#include "stdafx.h"
#include "GLGSRender.h"
#include "../rsx_methods.h"
#include "../Common/BufferUtils.h"

namespace gl
{
	GLenum comparison_op(rsx::comparison_function op)
	{
		switch (op)
		{
		case rsx::comparison_function::never: return GL_NEVER;
		case rsx::comparison_function::less: return GL_LESS;
		case rsx::comparison_function::equal: return GL_EQUAL;
		case rsx::comparison_function::less_or_equal: return GL_LEQUAL;
		case rsx::comparison_function::greater: return GL_GREATER;
		case rsx::comparison_function::not_equal: return GL_NOTEQUAL;
		case rsx::comparison_function::greater_or_equal: return GL_GEQUAL;
		case rsx::comparison_function::always: return GL_ALWAYS;
		}
		fmt::throw_exception("Unsupported comparison op 0x%X", static_cast<u32>(op));
	}

	GLenum stencil_op(rsx::stencil_op op)
	{
		switch (op)
		{
		case rsx::stencil_op::invert: return GL_INVERT;
		case rsx::stencil_op::keep: return GL_KEEP;
		case rsx::stencil_op::zero: return GL_ZERO;
		case rsx::stencil_op::replace: return GL_REPLACE;
		case rsx::stencil_op::incr: return GL_INCR;
		case rsx::stencil_op::decr: return GL_DECR;
		case rsx::stencil_op::incr_wrap: return GL_INCR_WRAP;
		case rsx::stencil_op::decr_wrap: return GL_DECR_WRAP;
		}
		fmt::throw_exception("Unsupported stencil op 0x%X", static_cast<u32>(op));
	}

	GLenum blend_equation(rsx::blend_equation op)
	{
		switch (op)
		{
			// Note : maybe add is signed on gl
		case rsx::blend_equation::add_signed:
			rsx_log.trace("blend equation add_signed used. Emulating using FUNC_ADD");
			[[fallthrough]];
		case rsx::blend_equation::add: return GL_FUNC_ADD;
		case rsx::blend_equation::min: return GL_MIN;
		case rsx::blend_equation::max: return GL_MAX;
		case rsx::blend_equation::subtract: return GL_FUNC_SUBTRACT;
		case rsx::blend_equation::reverse_subtract_signed:
			rsx_log.trace("blend equation reverse_subtract_signed used. Emulating using FUNC_REVERSE_SUBTRACT");
			[[fallthrough]];
		case rsx::blend_equation::reverse_subtract: return GL_FUNC_REVERSE_SUBTRACT;
		case rsx::blend_equation::reverse_add_signed:
		default:
			rsx_log.error("Blend equation 0x%X is unimplemented!", static_cast<u32>(op));
			return GL_FUNC_ADD;
		}
	}

	GLenum blend_factor(rsx::blend_factor op)
	{
		switch (op)
		{
		case rsx::blend_factor::zero: return GL_ZERO;
		case rsx::blend_factor::one: return GL_ONE;
		case rsx::blend_factor::src_color: return GL_SRC_COLOR;
		case rsx::blend_factor::one_minus_src_color: return GL_ONE_MINUS_SRC_COLOR;
		case rsx::blend_factor::dst_color: return GL_DST_COLOR;
		case rsx::blend_factor::one_minus_dst_color: return GL_ONE_MINUS_DST_COLOR;
		case rsx::blend_factor::src_alpha: return GL_SRC_ALPHA;
		case rsx::blend_factor::one_minus_src_alpha: return GL_ONE_MINUS_SRC_ALPHA;
		case rsx::blend_factor::dst_alpha: return GL_DST_ALPHA;
		case rsx::blend_factor::one_minus_dst_alpha: return GL_ONE_MINUS_DST_ALPHA;
		case rsx::blend_factor::src_alpha_saturate: return GL_SRC_ALPHA_SATURATE;
		case rsx::blend_factor::constant_color: return GL_CONSTANT_COLOR;
		case rsx::blend_factor::one_minus_constant_color: return GL_ONE_MINUS_CONSTANT_COLOR;
		case rsx::blend_factor::constant_alpha: return GL_CONSTANT_ALPHA;
		case rsx::blend_factor::one_minus_constant_alpha: return GL_ONE_MINUS_CONSTANT_ALPHA;
		}
		fmt::throw_exception("Unsupported blend factor 0x%X", static_cast<u32>(op));
	}

