Internals reference

OperationType is an @enum for classifying supported operations that can appear in @avx blocks. Type LoopVectorization.OperationType to see the different types.

An operation setting a variable to a constant value (e.g., a = 0.0)

An operation setting a variable from a memory location (e.g., a = A[i,j])

An operation computing a new value from one or more variables (e.g., a = b + c)

An operation storing a value to a memory location (e.g., A[i,j] = a)

loopvalue indicates an loop variable (i in for i in ...). These are the "parents" of compute operations that involve the loop variables.

Operation

A structure to encode a particular action occuring inside an @avx block.

Fields

• identifier::Int64

  A unique identifier for this operation. identifer(op::Operation) returns the index of this operation within operations(ls::LoopSet).

• variable::Symbol

  The name of the variable storing the result of this operation. For a = val this would be :a. For array assignments A[i,j] = val this would be :A.

• elementbytes::Int64

  Intended to be the size of the result, in bytes. Often inaccurate, not to be relied on.

• instruction::LoopVectorization.Instruction

  The specific operator, e.g., identity or +

• node_type::LoopVectorization.OperationType

  The OperationType associated with this operation

• dependencies::Array{Symbol,1}

  The loop variables this operation depends on

• reduced_deps::Array{Symbol,1}

  Additional loop dependencies that must execute before this operation can be performed successfully (often needed in reductions)

• parents::Array{LoopVectorization.Operation,1}

  Operations whose result this operation depends on

• children::Array{LoopVectorization.Operation,1}

  Operations who depend on this result

• ref::LoopVectorization.ArrayReferenceMeta

  For memload or memstore, encodes the array location

• mangledvariable::Symbol

  gensymmed name of result.

• reduced_children::Array{Symbol,1}

  Loop variables that consumers of this operation depend on. Often used in reductions to replicate assignment of initializers when unrolling.

• u₁unrolled::Bool

  Cached value for whether u₁loopsym ∈ loopdependencies(op)

• u₂unrolled::Bool

  Cached value for whether u₂loopsym ∈ loopdependencies(op)

• vectorized::Bool

  Cached value for whether vectorized ∈ loopdependencies(op)

Example

julia> using LoopVectorization

julia> AmulBq = :(for m ∈ 1:M, n ∈ 1:N
           C[m,n] = zero(eltype(B))
           for k ∈ 1:K
               C[m,n] += A[m,k] * B[k,n]
           end
       end);

julia> lsAmulB = LoopVectorization.LoopSet(AmulBq);

julia> LoopVectorization.operations(lsAmulB)
6-element Vector{LoopVectorization.Operation}:
 var"##RHS#245" = var"##zero#246"
 C[m, n] = var"##RHS#245"
 var"##tempload#248" = A[m, k]
 var"##tempload#249" = B[k, n]
 var"##RHS#245" = LoopVectorization.vfmadd(var"##tempload#248", var"##tempload#249", var"##RHS#245")
 var"##RHS#245" = LoopVectorization.identity(var"##RHS#245")

Each one of these lines is a pretty-printed Operation.

Instruction

Instruction represents a function via its module and symbol. It is similar to a GlobalRef and may someday be replaced by GlobalRef.

InstructionCost

Store parameters related to performance for individual CPU instructions.

• scaling::Float64

  A flag indicating how instruction cost scales with vector width (128, 256, or 512 bits)

• scalar_reciprocal_throughput::Float64

  The number of clock cycles per operation when many of the same operation are repeated in sequence. Think of it as the inverse of the flow rate at steady-state. It is typically ≤ the scalar_latency.

• scalar_latency::Int64

  The minimum delay, in clock cycles, associated with the instruction. Think of it as the delay from turning on a faucet to when water starts coming out the end of the pipe. See also scalar_reciprocal_throughput.

• register_pressure::Int64

  Number of floating-point registered used

ArrayReference

A type for encoding an array reference A[i,j] occurring inside an @avx block.

Fields

• array::Symbol

  The array variable

• indices::Array{Symbol,1}

  The list of indices (e.g., [:i, :j]), or name(op) for computed indices.

• offsets::Array{Int8,1}

  Index offset, e.g., a[i+7] would store the 7. offsets is also used to help identify opportunities for avoiding reloads, for example in y[i] = x[i] - x[i-1], the previous load x[i-1] can be "carried over" to the next iteration. Only used for small (Int8) offsets.

ArrayReferenceMeta

A type similar to ArrayReference but holding additional information.

Fields

• ref::LoopVectorization.ArrayReference

  The ArrayReference

• loopedindex::Array{Bool,1}

  A vector of Bools indicating whether each index is a loop variable (false for operation-computed indices)

• ptr::Symbol

  Variable holding the pointer to the array's underlying storage

ArrayRefStruct

A condensed representation of an ArrayReference. It supports array-references with up to 8 indexes, where the data for each consecutive index is packed into corresponding 8-bit fields of index_types (storing the enum IndexType), indices (the id for each index symbol), and offsets (currently unused).

OperationStruct

A condensed representation of an Operation.