Define quirks for complex sqrt (#374)

src/device/quirks.jl

@@ -10,6 +10,17 @@ end
     @print_and_throw "This operation requires a complex input to return a complex result"
 @device_override @noinline Base.Math.throw_exp_domainerror(x) =
     @print_and_throw "Exponentiation yielding a complex result requires a complex argument"
+@device_override function Base.Math.exponent(x::T) where T<:Base.IEEEFloat
+    xs = reinterpret(Unsigned, x) & ~Base.sign_mask(T)
+    xs >= Base.exponent_mask(T) && @print_and_throw "Cannot be NaN or Inf."
+    k = Int(xs >> Base.significand_bits(T))
+    if k == 0 # x is subnormal
+        xs == 0 && @print_and_throw "Cannot be ±0.0."
+        m = leading_zeros(xs) - Base.exponent_bits(T)
+        k = 1 - m
+    end
+    return k - Base.exponent_bias(T)
+end
 
 # intfuncs.jl
 @device_override @noinline Base.throw_domerr_powbysq(::Any, p) =
@@ -57,3 +68,18 @@ end
         @print_and_throw "Out-of-bounds access of scalar value"
     x
 end
+
+# complex.jl
+@device_override function Base.ssqs(x::T, y::T) where T<:Real
+    k::Int = 0
+    ρ = x*x + y*y
+    if !isfinite(ρ) && (isinf(x) || isinf(y))
+        ρ = convert(T, Inf)
+    elseif isinf(ρ) || (ρ==0 && (x!=0 || y!=0)) || ρ<nextfloat(zero(T))/(2*eps(T)^2)
+        m::T = max(abs(x), abs(y))
+        k = m==0 ? 0 : exponent(m)
+        xk, yk = ldexp(x,-k), ldexp(y,-k)
+        ρ = xk*xk + yk*yk
+    end
+    ρ, k
+end

test/device/intrinsics.jl

@@ -161,6 +161,15 @@ end
 
 ############################################################################################
 
+@testset "complex" begin
+    a = rand(ComplexF32,4)
+    bufferA = MtlArray(a)
+    vecA = Array(sqrt.(bufferA))
+    @test vecA ≈ sqrt.(a)
+end
+
+############################################################################################
+
 @testset "synchronization" begin
     # host/device synchronization
     let