	GLenum logic_op(rsx::logic_op op)
	{
		switch (op)
		{
		case rsx::logic_op::logic_clear: return GL_CLEAR;
		case rsx::logic_op::logic_and: return GL_AND;
		case rsx::logic_op::logic_and_reverse: return GL_AND_REVERSE;
		case rsx::logic_op::logic_copy: return GL_COPY;
		case rsx::logic_op::logic_and_inverted: return GL_AND_INVERTED;
		case rsx::logic_op::logic_noop: return GL_NOOP;
		case rsx::logic_op::logic_xor: return GL_XOR;
		case rsx::logic_op::logic_or: return GL_OR;
		case rsx::logic_op::logic_nor: return GL_NOR;
		case rsx::logic_op::logic_equiv: return GL_EQUIV;
		case rsx::logic_op::logic_invert: return GL_INVERT;
		case rsx::logic_op::logic_or_reverse: return GL_OR_REVERSE;
		case rsx::logic_op::logic_copy_inverted: return GL_COPY_INVERTED;
		case rsx::logic_op::logic_or_inverted: return GL_OR_INVERTED;
		case rsx::logic_op::logic_nand: return GL_NAND;
		case rsx::logic_op::logic_set: return GL_SET;
		}
		fmt::throw_exception("Unsupported logic op 0x%X", static_cast<u32>(op));
	}

	GLenum front_face(rsx::front_face op)
	{
		//NOTE: RSX face winding is always based off of upper-left corner like vulkan, but GL is bottom left
		//shader_window_origin register does not affect this
		//verified with Outrun Online Arcade (window_origin::top) and DS2 (window_origin::bottom)
		//correctness of face winding checked using stencil test (GOW collection shadows)
		switch (op)
		{
		case rsx::front_face::cw: return GL_CCW;
		case rsx::front_face::ccw: return GL_CW;
		}
		fmt::throw_exception("Unsupported front face 0x%X", static_cast<u32>(op));
	}

	GLenum cull_face(rsx::cull_face op)
	{
		switch (op)
		{
		case rsx::cull_face::front: return GL_FRONT;
		case rsx::cull_face::back: return GL_BACK;
		case rsx::cull_face::front_and_back: return GL_FRONT_AND_BACK;
		}
		fmt::throw_exception("Unsupported cull face 0x%X", static_cast<u32>(op));
	}
}

void GLGSRender::update_draw_state()
{
	m_profiler.start();

	gl_state.enable(GL_SCISSOR_TEST);
	gl_state.enable(rsx::method_registers.dither_enabled(), GL_DITHER);

	if (m_rtts.m_bound_depth_stencil.first)
	{
		// Z-buffer is active.
		gl_state.depth_mask(rsx::method_registers.depth_write_enabled());
		gl_state.stencil_mask(rsx::method_registers.stencil_mask());

		gl_state.enable(rsx::method_registers.depth_clamp_enabled() || !rsx::method_registers.depth_clip_enabled(), GL_DEPTH_CLAMP);

		if (gl_state.enable(rsx::method_registers.depth_test_enabled(), GL_DEPTH_TEST))
		{
			gl_state.depth_func(gl::comparison_op(rsx::method_registers.depth_func()));
		}

		if (gl::get_driver_caps().EXT_depth_bounds_test && (gl_state.enable(rsx::method_registers.depth_bounds_test_enabled(), GL_DEPTH_BOUNDS_TEST_EXT)))
		{
			gl_state.depth_bounds(rsx::method_registers.depth_bounds_min(), rsx::method_registers.depth_bounds_max());
		}

