How to decide if a target supports relocations or not?

[HAO CHEN GUI]

Hi,

Some questions about relocation. Could anyone kindly help on them? 
Thanks a lot.

1 If targetm.asm_out.reloc_rw_mask () returns 0, does it mean the target 
doesn't support relocations in read only section. So it should be put in 
read-write section?

2 Here, does the read only section stand for rodata section or 
data.rel.ro section?

3 What's the relationships between PIC flag and relocations?

Thanks again.