Re: How does GCC access global variables on x86

[Andrew Haley <aph at redhat dot com>]

On 02/07/2012 04:56 PM, Xin Tong wrote:
> I am wondering how gcc accesses global variables on x86. from the code
> i have seen so far, it seems to use the %RIP as the base register. Is
> it always like this?
> 
>   4006f9:       f0 80 0d bf 0b 20 00    lock orb $0x0,0x200bbf(%rip)
>      # 6012c0 <t2lockor>
>   400700:       00
> 
> t2lockor is a global variables.

This is x86_64, I think.  The answer is that it depends on whether you
are using PIC, and the model you're using.  Try -mcmodel=large for a
variation.  PC-relative loads are convenient for everything except the
large memory model.

Andrew.