Metal: Improve startup times by using concurrent shader compilation APIs

drivers/metal/metal_objects.h

@@ -57,10 +57,12 @@
 
 #import "servers/rendering/rendering_device_driver.h"
 
+#import <CommonCrypto/CommonDigest.h>
 #import <Foundation/Foundation.h>
 #import <Metal/Metal.h>
 #import <QuartzCore/CAMetalLayer.h>
 #import <simd/simd.h>
+#import <zlib.h>
 #import <initializer_list>
 #import <optional>
 #import <spirv.hpp>
@@ -497,6 +499,76 @@ struct API_AVAILABLE(macos(11.0), ios(14.0)) UniformSet {
 	HashMap<RDC::ShaderStage, id<MTLArgumentEncoder>> encoders;
 };
 
+struct ShaderCacheEntry;
+
+enum class ShaderLoadStrategy {
+	DEFAULT,
+	LAZY,
+};
+
+/**
+ * A Metal shader library.
+ */
+@interface MDLibrary : NSObject
+- (id<MTLLibrary>)library;
+- (NSError *)error;
+- (void)setLabel:(NSString *)label;
+
++ (instancetype)newLibraryWithCacheEntry:(ShaderCacheEntry *)entry
+								  device:(id<MTLDevice>)device
+								  source:(NSString *)source
+								 options:(MTLCompileOptions *)options
+								strategy:(ShaderLoadStrategy)strategy;
+@end
+
+struct SHA256Digest {
+	unsigned char data[CC_SHA256_DIGEST_LENGTH];
+
+	uint32_t hash() const {
+		uint32_t c = crc32(0, data, CC_SHA256_DIGEST_LENGTH);
+		return c;
+	}
+
+	SHA256Digest() {
+		bzero(data, CC_SHA256_DIGEST_LENGTH);
+	}
+
+	SHA256Digest(const char *p_data, size_t p_length) {
+		CC_SHA256(p_data, (CC_LONG)p_length, data);
+	}
+};
+
+template <>
+struct HashMapComparatorDefault<SHA256Digest> {
+	static bool compare(const SHA256Digest &p_lhs, const SHA256Digest &p_rhs) {
+		return memcmp(p_lhs.data, p_rhs.data, CC_SHA256_DIGEST_LENGTH) == 0;
+	}
+};
+
+/**
+ * A cache entry for a Metal shader library.
+ */
+struct ShaderCacheEntry {
+	RenderingDeviceDriverMetal &owner;
+	SHA256Digest key;
+	CharString name;
+	CharString short_sha;
+	RD::ShaderStage stage = RD::SHADER_STAGE_VERTEX;
+	/**
+	 * This reference must be weak, to ensure that when the last strong reference to the library
+	 * is released, the cache entry is freed.
+	 */
+	MDLibrary *__weak library = nil;
+
+	/** Notify the cache that this entry is no longer needed. */
+	void notify_free() const;
+
+	ShaderCacheEntry(RenderingDeviceDriverMetal &p_owner, SHA256Digest p_key) :
+			owner(p_owner), key(p_key) {
+	}
+	~ShaderCacheEntry() = default;
+};
+
 class API_AVAILABLE(macos(11.0), ios(14.0)) MDShader {
 public:
 	CharString name;
@@ -517,15 +589,14 @@ public:
 	} push_constants;
 	MTLSize local = {};
 
-	id<MTLLibrary> kernel;
+	MDLibrary *kernel;
 #if DEV_ENABLED
 	CharString kernel_source;
 #endif
 
 	void encode_push_constant_data(VectorView<uint32_t> p_data, MDCommandBuffer *p_cb) final;
 
-	MDComputeShader(CharString p_name, Vector<UniformSet> p_sets, id<MTLLibrary> p_kernel);
-	~MDComputeShader() override = default;
+	MDComputeShader(CharString p_name, Vector<UniformSet> p_sets, MDLibrary *p_kernel);
 };
 
 class API_AVAILABLE(macos(11.0), ios(14.0)) MDRenderShader final : public MDShader {
@@ -541,8 +612,8 @@ public:
 		} frag;
 	} push_constants;
 
-	id<MTLLibrary> vert;
-	id<MTLLibrary> frag;
+	MDLibrary *vert;
+	MDLibrary *frag;
 #if DEV_ENABLED
 	CharString vert_source;
 	CharString frag_source;
@@ -550,8 +621,7 @@ public:
 
 	void encode_push_constant_data(VectorView<uint32_t> p_data, MDCommandBuffer *p_cb) final;
 