		if (gl::get_driver_caps().NV_depth_buffer_float_supported)
		{
			gl_state.depth_range(rsx::method_registers.clip_min(), rsx::method_registers.clip_max());
		}

		if (gl_state.enable(rsx::method_registers.stencil_test_enabled(), GL_STENCIL_TEST))
		{
			gl_state.stencil_func(gl::comparison_op(rsx::method_registers.stencil_func()),
				rsx::method_registers.stencil_func_ref(),
				rsx::method_registers.stencil_func_mask());

			gl_state.stencil_op(gl::stencil_op(rsx::method_registers.stencil_op_fail()), gl::stencil_op(rsx::method_registers.stencil_op_zfail()),
				gl::stencil_op(rsx::method_registers.stencil_op_zpass()));

			if (rsx::method_registers.two_sided_stencil_test_enabled())
			{
				gl_state.stencil_back_mask(rsx::method_registers.back_stencil_mask());

				gl_state.stencil_back_func(gl::comparison_op(rsx::method_registers.back_stencil_func()),
					rsx::method_registers.back_stencil_func_ref(), rsx::method_registers.back_stencil_func_mask());

				gl_state.stencil_back_op(gl::stencil_op(rsx::method_registers.back_stencil_op_fail()),
					gl::stencil_op(rsx::method_registers.back_stencil_op_zfail()), gl::stencil_op(rsx::method_registers.back_stencil_op_zpass()));
			}
		}
	}

	if (m_rtts.get_color_surface_count())
	{
		// Color buffer is active
		for (int index = 0; index < m_rtts.get_color_surface_count(); ++index)
		{
			bool color_mask_b = rsx::method_registers.color_mask_b(index);
			bool color_mask_g = rsx::method_registers.color_mask_g(index);
			bool color_mask_r = rsx::method_registers.color_mask_r(index);
			bool color_mask_a = rsx::method_registers.color_mask_a(index);

			switch (rsx::method_registers.surface_color())
			{
			case rsx::surface_color_format::b8:
				rsx::get_b8_colormask(color_mask_r, color_mask_g, color_mask_b, color_mask_a);
				break;
			case rsx::surface_color_format::g8b8:
				rsx::get_g8b8_r8g8_colormask(color_mask_r, color_mask_g, color_mask_b, color_mask_a);
				break;
			default:
				break;
			}

			gl_state.color_maski(index, color_mask_r, color_mask_g, color_mask_b, color_mask_a);
		}

		// LogicOp and Blend are mutually exclusive. If both are enabled, LogicOp takes precedence.
		// In OpenGL, this behavior is enforced in spec, but let's enforce it at renderer level as well.
		if (gl_state.enable(rsx::method_registers.logic_op_enabled(), GL_COLOR_LOGIC_OP))
		{
			gl_state.logic_op(gl::logic_op(rsx::method_registers.logic_operation()));

			gl_state.enablei(GL_FALSE, GL_BLEND, 0);
			gl_state.enablei(GL_FALSE, GL_BLEND, 1);
			gl_state.enablei(GL_FALSE, GL_BLEND, 2);
			gl_state.enablei(GL_FALSE, GL_BLEND, 3);
		}
		else
		{
			bool mrt_blend_enabled[] =
			{
				rsx::method_registers.blend_enabled(),
				rsx::method_registers.blend_enabled_surface_1(),
				rsx::method_registers.blend_enabled_surface_2(),
				rsx::method_registers.blend_enabled_surface_3()
			};

			if (mrt_blend_enabled[0] || mrt_blend_enabled[1] || mrt_blend_enabled[2] || mrt_blend_enabled[3])
			{
				glBlendFuncSeparate(gl::blend_factor(rsx::method_registers.blend_func_sfactor_rgb()),
					gl::blend_factor(rsx::method_registers.blend_func_dfactor_rgb()),
					gl::blend_factor(rsx::method_registers.blend_func_sfactor_a()),
					gl::blend_factor(rsx::method_registers.blend_func_dfactor_a()));

