PR20989, sparc GOT sequence optimization

[Jose E. Marchesi]

    >     +/* Return whether H is local and its ADDRESS is within 4G of
    >     +   _GLOBAL_OFFSET_TABLE_ and thus the offset may be calculated by a
    >     +   sethi, xor sequence.  */
    > 
    > Generally speaking the address must be within {+-}2G of
    > _GLOBAL_OFFSET_TABLE_, i.e. there can be negative offsets.
    
    I allowed +/-4G, and believe that is the range of sethi, xor.
    
    	sethi	%hi(-1), %l7      # 0x0000 0000 ffff fc00
    	xor	%l7, -0x400, %l6  # 0xffff ffff 0000 0000
    
    	xor	%l7, 0x3ff, %l5   # 0x0000 0000 ffff ffff

I stand corrected.  In 64-bits the range is indeed a signed 33-bit
constant.