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Program 203 reuses prefixSumCache for a second subgroup reduction before every workgroup invocation has consumed the first result. Add a fingerprint-gated SPIR-V pass that inserts the missing Workgroup acquire-release barrier while preserving native subgroup operations. Keep the repair opt-in behind MOBILEGL_ITERATIONRP_FIX_BARRIER, cover insertion, pass-through, and idempotence, and enable it together with the existing iterationRP subgroup repairs for the matching Linux and Android CI retraces.
64 lines
3.3 KiB
C++
64 lines
3.3 KiB
C++
// MobileGL - MobileGL/MG_Backend/DirectVulkan/SubgroupSupportPolicy.h
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// Copyright (c) 2026 MobileGL-Dev
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// Licensed under the GNU Lesser General Public License v3.0:
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// https://www.gnu.org/licenses/gpl-3.0.txt
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// https://www.gnu.org/licenses/lgpl-3.0.txt
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// SPDX-License-Identifier: LGPL-3.0-only
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// End of Source File Header
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#pragma once
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#include <Config.h>
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#include <Includes.h>
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namespace MobileGL::MG_Backend::DirectVulkan {
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// The single decision point for how DirectVulkan implements GL_KHR_shader_subgroup,
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// shared by capability advertisement (BackendObject) and module lowering
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// (VulkanRenderer / ProgramFactory) so the two can never disagree.
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//
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// Native subgroups are the implementation whenever the device has them, whatever
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// their width - subgroup operations execute on the hardware paths they were made
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// for. Module-level repairs keep the GL contract intact around them:
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// - FixIterationRPSubgroupScratchPass patches the one known pack bug: iterationRP's
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// prefixSumCache[32], under-declared for sub-16-lane devices (8-lane lavapipe);
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// - FixIterationRPBarrierPass repairs Program 203's race between two reductions
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// reusing that scratch, when explicitly enabled;
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// - DeriveNumSubgroupsPass replaces the one builtin drivers get wrong
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// (gl_NumSubgroups) with the value the rest of the topology implies.
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// The 32-lane shared-memory emulation (EmulateSubgroupsPass) is a LAST RESORT for
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// devices with no subgroup support at all, and only when the user opts in with
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// MOBILEGL_MAGMA_EMULATE_SUBGROUP=1; it never replaces available native operations.
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inline constexpr Uint32 kEmulatedSubgroupSize = 32u;
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inline constexpr Uint32 kEmulatedSubgroupStages = GL_COMPUTE_SHADER_BIT;
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inline constexpr Uint32 kEmulatedSubgroupFeatures =
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GL_SUBGROUP_FEATURE_BASIC_BIT_KHR | GL_SUBGROUP_FEATURE_VOTE_BIT_KHR |
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GL_SUBGROUP_FEATURE_ARITHMETIC_BIT_KHR | GL_SUBGROUP_FEATURE_BALLOT_BIT_KHR |
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GL_SUBGROUP_FEATURE_SHUFFLE_BIT_KHR | GL_SUBGROUP_FEATURE_SHUFFLE_RELATIVE_BIT_KHR |
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GL_SUBGROUP_FEATURE_CLUSTERED_BIT_KHR | GL_SUBGROUP_FEATURE_QUAD_BIT_KHR;
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inline Bool ShouldEmulateSubgroups(const Bool nativeSubgroupSupported) {
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return MG_Config::Features.MagmaEmulateSubgroup && !nativeSubgroupSupported &&
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!MG_Config::Features.DisableSubgroup;
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}
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inline Bool ShouldFixIterationRPSubgroupScratch() {
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// Auto is ON: the patch is fingerprint-gated to iterationRP's reduction and
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// grows one under-declared array; every other module passes through untouched.
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return MG_Config::Features.FixIterationRPSubgroupScratch !=
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MG_Config::QuirkOverride::ForceOff;
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}
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inline Bool ShouldFixIterationRPBarrier() {
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return MG_Config::Features.IterationRPFixBarrier;
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}
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inline Bool ShouldDeriveNumSubgroups() {
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// Auto is ON: gl_NumSubgroups must agree with the gl_SubgroupID range for the GL
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// contract to hold, and the derived ceil() value is the one the renderer can pin
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// with REQUIRE_FULL_SUBGROUPS - the driver builtin is the value with no
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// cross-driver guarantee (Adreno returns 1 for an 8-subgroup dispatch).
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return MG_Config::Features.DeriveNumSubgroups != MG_Config::QuirkOverride::ForceOff;
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}
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} // namespace MobileGL::MG_Backend::DirectVulkan
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