				auto blend_colors = rsx::get_constant_blend_colors();
				glBlendColor(blend_colors[0], blend_colors[1], blend_colors[2], blend_colors[3]);

				glBlendEquationSeparate(gl::blend_equation(rsx::method_registers.blend_equation_rgb()),
					gl::blend_equation(rsx::method_registers.blend_equation_a()));
			}

			gl_state.enablei(mrt_blend_enabled[0], GL_BLEND, 0);
			gl_state.enablei(mrt_blend_enabled[1], GL_BLEND, 1);
			gl_state.enablei(mrt_blend_enabled[2], GL_BLEND, 2);
			gl_state.enablei(mrt_blend_enabled[3], GL_BLEND, 3);
		}
	}

	switch (rsx::method_registers.current_draw_clause.primitive)
	{
	case rsx::primitive_type::lines:
	case rsx::primitive_type::line_loop:
	case rsx::primitive_type::line_strip:
		gl_state.line_width(rsx::method_registers.line_width() * rsx::get_resolution_scale());
		gl_state.enable(rsx::method_registers.line_smooth_enabled(), GL_LINE_SMOOTH);
		break;
	default:
		gl_state.enable(rsx::method_registers.poly_offset_point_enabled(), GL_POLYGON_OFFSET_POINT);
		gl_state.enable(rsx::method_registers.poly_offset_line_enabled(), GL_POLYGON_OFFSET_LINE);
		gl_state.enable(rsx::method_registers.poly_offset_fill_enabled(), GL_POLYGON_OFFSET_FILL);

		// offset_bias is the constant factor, multiplied by the implementation factor R
		// offset_scale is the slope factor, multiplied by the triangle slope factor M
		const auto poly_offset_scale = rsx::method_registers.poly_offset_scale();
		auto poly_offset_bias = rsx::method_registers.poly_offset_bias();

		if (auto ds = m_rtts.m_bound_depth_stencil.second;
			ds && ds->get_internal_format() == gl::texture::internal_format::depth24_stencil8)
		{
			// Check details in VKDraw.cpp about behaviour of RSX vs desktop D24X8 implementations
			// TLDR, RSX expects R = 16,777,215 (2^24 - 1)
			const auto& caps = gl::get_driver_caps();
			if (caps.vendor_NVIDIA || caps.vendor_MESA)
			{
				// R derived to be 8388607 (2^23 - 1)
				poly_offset_bias *= 0.5f;
			}
			else if (caps.vendor_AMD)
			{
				// R derived to be 4194303 (2^22 - 1)
				poly_offset_bias *= 0.25f;
			}
		}
		gl_state.polygon_offset(poly_offset_scale, poly_offset_bias);

		if (gl_state.enable(rsx::method_registers.cull_face_enabled(), GL_CULL_FACE))
		{
			gl_state.cull_face(gl::cull_face(rsx::method_registers.cull_face_mode()));
		}

		gl_state.front_face(gl::front_face(rsx::method_registers.front_face_mode()));
		break;
	}

	// Clip planes
	gl_state.clip_planes((current_vertex_program.output_mask >> CELL_GCM_ATTRIB_OUTPUT_UC0) & 0x3F);

	// Sample control
	// TODO: MinSampleShading
	//gl_state.enable(rsx::method_registers.msaa_enabled(), GL_MULTISAMPLE);
	//gl_state.enable(rsx::method_registers.msaa_alpha_to_coverage_enabled(), GL_SAMPLE_ALPHA_TO_COVERAGE);
	//gl_state.enable(rsx::method_registers.msaa_alpha_to_one_enabled(), GL_SAMPLE_ALPHA_TO_ONE);

