *from, SIZE_T size)
 
 namespace __asan {