On Fri, 24 May 2024 14:49:05 GMT, Daniel Jeliński <djelin...@openjdk.org> wrote:
>> Just did the experiment and it turns out that `mov64(r15, >> (int64_t)small_jump_table)` and `lea(r15, >> ExternalAddress(small_jump_table))` produce exactly the same code: >> >> `0x00007fffe463d68b: 49 bf a0 d5 63 e4 ff 7f 00 00 movabs >> r15,0x7fffe463d5a0` >> >> The code in `MacroAssembler` for `lea` calls `mov_literal64` with no check >> for whether it can be ip-relative. >> >> I tried doing it myself via `leaq(r15, Address(rip, >> (int64_t)small_jump_table - (int64_t)(__ pc())))` but there is no definition >> in `register_x86.hpp` for register `rip`. So I'm not sure exactly how to >> produce RIP-relative addressing. > > Thanks for checking. Well I know that the `MacroAssembler::movdqu(XMMRegister > dst, AddressLiteral src, Register rscratch)` method actually generates > rip-relative addresses. Maybe we could copy some of that code. Use `lea` and `InternalAddress()` for referencing jump tables since the addresses are in the same code section. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1613648648
