Machine-independent intermediate languages

[David Keppel]

djones at goofy.megatest.UUCP (Dave Jones) writes:
>[ the HIIL compiler should(n't)... ]

Uh, great, now we have: HLL, HIIL, MIIL.  What's HIIL?

>[ global optimizations are machine-independent ]

I think that there are probably a *lot* of global optimizations that
*are* machine dependent.  Proof by authority: William Wulf said so.
Proof by trivialization: certain global variables may have their
concrete type assigned based on machine depndencies, and these in turn
will affect local computation; the concrete type assignment may in
some cases be available only after certain kinds of global
analysis[*].

Eventually you take a hit.

[*] Consider a language that supports two types of integers, a
    hardware-supported type and an arbitrary-precision type.  The
    variable may be declared with values outside the hardware type for
    some machines, inside the hardware type for other machines.  Even
    knowing whether the *declaration* fits may not be enough.  If the
    declaration doesn't fit the machine type and the *usage* is always
    within the machine type (which may be determined in at least some
    cases by looking at every assignment to the variable), then
    failure to do this (machine-dependent) global optimization will
    cause the compiler to allocate the arbitrary-preciesion type,
    which will generally be far less efficient.

	;-D on  ( Suboptimal reality )  Pardo
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