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.arch
Directive
Syntax
.arch
model
Description
The .arch
directive specifies the version of the Alpha architecture for which the
Assembler is to generate instructions. Regardless of the version actually
being used, any instruction in the entire instruction set is potentially
available through it. If the version does not support an instruction in its
hardware, then the compiler can produce a combination of instructions that
perform the same actions and that the version does support.
Note The
instructions that the assembler generates in this manner are usually
inefficient. However, if the instructions are generated for a particular
version of the Alpha architecture, then they will perform relatively well on
that architecture. On the other hand, they might perform very badly on
another architecture.
The valid values
for model, along with descriptions of the instructions that the
Assembler is to generate, are as follows:
|
Model |
Instructions to generate |
|
generic |
All
instructions that are hard-wired into every Alpha processor.
This is the
model that the Assembler assumes if you omit the .arch
directive. |
|
host |
All
instructions directly supported by the Alpha processor on which the
Assembler is running. |
|
ev4,ev5 |
All
instructions for the EV4 processor (21064, 20164A, 21066, and 21068
chips) and the EV5 processor (the 21164 chips that house the EV5
processor).
None of
these instructions requires emulation on any Alpha processor. |
|
ev56 |
All
instructions for the EV56 processor (the 21164 chips that house the
EV56 processor).
These are
the instructions supported by the EV4 processor, as well as the
instructions in the byte/word extension (BWX).
Applications
compiled with this model might incur emulation overhead on EV4 and EV5
processors. |
|
pca56 |
All
instructions for the PCA56 processor (21164PC chips).
These are
the instructions supported by the EV4 processor, as well as the
instructions in the byte/word extension (BWX) and the multimedia
extension (MAX).
Applications
compiled with this model might incur emulation overhead on EV4, EV5,
and EV56 processors. |
Note
This directive is for use only by compilers. |
