disable fma on Windows

See #31.

Author: simonbyrne

src/Quadmath.jl

@@ -348,8 +348,12 @@ atan(x::Float128, y::Float128) =
 sincos(x::Float128) = (sin(x), cos(x))
 
 ## misc
-fma(x::Float128, y::Float128, z::Float128) =
-    Float128(@ccall(libquadmath.fmaq(x::Cfloat128, y::Cfloat128, z::Cfloat128)::Cfloat128))
+@static if !Sys.iswindows()
+    # disable fma on Windows until rounding mode issue fixed
+    # https://github.com/JuliaMath/Quadmath.jl/issues/31
+    fma(x::Float128, y::Float128, z::Float128) =
+        Float128(@ccall(libquadmath.fmaq(x::Cfloat128, y::Cfloat128, z::Cfloat128)::Cfloat128))
+end
 
 isnan(x::Float128) = 0 != @ccall(libquadmath.isnanq(x::Cfloat128)::Cint)
 isinf(x::Float128) = 0 != @ccall(libquadmath.isinfq(x::Cfloat128)::Cint)

test/runtests.jl

@@ -121,7 +121,9 @@ end
         @test abs(x) == x
         @test hypot(Float128(3),Float128(4)) == Float128(5)
         @test atan(x,x) ≈ Float128(pi) / 4
-        @test fma(x,x,Float128(-1.0)) ≈ Float128(1)
+        if !Sys.iswindows()
+            @test fma(x,x,Float128(-1.0)) ≈ Float128(1)
+        end
     end
     @testset "complex" begin
         x = sqrt(ComplexF128(1.0 + 1.0im))