replace copysign.f16 for pocl backend

companion PR to JuliaGPU/GPUCompiler.jl#722

Author: simeonschaub

.github/workflows/Test.yml

@@ -135,6 +135,7 @@ jobs:
           echo 'default_memory_backend="${{ matrix.memory_backend }}"' >> test/LocalPreferences.toml
           julia --project -e '
             using Pkg
+            Pkg.add(name="GPUCompiler", rev="sds/replace_copysign_f16")
             Pkg.develop(path="lib/intrinsics")'
 
       - name: Test OpenCL.jl

src/compiler/compilation.jl

@@ -47,9 +47,10 @@ end
 @noinline function _compiler_config(dev; kernel=true, name=nothing, always_inline=false, kwargs...)
     supports_fp16 = "cl_khr_fp16" in dev.extensions
     supports_fp64 = "cl_khr_fp64" in dev.extensions
+    replace_copysign_f16 = dev.platform.name == "Portable Computing Language"
 
     # create GPUCompiler objects
-    target = SPIRVCompilerTarget(; supports_fp16, supports_fp64, validate=true, kwargs...)
+    target = SPIRVCompilerTarget(; supports_fp16, supports_fp64, replace_copysign_f16, validate=true, kwargs...)
     params = OpenCLCompilerParams()
     CompilerConfig(target, params; kernel, name, always_inline)
 end