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Document existence of old (gencode) and new (igen) MIPS ISA simulators.

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Andrew Cagney 1998-01-16 01:09:15 +00:00
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sim/mips/README.Cygnus
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This directory contains two very different simulators:
o gencode (old)
Gencode.c outputs a single monolithic file that is
#included by interp.c
o igen (new)
The *.igen files are used as inputs to ../igen/igen.
A number of separate, fairly modula files, are created.
The new simulator has a number of advantages:
o builtin support for multi-simming (single simulator
image supporting a number of different instruction
set architectures).
o Easier maintenance. The input files are not confused
by an intermixing with the generator code.
gencode continues to exist so that old architectures can be emulated.
*.igen should be used when adding new architectures or adding
instructions to an existing ISA.
Known bugs?
A mips16 simulator cannot be built using igen. A custom mips16
engine.c needs to be written.
In mips.igen, the semantics for many of the instructions were created
using code generated by gencode. Those semantic segments could be
greatly simplified.
----
Old README.Cygnus ...
> README.Cygnus
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