The adrp() (address of page) assembler macro can reach anywhere in the 48-bit AArch64 address space. However, byte_map_base is not necessarily an address: it might even wrap around the address space so that it is a negative 64-bit constant. In that case, we should not use ADRP to form its address.

While investigating this bug we discovered that the code stubs for C1's G1 pre- and post-barriers push the incorrect set of registers. We must include the call-clobbered vector registers too; they probably won't be used by the native runtime, but the ABI says that they may be so we must save them.