-	MDRenderShader(CharString p_name, Vector<UniformSet> p_sets, id<MTLLibrary> p_vert, id<MTLLibrary> p_frag);
-	~MDRenderShader() override = default;
+	MDRenderShader(CharString p_name, Vector<UniformSet> p_sets, MDLibrary *p_vert, MDLibrary *p_frag);
 };
 
 enum StageResourceUsage : uint32_t {

drivers/metal/metal_objects.mm

@@ -50,9 +50,12 @@
 
 #import "metal_objects.h"
 
+#import "metal_utils.h"
 #import "pixel_formats.h"
 #import "rendering_device_driver_metal.h"
 
+#import <os/signpost.h>
+
 void MDCommandBuffer::begin() {
 	DEV_ASSERT(commandBuffer == nil);
 	commandBuffer = queue.commandBuffer;
@@ -850,7 +853,7 @@ void MDCommandBuffer::_end_blit() {
 	type = MDCommandBufferStateType::None;
 }
 
-MDComputeShader::MDComputeShader(CharString p_name, Vector<UniformSet> p_sets, id<MTLLibrary> p_kernel) :
+MDComputeShader::MDComputeShader(CharString p_name, Vector<UniformSet> p_sets, MDLibrary *p_kernel) :
 		MDShader(p_name, p_sets), kernel(p_kernel) {
 }
 
@@ -868,7 +871,7 @@ void MDComputeShader::encode_push_constant_data(VectorView<uint32_t> p_data, MDC
 	[enc setBytes:ptr length:length atIndex:push_constants.binding];
 }
 
-MDRenderShader::MDRenderShader(CharString p_name, Vector<UniformSet> p_sets, id<MTLLibrary> _Nonnull p_vert, id<MTLLibrary> _Nonnull p_frag) :
+MDRenderShader::MDRenderShader(CharString p_name, Vector<UniformSet> p_sets, MDLibrary *_Nonnull p_vert, MDLibrary *_Nonnull p_frag) :
 		MDShader(p_name, p_sets), vert(p_vert), frag(p_frag) {
 }
 
