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Sun May 2 15:47:20 EDT 2010

SSA IN/OUT parameterization

In the light of previous post, what is the problem?  All code I'm
using depends on SSA form, but what I want is an abstracted SSA/DSN
form that allows me to bind network outputs to externally allocated
nodes.

So this essentially needs a functional representation.  An SSA
structure is a function that has sharing and internal node allocation
figured out (i.e. more abstractly it can be parameterized by an
internal node allocator), but can be patched into a larger node
network.

So, SSA is form is  NodeAlloc -> Inputs -> Outputs -> Network.

Actually, it's simple: nodes need to be parameterized, the rest of the
behaviour can be fixed.

Roadmap:
    - abstract node-alloc
    - parameterize output assign (default = node alloc)

So, in Term.hs, `nameNodes' is where the intermediate nodes are named.


This is mostly a wrapper around `nameShared' from Shared.hs while
shared node construction is performed separately using the
`extendShared' function.

Approach: stick to numeric node tags, but replace the [0..]  sequence
by a parameter `regnums'.  OK.

Next to open up: Function.

data Let      = Let      String String [String]  deriving Show
data Function = Function [String] [Let] [String] 

This is already fully serialized, and all node names are Strings.  It
might be simpler to keep this representation, and focus on performing
substitutions on the symbol names.


*Main> test1
in:  dummy
r0 <- mul ar br
r1 <- mul ai bi
r2 <- negate r1
r3 <- add r0 r2
r4 <- mul ar bi
r5 <- mul ai br
r6 <- add r4 r5
out: r3 r6


Maybe a guiding remark: do I want to keep an SSA-converted network
around to re-use, or is it simpler to recompile from the memo-term
form and use only Haskell function composition?

What purpose does `Function' serve?  To decouple the Term form from
the C/ASM code generation?

I'm making this too difficult.  Let's start over.

Maybe I need to pick one and stick with it?  Compose only in Haskell,
or also in the lower-level code?  This might be important for re-using
function composition in the low-level language instead of using only
macro expansion.


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