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[Caml-list] Pointers needed for optimization problem.
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Date: 2002-08-22 (02:18)
From: Pal-Kristian Engstad <engstad@n...>
Subject: [Caml-list] Pointers needed for optimization problem.

I'm interested in solving a problem I have with automatically generating 
optimal (vector) floating point code. In other words, I want to code a caml 
program that transforms the input description into assembly instructions. For 
regular floating point operations, a good compiler should be able to optimize 
the code:
	r := A * x * x + B * x + C

into (if multiplication is more expensive than adds):

	t := A * x
	t := t + B
	t := t * x
	t := t + B
	r := (A * x + B) * x + C

Now, this is fairly trivial to do, but if you have an architecture with SIMD 
vector floating point registers and opcodes, a whole range of new interesting 
optimizations can be done. With vector registers, I mean registers that have 
up to 4 floating point values. For instance, a 4-vector times a 4-by-4 matrix 
operation can be coded as:

	acc.xyzw := mtxrow[0].xyzw * vec.x
	acc.xyzw += mtxrow[1].xyzw * vec.y
	acc.xyzw += mtxrow[2].xyzw * vec.z
	res.xyzw = acc.xyzw + mtxrow[3].xyzw * vec.w

Here, each line represent one assembly instruction.

So, what I am looking for is basically pointers to literature that deal with 
issues like these, and since OCaml is a great language for language 
transformations I thought someone on this list would be able to point me in 
the right direction. I _have_ been searching on the net, but I guess I don't 
know the right keywords to search on.

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