@@ -1378,3 +1381,204 @@ id<MTLDepthStencilState> MDResourceCache::get_depth_stencil_state(bool p_use_dep
 	}
 	return *val;
 }
+
+static const char *SHADER_STAGE_NAMES[] = {
+	[RD::SHADER_STAGE_VERTEX] = "vert",
+	[RD::SHADER_STAGE_FRAGMENT] = "frag",
+	[RD::SHADER_STAGE_TESSELATION_CONTROL] = "tess_ctrl",
+	[RD::SHADER_STAGE_TESSELATION_EVALUATION] = "tess_eval",
+	[RD::SHADER_STAGE_COMPUTE] = "comp",
+};
+
+void ShaderCacheEntry::notify_free() const {
+	owner.shader_cache_free_entry(key);
+}
+
+@interface MDLibrary ()
+- (instancetype)initWithCacheEntry:(ShaderCacheEntry *)entry;
+- (ShaderCacheEntry *)entry;
+@end
+
+@interface MDLazyLibrary : MDLibrary {
+	id<MTLLibrary> _library;
+	NSError *_error;
+	std::shared_mutex _mu;
+	bool _loaded;
+	id<MTLDevice> _device;
+	NSString *_source;
+	MTLCompileOptions *_options;
+}
+- (instancetype)initWithCacheEntry:(ShaderCacheEntry *)entry
+							device:(id<MTLDevice>)device
+							source:(NSString *)source
+						   options:(MTLCompileOptions *)options;
+@end
+
+@interface MDImmediateLibrary : MDLibrary {
+	id<MTLLibrary> _library;
+	NSError *_error;
+	std::mutex _cv_mutex;
+	std::condition_variable _cv;
+	std::atomic<bool> _complete;
+	bool _ready;
+}
+- (instancetype)initWithCacheEntry:(ShaderCacheEntry *)entry
+							device:(id<MTLDevice>)device
+							source:(NSString *)source
+						   options:(MTLCompileOptions *)options;
+@end
+
+@implementation MDLibrary {
+	ShaderCacheEntry *_entry;
+}
+
++ (instancetype)newLibraryWithCacheEntry:(ShaderCacheEntry *)entry
+								  device:(id<MTLDevice>)device
+								  source:(NSString *)source
+								 options:(MTLCompileOptions *)options
+								strategy:(ShaderLoadStrategy)strategy {
+	switch (strategy) {
+		case ShaderLoadStrategy::DEFAULT:
+			[[fallthrough]];
+		default:
+			return [[MDImmediateLibrary alloc] initWithCacheEntry:entry device:device source:source options:options];
+		case ShaderLoadStrategy::LAZY:
+			return [[MDLazyLibrary alloc] initWithCacheEntry:entry device:device source:source options:options];
+	}
+}
+
+- (ShaderCacheEntry *)entry {
+	return _entry;
+}
+
+- (id<MTLLibrary>)library {
+	CRASH_NOW_MSG("Not implemented");
+	return nil;
+}
+
+- (NSError *)error {
+	CRASH_NOW_MSG("Not implemented");
+	return nil;
+}
+
+- (void)setLabel:(NSString *)label {
+}
+
+- (instancetype)initWithCacheEntry:(ShaderCacheEntry *)entry {
+	self = [super init];
+	_entry = entry;
+	_entry->library = self;
+	return self;
+}
+
+- (void)dealloc {
+	_entry->notify_free();
+}
+
+@end
+
+@implementation MDImmediateLibrary
+
+- (instancetype)initWithCacheEntry:(ShaderCacheEntry *)entry
+							device:(id<MTLDevice>)device
+							source:(NSString *)source
+						   options:(MTLCompileOptions *)options {
+	self = [super initWithCacheEntry:entry];
+	_complete = false;
+	_ready = false;
+
+	__block os_signpost_id_t compile_id = (os_signpost_id_t)(uintptr_t)self;
+	os_signpost_interval_begin(LOG_INTERVALS, compile_id, "shader_compile",
+			"shader_name=%{public}s stage=%{public}s hash=%{public}s",
+			entry->name.get_data(), SHADER_STAGE_NAMES[entry->stage], entry->short_sha.get_data());
+
+	[device newLibraryWithSource:source
+						 options:options
+			   completionHandler:^(id<MTLLibrary> library, NSError *error) {
+				   os_signpost_interval_end(LOG_INTERVALS, compile_id, "shader_compile");
+				   self->_library = library;
+				   self->_error = error;
+				   if (error) {
+					   ERR_PRINT(String(U"Error compiling shader %s: %s").format(entry->name.get_data(), error.localizedDescription.UTF8String));
+				   }
+
+				   {
+					   std::lock_guard<std::mutex> lock(self->_cv_mutex);
+					   _ready = true;
+				   }
+				   _cv.notify_all();
+				   _complete = true;
+			   }];
+	return self;
+}
+
+- (id<MTLLibrary>)library {
+	if (!_complete) {
+		std::unique_lock<std::mutex> lock(_cv_mutex);
+		_cv.wait(lock, [&] { return _ready; });
+	}
+	return _library;
+}
+
+- (NSError *)error {
+	if (!_complete) {
+		std::unique_lock<std::mutex> lock(_cv_mutex);
+		_cv.wait(lock, [&] { return _ready; });
+	}
+	return _error;
+}
+
+@end
+
+@implementation MDLazyLibrary
+- (instancetype)initWithCacheEntry:(ShaderCacheEntry *)entry
+							device:(id<MTLDevice>)device
+							source:(NSString *)source
+						   options:(MTLCompileOptions *)options {
+	self = [super initWithCacheEntry:entry];
+	_device = device;
+	_source = source;
+	_options = options;
+
+	return self;
+}
+
+- (void)load {
+	{
+		std::shared_lock<std::shared_mutex> lock(_mu);
+		if (_loaded) {
+			return;
+		}
+	}
+
+	std::unique_lock<std::shared_mutex> lock(_mu);
+	if (_loaded) {
+		return;
+	}
+
+	ShaderCacheEntry *entry = [self entry];
+
+	__block os_signpost_id_t compile_id = (os_signpost_id_t)(uintptr_t)self;
+	os_signpost_interval_begin(LOG_INTERVALS, compile_id, "shader_compile",
+			"shader_name=%{public}s stage=%{public}s hash=%{public}s",
+			entry->name.get_data(), SHADER_STAGE_NAMES[entry->stage], entry->short_sha.get_data());
+	NSError *error;
+	_library = [_device newLibraryWithSource:_source options:_options error:&error];
+	os_signpost_interval_end(LOG_INTERVALS, compile_id, "shader_compile");
+	_device = nil;
+	_source = nil;
+	_options = nil;
+	_loaded = true;
+}
+
+- (id<MTLLibrary>)library {
+	[self load];
+	return _library;
+}
+
+- (NSError *)error {
+	[self load];
+	return _error;
+}
+
+@end

drivers/metal/metal_utils.h

@@ -31,6 +31,8 @@
 #ifndef METAL_UTILS_H
 #define METAL_UTILS_H
 
+#import <os/log.h>
+
 #pragma mark - Boolean flags
 
 namespace flags {
@@ -78,4 +80,22 @@ static constexpr uint64_t round_up_to_alignment(uint64_t p_value, uint64_t p_ali
 	return aligned_value;
 }
 
