clc: rework optional subgroup feature

OpenCL 3.0 core requires __opencl_c_subgroups to be set, the OpenCL
cl_khr_subgroups extenions can only be enabled if and only if the driver
guarentees independent forward progress between subgroups.

See CL_DEVICE_SUB_GROUP_INDEPENDENT_FORWARD_PROGRESS for more information.

Signed-off-by: Karol Herbst <git@karolherbst.de>
Reviewed-by: Nora Allen <blackcatgames@protonmail.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22893>

src/compiler/clc/clc.h

@@ -58,7 +58,12 @@ struct clc_optional_features {
    bool images_write_3d;
    bool integer_dot_product;
    bool intel_subgroups;
+   /* OpenCL core subgroups */
    bool subgroups;
+   /* OpenCL extension cl_khr_subgroups, which requires independent forward
+    * progress
+    */
+   bool subgroups_ifp;
 };
 
 struct clc_compile_args {

src/compiler/clc/clc_helpers.cpp

@@ -927,6 +927,10 @@ clc_compile_to_llvm_module(LLVMContext &llvm_ctx,
       c->getTargetOpts().OpenCLExtensionsAsWritten.push_back("+cl_intel_subgroups");
    }
    if (args->features.subgroups) {
+      c->getTargetOpts().OpenCLExtensionsAsWritten.push_back("+__opencl_c_subgroups");
+   }
+   if (args->features.subgroups_ifp) {
+      assert(args->features.subgroups);
       c->getTargetOpts().OpenCLExtensionsAsWritten.push_back("+cl_khr_subgroups");
    }
 #endif

src/gallium/frontends/rusticl/core/device.rs

@@ -901,6 +901,7 @@ impl Device {
             integer_dot_product: true,
             intel_subgroups: false,
             subgroups: false,
+            subgroups_ifp: false,
         }
     }
 }

src/intel/compiler/intel_clc.c

@@ -437,6 +437,7 @@ int main(int argc, char **argv)
             .fp16 = true,
             .intel_subgroups = true,
             .subgroups = true,
+            .subgroups_ifp = true,
          },
          .args = util_dynarray_begin(&clang_args),
          .num_args = util_dynarray_num_elements(&clang_args, char *),