	//TODO
	//NV4097_SET_ANISO_SPREAD
	//NV4097_SET_SPECULAR_ENABLE
	//NV4097_SET_TWO_SIDE_LIGHT_EN
	//NV4097_SET_FLAT_SHADE_OP
	//NV4097_SET_EDGE_FLAG
	//NV4097_SET_COLOR_KEY_COLOR
	//NV4097_SET_SHADER_CONTROL
	//NV4097_SET_ZMIN_MAX_CONTROL
	//NV4097_SET_ANTI_ALIASING_CONTROL
	//NV4097_SET_CLIP_ID_TEST_ENABLE

	// For OGL Z range is updated every draw as it is separate from viewport config
	m_graphics_state.clear(rsx::pipeline_state::zclip_config_state_dirty);

	m_frame_stats.setup_time += m_profiler.duration();
}

void GLGSRender::load_texture_env()
{
	// Load textures
	gl::command_context cmd{ gl_state };
	std::lock_guard lock(m_sampler_mutex);

	for (u32 textures_ref = current_fp_metadata.referenced_textures_mask, i = 0; textures_ref; textures_ref >>= 1, ++i)
	{
		if (!(textures_ref & 1))
			continue;

		if (!fs_sampler_state[i])
			fs_sampler_state[i] = std::make_unique<gl::texture_cache::sampled_image_descriptor>();

		auto sampler_state = static_cast<gl::texture_cache::sampled_image_descriptor*>(fs_sampler_state[i].get());
		const auto& tex = rsx::method_registers.fragment_textures[i];

		if (m_samplers_dirty || m_textures_dirty[i] || m_gl_texture_cache.test_if_descriptor_expired(cmd, m_rtts, sampler_state, tex))
		{
			if (tex.enabled())
			{
				*sampler_state = m_gl_texture_cache.upload_texture(cmd, tex, m_rtts);
			}
			else
			{
				*sampler_state = {};
			}

			if (m_textures_dirty[i] && sampler_state->validate())
			{
				m_fs_sampler_states[i].apply(tex, fs_sampler_state[i].get());
			}

			m_textures_dirty[i] = false;
		}
	}

	for (u32 textures_ref = current_vp_metadata.referenced_textures_mask, i = 0; textures_ref; textures_ref >>= 1, ++i)
	{
		if (!(textures_ref & 1))
			continue;

		if (!vs_sampler_state[i])
			vs_sampler_state[i] = std::make_unique<gl::texture_cache::sampled_image_descriptor>();

		auto sampler_state = static_cast<gl::texture_cache::sampled_image_descriptor*>(vs_sampler_state[i].get());
		const auto& tex = rsx::method_registers.vertex_textures[i];

		if (m_samplers_dirty || m_vertex_textures_dirty[i] || m_gl_texture_cache.test_if_descriptor_expired(cmd, m_rtts, sampler_state, tex))
		{
			if (rsx::method_registers.vertex_textures[i].enabled())
			{
				*sampler_state = m_gl_texture_cache.upload_texture(cmd, rsx::method_registers.vertex_textures[i], m_rtts);
			}
			else
			{
				*sampler_state = {};
			}

			if (m_vertex_textures_dirty[i] && sampler_state->validate())
			{
				m_vs_sampler_states[i].apply(tex, vs_sampler_state[i].get());
			}

			m_vertex_textures_dirty[i] = false;
		}
	}

	m_samplers_dirty.store(false);
}

void GLGSRender::bind_texture_env()
{
	// Bind textures and resolve external copy operations
	gl::command_context cmd{ gl_state };

	for (u32 textures_ref = current_fp_metadata.referenced_textures_mask, i = 0; textures_ref; textures_ref >>= 1, ++i)
	{
		if (!(textures_ref & 1))
			continue;

		gl::texture_view* view = nullptr;
		auto sampler_state = static_cast<gl::texture_cache::sampled_image_descriptor*>(fs_sampler_state[i].get());

		if (rsx::method_registers.fragment_textures[i].enabled() &&
			sampler_state->validate())
		{
			if (view = sampler_state->image_handle; !view) [[unlikely]]
			{
				view = m_gl_texture_cache.create_temporary_subresource(cmd, sampler_state->external_subresource_desc);
			}
		}

