LO_SUM memrefs offsettable ?

Michael Hayes m.hayes@elec.canterbury.ac.nz
Mon Jan 25 00:11:00 GMT 1999


Jeffrey A Law writes:
 > I think we compute the address as:
 > 
 > (high (plus (symbol_ref) (rounded_constant))
 > (lo_sum (tmpreg) (plus (symbol_ref) (constant))

Ah, I overlooked the possibility of rounding the high part of the
address.  That's a good idea.  Does the sparc does this as well?  If
not, it will be harder to describe.  I was hoping to describe the
HIGH/LO_SUM behaviour with two parameters which could be used to
determine the maximum offset.

 > I believe the maximum offset for the PA is +-8K.

This makes sense.  If the sparc used similar rounding for the HIGH
part, I imagine the maximum offset would be +-4K.

Actually, I would have thought that the maximum offset we could use
would be a bit less due to quantization of the HIGH part.

Michael.







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