quad aligned load/stores

[David Keaton]

>Will SUN handle non-quad alignments with hardware or software??

     The SPARC Architecture Manual, Version 9, says that "quadword
accesses shall be aligned on 16-byte boundaries" and unaligned
accesses cause a trap.  A given SPARC implementation is allowed, but
not required, to provide an exception to this rule and complete the
nonquadword-aligned access in hardware if it is word aligned.

     Therefore, the answer to the question should lie in the document
"Implementation Characteristics of Current SPARC-V9-based Products"
mentioned in the Architecture manual.  When I called SPARC
International a few days ago to get this document in reference to an
unrelated matter, they told me that the document did not exist because
nobody was building a SPARC-V9 implementation.  Therefore, V9 is a
vacuous standard, at least for now.

     Assuming it becomes nonvacuous some day, it would be interesting
to see whether a SPARC V9 ABI would require the stack to be quadword
aligned.  This could make a big difference in how many codes could
actually use quadwords efficiently.

					David Keaton
					dmkadmk.com