Re: Use of unaligned load/stores by compilers

corbett@lupa.Eng.Sun.COM (Robert Corbett) wrote:


>>Fortran lets you use equivalence statements to misalign double precision
>>floats, other than that I don't know of any languages where misaligned
>>data will happen without extraordinary programmer effort. -John]
>
>There are a few languages that allow users to specify that data is
>unaligned. COBOL, PL/I and Ada come to mind.


The Pascal "packed" data was always a potential alignment problem. I
haven't used Pascal in ages but I recall that the semantics of
"packed" being implementation-defined but was never used for anything
other than character data.


Scott Amspoker
scott@basis.com
http://www.rt66.com/sda
[I believe that packed reflected a peculiarity of the CDC6600 on which
Pascal was initially implemented. The machine was word oriented, and
there were instructions that packed and unpacked characters into words,
so the only thing that ever happened to packed data was that it got
unpacked before subsequent processing -John]


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