Compiler optimization of division and remainder

On another newsgroup, a poster claimed that some compilers could
optimize a program which used both a/b and a%b (both quotient and
remainder with the _same_ arguments) in such a way that the compiler
would perform only a single hardware division operation and arrange to
use both the quotient and remainder from this single operation.


I've looked at a lot of highly optimized code from a lot of compilers,
and I can't recall ever seeing such an optimization.


I can imagine how such an optimization would be done, but I can't
imagine many other places -- except for possibly keeping track of a
shifted out carry bit in a shift operation, or gathering both the high
order and low order bits of a double-precision integer multiplication
-- where such an optimization would be used. Due to the relatively
low frequency (statically) of occurrence of such a situation, I can
imagine that such an optimization never 'makes the cut'. (I would
also imagine that the general case would easily be NP-complete, as are
most code generation optimizations.)


I have seen references to some pretty garish shifting hacks in the GNU
C compiler, but I'm not sure how many other compilers dabble in this
sort of thing.


I would be interested in a) references to real, existing compilers
which are capable of doing such a thing; and b)
papers/tech-reports/theses, etc. which say how to do this.


Thx in advance.
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