		if (view) [[likely]]
		{
			view->bind(cmd, GL_FRAGMENT_TEXTURES_START + i);

			if (current_fragment_program.texture_state.redirected_textures & (1 << i))
			{
				auto root_texture = static_cast<gl::viewable_image*>(view->image());
				auto stencil_view = root_texture->get_view(gl::GL_REMAP_IDENTITY, rsx::default_remap_vector, gl::image_aspect::stencil);
				stencil_view->bind(cmd, GL_STENCIL_MIRRORS_START + i);
			}
		}
		else
		{
			auto target = gl::get_target(current_fragment_program.get_texture_dimension(i));
			cmd->bind_texture(GL_FRAGMENT_TEXTURES_START + i, target, m_null_textures[target]->id());

			if (current_fragment_program.texture_state.redirected_textures & (1 << i))
			{
				cmd->bind_texture(GL_STENCIL_MIRRORS_START + i, target, m_null_textures[target]->id());
			}
		}
	}

	for (u32 textures_ref = current_vp_metadata.referenced_textures_mask, i = 0; textures_ref; textures_ref >>= 1, ++i)
	{
		if (!(textures_ref & 1))
			continue;

		auto sampler_state = static_cast<gl::texture_cache::sampled_image_descriptor*>(vs_sampler_state[i].get());

		if (rsx::method_registers.vertex_textures[i].enabled() &&
			sampler_state->validate())
		{
			if (sampler_state->image_handle) [[likely]]
			{
				sampler_state->image_handle->bind(cmd, GL_VERTEX_TEXTURES_START + i);
			}
			else
			{
				m_gl_texture_cache.create_temporary_subresource(cmd, sampler_state->external_subresource_desc)->bind(cmd, GL_VERTEX_TEXTURES_START + i);
			}
		}
		else
		{
			cmd->bind_texture(GL_VERTEX_TEXTURES_START + i, GL_TEXTURE_2D, GL_NONE);
		}
	}
}

void GLGSRender::emit_geometry(u32 sub_index)
{
	const auto do_heap_cleanup = [this]()
	{
		if (manually_flush_ring_buffers)
		{
			m_attrib_ring_buffer->unmap();
			m_index_ring_buffer->unmap();
		}
		else
		{
			//DMA push; not needed with MAP_COHERENT
			//glMemoryBarrier(GL_CLIENT_MAPPED_BUFFER_BARRIER_BIT);
		}
	};

	m_profiler.start();

	auto& draw_call = rsx::method_registers.current_draw_clause;
	const rsx::flags32_t vertex_state_mask = rsx::vertex_base_changed | rsx::vertex_arrays_changed;
	const rsx::flags32_t vertex_state = (sub_index == 0) ? rsx::vertex_arrays_changed : draw_call.execute_pipeline_dependencies() & vertex_state_mask;

	if (vertex_state & rsx::vertex_arrays_changed)
	{
		analyse_inputs_interleaved(m_vertex_layout);
	}
	else if (vertex_state & rsx::vertex_base_changed)
	{
		// Rebase vertex bases instead of
		for (auto& info : m_vertex_layout.interleaved_blocks)
		{
			const auto vertex_base_offset = rsx::method_registers.vertex_data_base_offset();
			info->real_offset_address = rsx::get_address(rsx::get_vertex_offset_from_base(vertex_base_offset, info->base_offset), info->memory_location);
		}
	}

	if (vertex_state && !m_vertex_layout.validate())
	{
		// No vertex inputs enabled
		// Execute remainining pipeline barriers with NOP draw
		do
		{
			draw_call.execute_pipeline_dependencies();
		} while (draw_call.next());

		draw_call.end();
		return;
	}

	if (manually_flush_ring_buffers)
	{
		//Use approximations to reserve space. This path is mostly for debug purposes anyway
		u32 approx_vertex_count = draw_call.get_elements_count();
		u32 approx_working_buffer_size = approx_vertex_count * 256;

