CISC to RISC translator? (Mikael Larsson)
Tue, 16 Aug 1994 08:14:51 GMT

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Newsgroups: comp.compilers
From: (Mikael Larsson)
Keywords: architecture, translator, question, comment
Organization: Erisoft AB, Sweden
Date: Tue, 16 Aug 1994 08:14:51 GMT

Hi netlanders,

It seems to me like the RISC CPU:s are finally going to replace
the 68k and 80x86 CPU:s also in the low cost (PC and Mac) segment.

To smoothen the transition, PC and Mac emulators have been developed.
These makes it possible to run PC and Mac native code on e.g. the
PowerMac. While there is often a sufficient processing capacity to
waste, it still appears to me like this approach is unnecessarily
wasteful. Speaking as a non-expert in this field (I┤m a hardware guy),
I would say that translation from native CISC code to native RISC code
would be quite feasible. The resulting RISC code would probably be
more efficient than emulated code, though not as efficient as full native code,
i.e. compiled from a high level language to native code. I have even heard
rumours about DEC making such a translator for converting VAX code to
Alpha code.

Could anyone explain to me why this isn┤t possible or where the main
difficulties are? Does anyone have any references to the work by DEC?
If it can be done, in what steps should it then preferrably be performed?
I┤ve heard of disassemblers. What is the output format of a disassembler?
Could the output of a disassembler be used as input for generating code
for another architecture? Does anyone know of any tools that could be used
to build a code translator?

Mikael Larsson
Erisoft, Luleň, Sweden
[The Vax to Alpha translator is real and apparently works quite well. An
important reason for that is that the Alpha uses the same data formats, so
you don't have to do byte swapping and the like. x86 emulators like Insignia's
are apparently compilers as well, compiling chunks on the fly. In many cases,
particularly DOS x86 systems, emulating the environment (devices, interrupts,
and the like) is harder than translating the actual code., -John]

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