@(require_target_feature=<string>) @(enable_target_feature=<string>)

require_target_feature - required by the target micro-architecture
enable_target_feature - will be enabled for the specified procedure only

src/build_settings.cpp

@@ -256,7 +256,6 @@ struct BuildContext {
 	String extra_linker_flags;
 	String extra_assembler_flags;
 	String microarch;
-	String target_features;
 	BuildModeKind build_mode;
 	bool   generate_docs;
 	i32    optimization_level;
@@ -320,6 +319,10 @@ struct BuildContext {
 
 	PtrMap<char const *, ExactValue> defined_values;
 
+	BlockingMutex target_features_mutex;
+	StringSet target_features_set;
+	String target_features_string;
+
 };
 
 gb_global BuildContext build_context = {0};
@@ -1197,6 +1200,100 @@ void init_build_context(TargetMetrics *cross_target) {
 #include "microsoft_craziness.h"
 #endif
 
+
+Array<String> split_by_comma(String const &list) {
+	isize n = 1;
+	for (isize i = 0; i < list.len; i++) {
+		if (list.text[i] == ',') {
+			n++;
+		}
+	}
+	auto res = array_make<String>(heap_allocator(), n);
+
+	String s = list;
+	for (isize i = 0; i < n; i++) {
+		isize m = string_index_byte(s, ',');
+		if (m < 0) {
+			res[i] = s;
+			break;
+		}
+		res[i] = substring(s, 0, m);
+		s = substring(s, m+1, s.len);
+	}
+	return res;
+}
+
+bool check_target_feature_is_valid(TokenPos pos, String const &feature) {
+	// TODO(bill): check_target_feature_is_valid
+	return true;
+}
+
+bool check_target_feature_is_enabled(TokenPos pos, String const &target_feature_list) {
+	BuildContext *bc = &build_context;
+	mutex_lock(&bc->target_features_mutex);
+	defer (mutex_unlock(&bc->target_features_mutex));
+
+	auto items = split_by_comma(target_feature_list);
+	array_free(&items);
+	for_array(i, items) {
+		String const &item = items.data[i];
+		if (!check_target_feature_is_valid(pos, item)) {
+			error(pos, "Target feature '%.*s' is not valid", LIT(item));
+			return false;
+		}
+		if (!string_set_exists(&bc->target_features_set, item)) {
+			error(pos, "Target feature '%.*s' is not enabled", LIT(item));
+			return false;
+		}
+	}
+
+	return true;
+}
+
+void enable_target_feature(TokenPos pos, String const &target_feature_list) {
+	BuildContext *bc = &build_context;
+	mutex_lock(&bc->target_features_mutex);
+	defer (mutex_unlock(&bc->target_features_mutex));
+
+	auto items = split_by_comma(target_feature_list);
+	array_free(&items);
+	for_array(i, items) {
+		String const &item = items.data[i];
+		if (!check_target_feature_is_valid(pos, item)) {
+			error(pos, "Target feature '%.*s' is not valid", LIT(item));
+		}
+	}
+}
+
+
+char const *target_features_set_to_cstring(gbAllocator allocator, bool with_quotes) {
+	isize len = 0;
+	for_array(i, build_context.target_features_set.entries) {
+		if (i != 0) {
+			len += 1;
+		}
+		String feature = build_context.target_features_set.entries[i].value;
+		len += feature.len;
+		if (with_quotes) len += 2;
+	}
+	char *features = gb_alloc_array(allocator, char, len+1);
+	len = 0;
+	for_array(i, build_context.target_features_set.entries) {
+		if (i != 0) {
+			features[len++] = ',';
+		}
+
+		if (with_quotes) features[len++] = '"';
+		String feature = build_context.target_features_set.entries[i].value;
+		gb_memmove(features, feature.text, feature.len);
+		len += feature.len;
+		if (with_quotes) features[len++] = '"';
+	}
+	features[len++] = 0;
+
+	return features;
+}
+
 // NOTE(Jeroen): Set/create the output and other paths and report an error as appropriate.
 // We've previously called `parse_build_flags`, so `out_filepath` should be set.
 bool init_build_paths(String init_filename) {
@@ -1206,6 +1303,9 @@ bool init_build_paths(String init_filename) {
 	// NOTE(Jeroen): We're pre-allocating BuildPathCOUNT slots so that certain paths are always at the same enumerated index.
 	array_init(&bc->build_paths, permanent_allocator(), BuildPathCOUNT);
 
+	string_set_init(&bc->target_features_set, heap_allocator(), 1024);
+	mutex_init(&bc->target_features_mutex);
+
 	// [BuildPathMainPackage] Turn given init path into a `Path`, which includes normalizing it into a full path.
 	bc->build_paths[BuildPath_Main_Package] = path_from_string(ha, init_filename);
 
@@ -1382,5 +1482,10 @@ bool init_build_paths(String init_filename) {
 		return false;
 	}
 
+	if (bc->target_features_string.len != 0) {
+		enable_target_feature({}, bc->target_features_string);
+	}
+
 	return true;
-}
+}
+

src/check_decl.cpp

@@ -899,6 +899,18 @@ void check_proc_decl(CheckerContext *ctx, Entity *e, DeclInfo *d) {
 		}
 	}
 
