PIPS/SAC: SIMD Architecture Compiler

François Ferrand

ENST Bretagne

October 17, 2019

Introduction

This document defines and describes the data structures used by SAC, the SIMD Architecture Compiler. SAC is a new PIPS phase, which allows to generate code optimized for architectures supporting multimedia instruction sets, such as MMX, SSE or VIS.

import entity from "ri.newgen"

import expression from "ri.newgen"

import statement from "ri.newgen"

import reference from "ri.newgen"

import reduction from "reductions_private.newgen"

reductionInfo = persistent reduction x count:int x persistent vector:entity

Opcodes and opcode classes

opcode = name:string x vectorSize:int x argType:int* x cost:float

tabulated opcodeClass = name:string x nbArgs:int x opcodes:opcode*

Statement matching

Statement matching is used to detect “patterns” in the code. It works on the expression tree representing the program. The actual patterns are read from a file, to create a matchTree that is used to efficiently parse the expression tree. This process returns a list of matches, indicating the various opcodes that can thus be generated, and with which arguments.

A patternArg specifies how an argument is to be generated. It can be an integer constant, with the specified value, or extracted from the actual expression tree.

patternArg = static:int + dynamic:unit

A pattern identifies what to generate. It specifies the opcode class corresponding to the pattern, as well as a list that can be used to translate from original statement references or constants to arguments for the opcode.

patternx = class:opcodeClass x args:patternArg*

matchTreeSons = int->matchTree

External operator_id_sons

operator_id_tree = id:int x sons:operator_id_sons

matchTree is a structure used to efficiently identify patterns corresponding to a statement. When traversed, it can thus map a statement to a list of patterns that can be used.

matchTree = patterns:patternx* x sons:matchTreeSons

A pattern can be translated into a match by mapping the arguments properly. The argument list in a match is constructed from the arguments of the statement, following the rules of pattern arguments (list of patternArg).

match = type:opcodeClass x args:expression*

Statement information

simdstatement = opcode x nbArgs:int x vectors:entity[16] x arguments:expression[48]

Transformation

transformation = name:string x vectorLengthOut:int x subwordSizeOut:int x vectorLengthIn:int x subwordSizeIn:int x nbArgs:int x mapping:int[16]