		//Allocate 256K heap if we have no approximation at this time (inlined array)
		m_attrib_ring_buffer->reserve_storage_on_heap(std::max(approx_working_buffer_size, 256 * 1024U));
		m_index_ring_buffer->reserve_storage_on_heap(16 * 1024);
	}

	// Do vertex upload before RTT prep / texture lookups to give the driver time to push data
	auto upload_info = set_vertex_buffer();
	do_heap_cleanup();

	if (upload_info.vertex_draw_count == 0)
	{
		// Malformed vertex setup; abort
		return;
	}

	const GLenum draw_mode = gl::draw_mode(draw_call.primitive);
	update_vertex_env(upload_info);

	m_frame_stats.vertex_upload_time += m_profiler.duration();

	gl_state.use_program(m_program->id());

	if (!upload_info.index_info)
	{
		if (draw_call.is_single_draw())
		{
			glDrawArrays(draw_mode, 0, upload_info.vertex_draw_count);
		}
		else
		{
			const auto subranges = draw_call.get_subranges();
			const auto draw_count = subranges.size();
			const auto driver_caps = gl::get_driver_caps();
			bool use_draw_arrays_fallback = false;

			m_scratch_buffer.resize(draw_count * 24);
			GLint* firsts = reinterpret_cast<GLint*>(m_scratch_buffer.data());
			GLsizei* counts = (firsts + draw_count);
			const GLvoid** offsets = utils::bless<const GLvoid*>(counts + draw_count);

			u32 first = 0;
			u32 dst_index = 0;
			for (const auto &range : subranges)
			{
				firsts[dst_index] = first;
				counts[dst_index] = range.count;
				offsets[dst_index++] = reinterpret_cast<const GLvoid*>(u64{first << 2});

				if (driver_caps.vendor_AMD && (first + range.count) > (0x100000 >> 2))
				{
					//Unlikely, but added here in case the identity buffer is not large enough somehow
					use_draw_arrays_fallback = true;
					break;
				}

				first += range.count;
			}

			if (use_draw_arrays_fallback)
			{
				//MultiDrawArrays is broken on some primitive types using AMD. One known type is GL_TRIANGLE_STRIP but there could be more
				for (u32 n = 0; n < draw_count; ++n)
				{
					glDrawArrays(draw_mode, firsts[n], counts[n]);
				}
			}
			else if (driver_caps.vendor_AMD)
			{
				//Use identity index buffer to fix broken vertexID on AMD
				m_identity_index_buffer->bind();
				glMultiDrawElements(draw_mode, counts, GL_UNSIGNED_INT, offsets, static_cast<GLsizei>(draw_count));
			}
			else
			{
				//Normal render
				glMultiDrawArrays(draw_mode, firsts, counts, static_cast<GLsizei>(draw_count));
			}
		}
	}
	else
	{
		const GLenum index_type = std::get<0>(*upload_info.index_info);
		const u32 index_offset = std::get<1>(*upload_info.index_info);
		const bool restarts_valid = gl::is_primitive_native(draw_call.primitive) && !draw_call.is_disjoint_primitive;

		if (gl_state.enable(restarts_valid && rsx::method_registers.restart_index_enabled(), GL_PRIMITIVE_RESTART))
		{
			glPrimitiveRestartIndex((index_type == GL_UNSIGNED_SHORT) ? 0xffff : 0xffffffff);
		}

		m_index_ring_buffer->bind();

		if (draw_call.is_single_draw())
		{
			glDrawElements(draw_mode, upload_info.vertex_draw_count, index_type, reinterpret_cast<GLvoid*>(u64{index_offset}));
		}
		else
		{
			const auto subranges = draw_call.get_subranges();
			const auto draw_count = subranges.size();
			const u32 type_scale = (index_type == GL_UNSIGNED_SHORT) ? 1 : 2;
			uptr index_ptr = index_offset;
			m_scratch_buffer.resize(draw_count * 16);