+	if (ac.require_target_feature.len != 0 && ac.enable_target_feature.len != 0) {
+		error(e->token, "Attributes @(require_target_feature=...) and @(enable_target_feature=...) cannot be used together");
+	} else if (ac.require_target_feature.len != 0) {
+		if (check_target_feature_is_enabled(e->token.pos, ac.require_target_feature)) {
+			e->Procedure.target_feature = ac.require_target_feature;
+		} else {
+			e->Procedure.target_feature_disabled = true;
+		}
+	} else if (ac.enable_target_feature.len != 0) {
+		enable_target_feature(e->token.pos, ac.enable_target_feature);
+		e->Procedure.target_feature = ac.enable_target_feature;
+	}
 
 	switch (e->Procedure.optimization_mode) {
 	case ProcedureOptimizationMode_None:

src/checker.cpp

@@ -3207,6 +3207,22 @@ DECL_ATTRIBUTE_PROC(proc_decl_attribute) {
 			}
 		}
 		return true;
+	} else if (name == "require_target_feature") {
+		ExactValue ev = check_decl_attribute_value(c, value);
+		if (ev.kind == ExactValue_String) {
+			ac->require_target_feature = ev.value_string;
+		} else {
+			error(elem, "Expected a string value for '%.*s'", LIT(name));
+		}
+		return true;
+	} else if (name == "enable_target_feature") {
+		ExactValue ev = check_decl_attribute_value(c, value);
+		if (ev.kind == ExactValue_String) {
+			ac->enable_target_feature = ev.value_string;
+		} else {
+			error(elem, "Expected a string value for '%.*s'", LIT(name));
+		}
+		return true;
 	}
 	return false;
 }

src/checker.hpp

@@ -124,6 +124,9 @@ struct AttributeContext {
 	String  objc_name;
 	bool    objc_is_class_method;
 	Type *  objc_type;
+
+	String require_target_feature; // required by the target micro-architecture
+	String enable_target_feature;  // will be enabled for the procedure only
 };
 
 AttributeContext make_attribute_context(String link_prefix) {

src/entity.cpp

@@ -233,10 +233,12 @@ struct Entity {
 			String  link_name;
 			String  link_prefix;
 			DeferredProcedure deferred_procedure;
-			bool    is_foreign;
-			bool    is_export;
-			bool    generated_from_polymorphic;
 			ProcedureOptimizationMode optimization_mode;
+			bool    is_foreign                 : 1;
+			bool    is_export                  : 1;
+			bool    generated_from_polymorphic : 1;
+			bool    target_feature_disabled    : 1;
+			String  target_feature;
 		} Procedure;
 		struct {
 			Array<Entity *> entities;

src/llvm_backend.cpp

@@ -1332,8 +1332,8 @@ void lb_generate_code(lbGenerator *gen) {
 		}
 	}
 
-	if (build_context.target_features.len != 0) {
-		llvm_features = alloc_cstring(permanent_allocator(), build_context.target_features);
+	if (build_context.target_features_set.entries.count != 0) {
+		llvm_features = target_features_set_to_cstring(permanent_allocator(), false);
 	}
 
 	// GB_ASSERT_MSG(LLVMTargetHasAsmBackend(target));

src/llvm_backend_proc.cpp

@@ -169,6 +169,19 @@ lbProcedure *lb_create_procedure(lbModule *m, Entity *entity, bool ignore_body)
 		}
 	}
 
+	if (!entity->Procedure.target_feature_disabled &&
+	    entity->Procedure.target_feature.len != 0) {
+	    	auto features = split_by_comma(entity->Procedure.target_feature);
+		for_array(i, features) {
+			String feature = features[i];
+			LLVMAttributeRef ref = LLVMCreateStringAttribute(
+				m->ctx,
+				cast(char const *)feature.text, cast(unsigned)feature.len,
+				"", 0);
+			LLVMAddAttributeAtIndex(p->value, LLVMAttributeIndex_FunctionIndex, ref);
+		}
+	}
+
 	if (entity->flags & EntityFlag_Cold) {
 		lb_add_attribute_to_proc(m, p->value, "cold");
 	}

src/main.cpp

@@ -1376,8 +1376,8 @@ bool parse_build_flags(Array<String> args) {
 						}
 						case BuildFlag_TargetFeatures: {
 							GB_ASSERT(value.kind == ExactValue_String);
-							build_context.target_features = value.value_string;
-							string_to_lower(&build_context.target_features);
+							build_context.target_features_string = value.value_string;
+							string_to_lower(&build_context.target_features_string);
 							break;
 						}
 						case BuildFlag_RelocMode: {

src/string.cpp

@@ -157,6 +157,15 @@ int string_compare(String const &x, String const &y) {
 	return 0;
 }
 
+isize string_index_byte(String const &s, u8 x) {
+	for (isize i = 0; i < s.len; i++) {
+		if (s.text[i] == x) {
+			return i;
+		}
+	}
+	return -1;
+}
+
 GB_COMPARE_PROC(string_cmp_proc) {
 	String x = *(String *)a;
 	String y = *(String *)b;