Merge pull request #21312 from JuliaLang/teh/unsafe_trunc_float16

Support `unsafe_trunc(<:Integer, x::Float16)`

Author: timholy

base/float.jl

@@ -275,12 +275,14 @@ float{T<:Number}(::Type{T}) = typeof(float(zero(T)))
 
 for Ti in (Int8, Int16, Int32, Int64)
     @eval begin
+        unsafe_trunc(::Type{$Ti}, x::Float16) = unsafe_trunc($Ti, Float32(x))
         unsafe_trunc(::Type{$Ti}, x::Float32) = fptosi($Ti, x)
         unsafe_trunc(::Type{$Ti}, x::Float64) = fptosi($Ti, x)
     end
 end
 for Ti in (UInt8, UInt16, UInt32, UInt64)
     @eval begin
+        unsafe_trunc(::Type{$Ti}, x::Float16) = unsafe_trunc($Ti, Float32(x))
         unsafe_trunc(::Type{$Ti}, x::Float32) = fptoui($Ti, x)
         unsafe_trunc(::Type{$Ti}, x::Float64) = fptoui($Ti, x)
     end
@@ -314,6 +316,8 @@ function unsafe_trunc(::Type{Int128}, x::Float32)
     copysign(unsafe_trunc(UInt128,x) % Int128, x)
 end
 
+unsafe_trunc(::Type{UInt128}, x::Float16) = unsafe_trunc(UInt128, Float32(x))
+unsafe_trunc(::Type{Int128}, x::Float16) = unsafe_trunc(Int128, Float32(x))
 
 # matches convert methods
 # also determines floor, ceil, round

test/float16.jl

@@ -49,6 +49,11 @@ g = Float16(1.)
 @test floor(Float16(1)) === Float16(1)
 @test ceil(Float16(0.1)) == ceil(0.1)
 @test ceil(Float16(0.9)) == ceil(0.9)
+@test unsafe_trunc(UInt8, Float16(3)) === 0x03
+@test unsafe_trunc(Int16, Float16(3)) === Int16(3)
+@test unsafe_trunc(UInt128, Float16(3)) === UInt128(3)
+@test unsafe_trunc(Int128, Float16(3)) === Int128(3)
+@test unsafe_trunc(Int16, NaN16) === Int16(0)  #18771
 @test fma(Float16(0.1),Float16(0.9),Float16(0.5)) ≈ fma(0.1,0.9,0.5)
 @test muladd(Float16(0.1),Float16(0.9),Float16(0.5)) ≈ muladd(0.1,0.9,0.5)
 @test convert(Int128,Float16(-1.0)) == Int128(-1)