SSA is an IntermediateLanguage, translated from SXML by ClosureConvert, optimized by SSASimplify, and translated by ToSSA2 to SSA2.

Description

SSA is a FirstOrder, SimplyTyped IntermediateLanguage. It is the main IntermediateLanguage used for optimizations.

An SSA program consists of a collection of datatype declarations, a sequence of global statements, and a collection of functions, along with a distinguished "main" function. Each function consists of a collection of basic blocks, where each basic block is a sequence of statements ending with some control transfer.

Implementation

ssa.sig ssa.fun
ssa-tree.sig ssa-tree.fun

Type Checking

Type checking of a SSA program verifies the following:

• no duplicate definitions (tycons, cons, vars, labels, funcs)

• no out of scope references (tycons, cons, vars, labels, funcs)

• variable definitions dominate variable uses

• case transfers are exhaustive and irredundant

• Enter/Leave profile statements match

• "traditional" well-typedness

type-check.sig type-check.fun

Details and Notes

SSA is an abbreviation for Static Single Assignment.