anv: Add support for SPIR-V 1.3 subgroup operations

This requires us to bump the subgroup size to 32 for all shader stages
because Vulkan requires that to be a physical device query.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/intel/compiler/brw_compiler.h

@@ -113,6 +113,14 @@ struct brw_compiler {
    bool supports_pull_constants;
 };
 
+/**
+ * We use a constant subgroup size of 32.  It really only needs to be a
+ * maximum and, since we do SIMD32 for compute shaders in some cases, it
+ * needs to be at least 32.  SIMD8 and SIMD16 shaders will still claim a
+ * subgroup size of 32 but will act as if 16 or 24 of those channels are
+ * disabled.
+ */
+#define BRW_SUBGROUP_SIZE 32
 
 /**
  * Program key structures.

src/intel/compiler/brw_nir.c

@@ -650,8 +650,7 @@ brw_preprocess_nir(const struct brw_compiler *compiler, nir_shader *nir)
    OPT(nir_lower_system_values);
 
    const nir_lower_subgroups_options subgroups_options = {
-      .subgroup_size = nir->info.stage == MESA_SHADER_COMPUTE ? 32 :
-                       nir->info.stage == MESA_SHADER_FRAGMENT ? 16 : 8,
+      .subgroup_size = BRW_SUBGROUP_SIZE,
       .ballot_bit_size = 32,
       .lower_to_scalar = true,
       .lower_subgroup_masks = true,