Add unsafe macro to eliminate bounds checking

Author: timholy

benchmark/benchmarks.jl

@@ -14,6 +14,12 @@ update(x) = for i in indices(x,1); x[i] = x[i] + i; end
 update2d(x) = for j in indices(x,2); for i in indices(x,1); x[i,j] = x[i,j] + i + j; end; end
 update_eachindex(x) = for i in eachindex(x); x[i] = x[i] + i; end
 
+unsafe_fill(x) = @unsafe(for i in indices(x,1); x[i] = i; end)
+unsafe_fill2d(x) = @unsafe(for j in indices(x,2); for i in indices(x,1); x[i,j] = i + j; end; end)
+unsafe_update(x) = @unsafe(for i in indices(x,1); x[i] = x[i] + i; end)
+unsafe_update2d(x) = @unsafe(for j in indices(x,2); for i in indices(x,1); x[i,j] = x[i,j] + i + j; end; end)
+unsafe_update_eachindex(x) = @unsafe(for i in eachindex(x); x[i] = x[i] + i; end)
+
 @show @benchmark fill(x)
 @show @benchmark fill(y)
 @show @benchmark fill2d(x2d)
@@ -24,3 +30,14 @@ update_eachindex(x) = for i in eachindex(x); x[i] = x[i] + i; end
 @show @benchmark update2d(y2d)
 @show @benchmark update_eachindex(x)
 @show @benchmark update_eachindex(y)
+
+@show @benchmark unsafe_fill(x)
+@show @benchmark unsafe_fill(y)
+@show @benchmark unsafe_fill2d(x2d)
+@show @benchmark unsafe_fill2d(y2d)
+@show @benchmark unsafe_update(x)
+@show @benchmark unsafe_update(y)
+@show @benchmark unsafe_update2d(x2d)
+@show @benchmark unsafe_update2d(y2d)
+@show @benchmark unsafe_update_eachindex(x)
+@show @benchmark unsafe_update_eachindex(y)

src/OffsetArrays.jl

@@ -6,7 +6,7 @@ Base.@deprecate_binding (..) Colon()
 
 using Base: Indices, LinearSlow, LinearFast, tail
 
-export OffsetArray
+export OffsetArray, @unsafe
 
 immutable OffsetArray{T,N,AA<:AbstractArray} <: AbstractArray{T,N}
     parent::AA
@@ -128,4 +128,37 @@ _offset(out, ::Tuple{}, ::Tuple{}) = out
 indexoffset(r::Range) = first(r) - 1
 indexoffset(i::Integer) = 0
 
+macro unsafe(ex)
+    esc(unsafe(ex))
+end
+unsafe(ex) = ex
+function unsafe(ex::Expr)
+    if ex.head ∈ (:+=, :-=, :*=, :/=)
+        ex = Expr(:(=), ex.args[1], Expr(:call, Symbol(string(ex.head)[1]), ex.args...))
+    end
+    if ex.head == :(=)
+        a = ex.args[1]
+        if isa(a, Expr) && (a::Expr).head == :ref
+            # setindex!
+            newargs = map(unsafe, ex.args[2:end])
+            @assert length(newargs) == 1
+            return Expr(:call, :(OffsetArrays.unsafe_setindex!), (a::Expr).args[1], newargs[1], (a::Expr).args[2:end]...)
+        end
+    end
+    newargs = map(unsafe, ex.args)
+    if ex.head == :ref
+        # getindex
+        return Expr(:call, :(OffsetArrays.unsafe_getindex), newargs...)
+    end
+    Expr(ex.head, newargs...)
+end
+
+@inline unsafe_getindex(a::AbstractArray, I...) = (@inbounds ret = a[I...]; ret)
+@inline unsafe_setindex!(a::AbstractArray, val, I...) = (@inbounds a[I...] = val; val)
+
+@inline unsafe_getindex(a::OffsetArray, I::Int...) = (@inbounds ret = parent(a)[offset(a.offsets, I)...]; ret)
+@inline unsafe_setindex!(a::OffsetArray, val, I::Int...) = (@inbounds parent(a)[offset(a.offsets, I)...] = val; val)
+@inline unsafe_getindex(a::OffsetArray, I...) = unsafe_getindex(a, Base.IteratorsMD.flatten(I)...)
+@inline unsafe_setindex!(a::OffsetArray, val, I...) = unsafe_setindex!(a, val, Base.IteratorsMD.flatten(I)...)
+
 end # module

test/runtests.jl

@@ -323,3 +323,19 @@ B = ones(1:3, -1:1)
 B = fill(5, 1:3, -1:1)
 @test indices(B) == (1:3,-1:1)
 @test all(B.==5)
+
+# @unsafe
+a = OffsetArray(zeros(7), -3:3)
+unsafe_fill!(x) = @unsafe(for i in indices(x,1); x[i] = i; end)
+function unsafe_sum(x)
+    s = zero(eltype(x))
+    @unsafe for i in indices(x,1)
+        s += x[i]
+    end
+    s
+end
+unsafe_fill!(a)
+for i = -3:3
+    @test a[i] == i
+end
+@test unsafe_sum(a) == 0