+class Defer {
+public:
+	Defer(std::function<void()> func) :
+			func_(func) {}
+	~Defer() { func_(); }
+
+private:
+	std::function<void()> func_;
+};
+
+#define CONCAT_INTERNAL(x, y) x##y
+#define CONCAT(x, y) CONCAT_INTERNAL(x, y)
+#define DEFER const Defer &CONCAT(defer__, __LINE__) = Defer
+
+extern os_log_t LOG_DRIVER;
+// Used for dynamic tracing.
+extern os_log_t LOG_INTERVALS;
+
 #endif // METAL_UTILS_H

drivers/metal/rendering_device_driver_metal.h

@@ -48,6 +48,8 @@
 class RenderingContextDriverMetal;
 
 class API_AVAILABLE(macos(11.0), ios(14.0)) RenderingDeviceDriverMetal : public RenderingDeviceDriver {
+	friend struct ShaderCacheEntry;
+
 	template <typename T>
 	using Result = std::variant<T, Error>;
 
@@ -77,6 +79,19 @@ class API_AVAILABLE(macos(11.0), ios(14.0)) RenderingDeviceDriverMetal : public
 	Error _create_device();
 	Error _check_capabilities();
 
+#pragma mark - Shader Cache
+
+	ShaderLoadStrategy _shader_load_strategy = ShaderLoadStrategy::DEFAULT;
+
+	/**
+	 * The shader cache is a map of hashes of the Metal source to shader cache entries.
+	 *
+	 * To prevent unbounded growth of the cache, cache entries are automatically freed when
+	 * there are no more references to the MDLibrary associated with the cache entry.
+	 */
+	HashMap<SHA256Digest, ShaderCacheEntry *, HashableHasher<SHA256Digest>> _shader_cache;
+	void shader_cache_free_entry(const SHA256Digest &key);
+
 public:
 	Error initialize(uint32_t p_device_index, uint32_t p_frame_count) override final;
 
@@ -270,7 +285,7 @@ public:
 #pragma mark Pipeline
 
 private:
-	Result<id<MTLFunction>> _create_function(id<MTLLibrary> p_library, NSString *p_name, VectorView<PipelineSpecializationConstant> &p_specialization_constants);
+	Result<id<MTLFunction>> _create_function(MDLibrary *p_library, NSString *p_name, VectorView<PipelineSpecializationConstant> &p_specialization_constants);
 
 public:
 	virtual void pipeline_free(PipelineID p_pipeline_id) override final;

drivers/metal/rendering_device_driver_metal.mm

@@ -60,9 +60,22 @@
 
 #import <Metal/MTLTexture.h>
 #import <Metal/Metal.h>
+#import <os/log.h>
+#import <os/signpost.h>
 #import <spirv_msl.hpp>
 #import <spirv_parser.hpp>
 
+#pragma mark - Logging
+
+os_log_t LOG_DRIVER;
+// Used for dynamic tracing.
+os_log_t LOG_INTERVALS;
+
+__attribute__((constructor)) static void InitializeLogging(void) {
+	LOG_DRIVER = os_log_create("org.stuartcarnie.godot.metal", OS_LOG_CATEGORY_POINTS_OF_INTEREST);
+	LOG_INTERVALS = os_log_create("org.stuartcarnie.godot.metal", "events");
+}
+
 /*****************/
 /**** GENERIC ****/
 /*****************/
@@ -2258,6 +2271,15 @@ Vector<uint8_t> RenderingDeviceDriverMetal::shader_compile_binary_from_spirv(Vec
 	return ret;
 }
 
+void RenderingDeviceDriverMetal::shader_cache_free_entry(const SHA256Digest &key) {
+	if (ShaderCacheEntry **pentry = _shader_cache.getptr(key); pentry != nullptr) {
+		ShaderCacheEntry *entry = *pentry;
+		_shader_cache.erase(key);
+		entry->library = nil;
+		memdelete(entry);
+	}
+}
+
 RDD::ShaderID RenderingDeviceDriverMetal::shader_create_from_bytecode(const Vector<uint8_t> &p_shader_binary, ShaderDescription &r_shader_desc, String &r_name) {
 	r_shader_desc = {}; // Driver-agnostic.
 