			GLsizei *counts = reinterpret_cast<GLsizei*>(m_scratch_buffer.data());
			const GLvoid** offsets = utils::bless<const GLvoid*>(counts + draw_count);
			int dst_index = 0;

			for (const auto &range : subranges)
			{
				const auto index_size = get_index_count(draw_call.primitive, range.count);
				counts[dst_index] = index_size;
				offsets[dst_index++] = reinterpret_cast<const GLvoid*>(index_ptr);

				index_ptr += (index_size << type_scale);
			}

			glMultiDrawElements(draw_mode, counts, index_type, offsets, static_cast<GLsizei>(draw_count));
		}
	}

	m_frame_stats.draw_exec_time += m_profiler.duration();
}

void GLGSRender::begin()
{
	// Save shader state now before prefetch and loading happens
	m_interpreter_state = (m_graphics_state & rsx::pipeline_state::invalidate_pipeline_bits);

	rsx::thread::begin();

	if (skip_current_frame || cond_render_ctrl.disable_rendering())
	{
		return;
	}

	init_buffers(rsx::framebuffer_creation_context::context_draw);

	if (m_graphics_state & rsx::pipeline_state::invalidate_pipeline_bits)
	{
		// Shaders need to be reloaded.
		m_program = nullptr;
	}
}

void GLGSRender::end()
{
	m_profiler.start();

	if (skip_current_frame || !m_graphics_state.test(rsx::rtt_config_valid) || cond_render_ctrl.disable_rendering())
	{
		execute_nop_draw();
		rsx::thread::end();
		return;
	}

	if (m_graphics_state & (rsx::pipeline_state::fragment_program_ucode_dirty | rsx::pipeline_state::vertex_program_ucode_dirty))
	{
		analyse_current_rsx_pipeline();
	}

	m_frame_stats.setup_time += m_profiler.duration();

	// Active texture environment is used to decode shaders
	load_texture_env();
	m_frame_stats.textures_upload_time += m_profiler.duration();

	// NOTE: Due to common OpenGL driver architecture, vertex data has to be uploaded as far away from the draw as possible
	// TODO: Implement shaders cache prediction to avoid uploading vertex data if draw is going to skip
	if (!load_program())
	{
		// Program is not ready, skip drawing this
		std::this_thread::yield();
		execute_nop_draw();
		// m_rtts.on_write(); - breaks games for obvious reasons
		rsx::thread::end();
		return;
	}

	// Load program execution environment
	load_program_env();
	m_frame_stats.setup_time += m_profiler.duration();

	bind_texture_env();
	m_gl_texture_cache.release_uncached_temporary_subresources();
	m_frame_stats.textures_upload_time += m_profiler.duration();

	gl::command_context cmd{ gl_state };
	if (auto ds = std::get<1>(m_rtts.m_bound_depth_stencil)) ds->write_barrier(cmd);

	for (auto &rtt : m_rtts.m_bound_render_targets)
	{
		if (auto surface = std::get<1>(rtt))
		{
			surface->write_barrier(cmd);
		}
	}

	update_draw_state();

	if (g_cfg.video.debug_output)
	{
		m_program->validate();
	}

	rsx::method_registers.current_draw_clause.begin();
	u32 subdraw = 0u;
	do
	{
		emit_geometry(subdraw++);
	}
	while (rsx::method_registers.current_draw_clause.next());

	m_rtts.on_write(m_framebuffer_layout.color_write_enabled, m_framebuffer_layout.zeta_write_enabled);

	m_attrib_ring_buffer->notify();
	m_index_ring_buffer->notify();
	m_fragment_env_buffer->notify();
	m_vertex_env_buffer->notify();
	m_texture_parameters_buffer->notify();
	m_vertex_layout_buffer->notify();
	m_fragment_constants_buffer->notify();
	m_transform_constants_buffer->notify();

	m_frame_stats.setup_time += m_profiler.duration();

	rsx::thread::end();
}
