On x86 C1 emits two relocations for polls

From Tom Rodriguez:

If you run with -XX:+PrintRelocations you’ll see output kind of like this:

relocInfo@0x0000000107d7b50e [type=10(poll) addr=0x0000000107d7b6ab offset=113]
        @0x0000000107d7b510: a400
relocInfo@0x0000000107d7b510 [type=10(poll) addr=0x0000000107d7b6ab offset=0 format=1]
        @0x0000000107d7b512: b423

The reason is that the shared add_debug_info_for branch calls relocate but so does the testl code for the poll itself. It’s not a big deal, though I think it may be what causes this fixup of the operand type in fix_relocation_after_move in relocInfo_x86.cpp:

#ifdef _LP64
 if (!Assembler::is_polling_page_far()) {
   typedef Assembler::WhichOperand WhichOperand;
   WhichOperand which = (WhichOperand) format();
   // This format is imm but it is really disp32
   which = Assembler::disp32_operand;

The shared reloc has the wrong format so it has to be fixed up.

The extra relocate call is benign I think exception that it’s used in emit_opBranch:

 if (op->cond() == lir_cond_always) {
   if (op->info() != NULL) add_debug_info_for_branch(op->info());
   __ jmp (*(op->label()));

I don’t know what’s going on here but I assume this should really be a safe point poll. Simply adding debug info doesn’t really do anything.