@@ -2285,18 +2307,32 @@ RDD::ShaderID RenderingDeviceDriverMetal::shader_create_from_bytecode(const Vect
 
 	MTLCompileOptions *options = [MTLCompileOptions new];
 	options.languageVersion = binary_data.get_msl_version();
-	HashMap<ShaderStage, id<MTLLibrary>> libraries;
+	HashMap<ShaderStage, MDLibrary *> libraries;
+
 	for (ShaderStageData &shader_data : binary_data.stages) {
-		NSString *source = [[NSString alloc] initWithBytesNoCopy:(void *)shader_data.source.ptr()
-														  length:shader_data.source.length()
-														encoding:NSUTF8StringEncoding
-													freeWhenDone:NO];
-		NSError *error = nil;
-		id<MTLLibrary> library = [device newLibraryWithSource:source options:options error:&error];
-		if (error != nil) {
-			print_error(error.localizedDescription.UTF8String);
-			ERR_FAIL_V_MSG(ShaderID(), "failed to compile Metal source");
+		SHA256Digest key = SHA256Digest(shader_data.source.ptr(), shader_data.source.length());
+
+		if (ShaderCacheEntry **p = _shader_cache.getptr(key); p != nullptr) {
+			libraries[shader_data.stage] = (*p)->library;
+			continue;
 		}
+
+		NSString *source = [[NSString alloc] initWithBytes:(void *)shader_data.source.ptr()
+													length:shader_data.source.length()
+												  encoding:NSUTF8StringEncoding];
+
+		ShaderCacheEntry *cd = memnew(ShaderCacheEntry(*this, key));
+		cd->name = binary_data.shader_name;
+		String sha_hex = String::hex_encode_buffer(key.data, CC_SHA256_DIGEST_LENGTH);
+		cd->short_sha = sha_hex.substr(0, 8).utf8();
+		cd->stage = shader_data.stage;
+
+		MDLibrary *library = [MDLibrary newLibraryWithCacheEntry:cd
+														  device:device
+														  source:source
+														 options:options
+														strategy:_shader_load_strategy];
+		_shader_cache[key] = cd;
 		libraries[shader_data.stage] = library;
 	}
 
@@ -3062,8 +3098,13 @@ void RenderingDeviceDriverMetal::command_render_set_line_width(CommandBufferID p
 
 // ----- PIPELINE -----
 
-RenderingDeviceDriverMetal::Result<id<MTLFunction>> RenderingDeviceDriverMetal::_create_function(id<MTLLibrary> p_library, NSString *p_name, VectorView<PipelineSpecializationConstant> &p_specialization_constants) {
-	id<MTLFunction> function = [p_library newFunctionWithName:p_name];
+RenderingDeviceDriverMetal::Result<id<MTLFunction>> RenderingDeviceDriverMetal::_create_function(MDLibrary *p_library, NSString *p_name, VectorView<PipelineSpecializationConstant> &p_specialization_constants) {
+	id<MTLLibrary> library = p_library.library;
+	if (!library) {
+		ERR_FAIL_V_MSG(ERR_CANT_CREATE, "Failed to compile Metal library");
+	}
+
+	id<MTLFunction> function = [library newFunctionWithName:p_name];
 	ERR_FAIL_NULL_V_MSG(function, ERR_CANT_CREATE, "No function named main0");
 
 	if (function.functionConstantsDictionary.count == 0) {
@@ -3141,9 +3182,9 @@ RenderingDeviceDriverMetal::Result<id<MTLFunction>> RenderingDeviceDriverMetal::
 	}
 
 	NSError *err = nil;
-	function = [p_library newFunctionWithName:@"main0"
-							   constantValues:constantValues
-										error:&err];
+	function = [library newFunctionWithName:@"main0"
+							 constantValues:constantValues
+									  error:&err];
 	ERR_FAIL_NULL_V_MSG(function, ERR_CANT_CREATE, String("specialized function failed: ") + err.localizedDescription.UTF8String);
 
 	return function;
@@ -3188,6 +3229,14 @@ RDD::PipelineID RenderingDeviceDriverMetal::render_pipeline_create(
 	MTLVertexDescriptor *vert_desc = rid::get(p_vertex_format);
 	MDRenderPass *pass = (MDRenderPass *)(p_render_pass.id);
 
