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Re: patch to canonize unsigned tree-csts



I was thinking that we should always be able to use the constant as-is
for max_wide_int-based and addr_wide_int-based operations.  The small_prec
again, you can get edge cased to death here.    i think it would work
for max because that really is bigger than anything else, but it is
possible (though unlikely) to have something big converted to an address
by truncation.
But I'd have expected that conversion to be represented by an explicit
CONVERT_EXPR or NOP_EXPR.  It seems wrong to use addr_wide_int directly on
something that isn't bit- or byte-address-sized.  It'd be the C equivalent
of int + long -> int rather than the expected int + long -> long.

Same goes for wide_int.  If we're doing arithmetic at a specific
precision, it seems odd for one of the inputs to be wider and yet
not have an explicit truncation.
you miss the second reason why we needed addr-wide-int. A large amount of the places where the addressing arithmetic is done are not "type safe". Only the gimple and rtl that is translated from the source code is really type safe. In passes like the strength reduction where they just "grab things from all over", the addr-wide-int or the max-wide-int are safe haven structures that are guaranteed to be large enough to not matter. So what i fear here is something like a very wide loop counter being grabbed into some address calculation.

Thanks,
Richard


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