Add nextafter intrinsic

Author: christiangnrd

src/device/intrinsics/math.jl

@@ -274,6 +274,11 @@ end
 @device_override Base.trunc(x::Float32) = ccall("extern air.trunc.f32", llvmcall, Cfloat, (Cfloat,), x)
 @device_override Base.trunc(x::Float16) = ccall("extern air.trunc.f16", llvmcall, Float16, (Float16,), x)
 
+@static if Metal.is_macos(v"14")
+    @device_function nextafter(x::Float32, y::Float32) = ccall("extern air.nextafter.f32", llvmcall, Cfloat, (Cfloat, Cfloat), x, y)
+    @device_function nextafter(x::Float16, y::Float16) = ccall("extern air.nextafter.f16", llvmcall, Float16, (Float16, Float16), x, y)
+end
+
 # hypot without use of double
 #
 # taken from Cosmopolitan Libc
@@ -418,7 +423,7 @@ end
     j = fma(1.442695f0, a, 12582912.0f0)
     j = j - 12582912.0f0
     i = unsafe_trunc(Int32, j)
-    f = fma(j, -6.93145752f-1, a) # log_2_hi 
+    f = fma(j, -6.93145752f-1, a) # log_2_hi
     f = fma(j, -1.42860677f-6, f) # log_2_lo
 
     # approximate r = exp(f)-1 on interval [-log(2)/2, +log(2)/2]

test/device/intrinsics.jl

@@ -164,10 +164,27 @@ end
     vecF = Array(SpecialFunctions.erfinv.(bufferF))
     @test vecF ≈ SpecialFunctions.erfinv.(f)
 
-    f = collect(LinRange(nextfloat(-88f0), 88f0, 100))
-    bufferF = MtlArray(f)
-    vecF = Array(expm1.(bufferF))
-    @test vecF ≈ expm1.(f)
+    g = collect(LinRange(nextfloat(-88.0f0), 88.0f0, 100))
+    bufferG = MtlArray(g)
+    vecG = Array(expm1.(bufferG))
+    @test vecG ≈ expm1.(g)
+
+    if Metal.is_macos(v"14")
+        function nextafter_test(X, y)
+            idx = thread_position_in_grid_1d()
+            X[idx] = Metal.nextafter(X[idx], y)
+            return nothing
+        end
+        h = rand(Float32, 1)
+        bufferH = MtlArray(h)
+        @metal nextafter_test(bufferH, typemax(Float32))
+        synchronize()
+        @test Array(bufferH) ≈ nextfloat.(h)
+
+        @metal nextafter_test(bufferH, typemin(Float32))
+        synchronize()
+        @test Array(bufferH) ≈ h
+    end
 end
 
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