+	os_signpost_id_t reflect_id = os_signpost_id_make_with_pointer(LOG_INTERVALS, shader);
+	os_signpost_interval_begin(LOG_INTERVALS, reflect_id, "render_pipeline_create", "shader_name=%{public}s", shader->name.get_data());
+	DEFER([=]() {
+		os_signpost_interval_end(LOG_INTERVALS, reflect_id, "render_pipeline_create");
+	});
+
+	os_signpost_event_emit(LOG_DRIVER, OS_SIGNPOST_ID_EXCLUSIVE, "create_pipeline");
+
 	MTLRenderPipelineDescriptor *desc = [MTLRenderPipelineDescriptor new];
 
 	{
@@ -3482,9 +3531,15 @@ void RenderingDeviceDriverMetal::command_compute_dispatch_indirect(CommandBuffer
 RDD::PipelineID RenderingDeviceDriverMetal::compute_pipeline_create(ShaderID p_shader, VectorView<PipelineSpecializationConstant> p_specialization_constants) {
 	MDComputeShader *shader = (MDComputeShader *)(p_shader.id);
 
-	id<MTLLibrary> library = shader->kernel;
+	os_signpost_id_t reflect_id = os_signpost_id_make_with_pointer(LOG_INTERVALS, shader);
+	os_signpost_interval_begin(LOG_INTERVALS, reflect_id, "compute_pipeline_create", "shader_name=%{public}s", shader->name.get_data());
+	DEFER([=]() {
+		os_signpost_interval_end(LOG_INTERVALS, reflect_id, "compute_pipeline_create");
+	});
 
-	Result<id<MTLFunction>> function_or_err = _create_function(library, @"main0", p_specialization_constants);
+	os_signpost_event_emit(LOG_DRIVER, OS_SIGNPOST_ID_EXCLUSIVE, "create_pipeline");
+
+	Result<id<MTLFunction>> function_or_err = _create_function(shader->kernel, @"main0", p_specialization_constants);
 	ERR_FAIL_COND_V(std::holds_alternative<Error>(function_or_err), PipelineID());
 	id<MTLFunction> function = std::get<id<MTLFunction>>(function_or_err);
 
@@ -3585,12 +3640,13 @@ void RenderingDeviceDriverMetal::set_object_name(ObjectType p_type, ID p_driver_
 			buffer.label = [NSString stringWithUTF8String:p_name.utf8().get_data()];
 		} break;
 		case OBJECT_TYPE_SHADER: {
+			NSString *label = [NSString stringWithUTF8String:p_name.utf8().get_data()];
 			MDShader *shader = (MDShader *)(p_driver_id.id);
 			if (MDRenderShader *rs = dynamic_cast<MDRenderShader *>(shader); rs != nullptr) {
-				rs->vert.label = [NSString stringWithUTF8String:p_name.utf8().get_data()];
-				rs->frag.label = [NSString stringWithUTF8String:p_name.utf8().get_data()];
+				[rs->vert setLabel:label];
+				[rs->frag setLabel:label];
 			} else if (MDComputeShader *cs = dynamic_cast<MDComputeShader *>(shader); cs != nullptr) {
-				cs->kernel.label = [NSString stringWithUTF8String:p_name.utf8().get_data()];
+				[cs->kernel setLabel:label];
 			} else {
 				DEV_ASSERT(false);
 			}
@@ -3830,12 +3886,20 @@ size_t RenderingDeviceDriverMetal::get_texel_buffer_alignment_for_format(MTLPixe
 RenderingDeviceDriverMetal::RenderingDeviceDriverMetal(RenderingContextDriverMetal *p_context_driver) :
 		context_driver(p_context_driver) {
 	DEV_ASSERT(p_context_driver != nullptr);
+
+	if (String res = OS::get_singleton()->get_environment("GODOT_MTL_SHADER_LOAD_STRATEGY"); res == U"lazy") {
+		_shader_load_strategy = ShaderLoadStrategy::LAZY;
+	}
 }
 
 RenderingDeviceDriverMetal::~RenderingDeviceDriverMetal() {
 	for (MDCommandBuffer *cb : command_buffers) {
 		delete cb;
 	}
+
+	for (KeyValue<SHA256Digest, ShaderCacheEntry *> &kv : _shader_cache) {
+		memdelete(kv.value);
+	}
 }
 
 #pragma mark - Initialization