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[Fix] (MG_Util, MG_Backend/DirectVulkan): GL reads gl_BaseVertex as zero on a non-indexed draw where Vulkan's builtin hands over firstVertex

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swung0x48
2026-08-12 04:18:07 -04:00
parent 7625cf450d
commit 7311251f30
9 changed files with 318 additions and 2 deletions
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MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp
+34 -1
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@@ -5821,7 +5821,40 @@ void main() {
m_lastLodParamsSum = 0; // filled below once the sampled set is known
}
}
const auto& programObj = m_programFactory->GetOrCreateProgram(program, transformFlags);
// GL's gl_BaseVertex is zero for every command without a baseVertex parameter, while
// Vulkan's builtin reports the draw's firstVertex; a non-indexed draw therefore takes
// the zeroed program variant. The question is about the program's SPIR-V, not about
// this draw, so it is memoized on (program lifetime, backend-state version): only the
// very first draw of a program pays the extra lookup, and a program used exclusively
// with non-indexed draws never resolves - never compiles, never re-stamps - the
// variant no draw of it would use.
const Bool nonIndexedDraw = !(aspects & DrawSetupAspect::IndexBuffer);
const Uint64 baseVertexProgramLifetimeId = program.GetLifetimeId();
const Uint32 baseVertexProgramVersion = program.GetBackendStateVersion();
const Bool baseVertexQueryKnown = m_lastBaseVertexQueryValid &&
m_lastBaseVertexProgramLifetimeId == baseVertexProgramLifetimeId &&
m_lastBaseVertexProgramVersion == baseVertexProgramVersion;
if (baseVertexQueryKnown && nonIndexedDraw && m_lastBaseVertexReads) {
transformFlags |= ProgramFactory::CompileOptionBit::ZeroBaseVertex;
}
const ProgramFactory::VkProgramObject* resolvedProgramObj =
&m_programFactory->GetOrCreateProgram(program, transformFlags);
if (!baseVertexQueryKnown) {
// Read the answer out of the entry BEFORE any second lookup: that lookup may
// insert and move every entry of the open-addressing cache, dangling the
// reference. The zeroing pass leaves the variable declared, so the variant just
// resolved answers the same as the base one either way.
const Bool readsBaseVertex = resolvedProgramObj->readsBaseVertexBuiltin;
m_lastBaseVertexQueryValid = true;
m_lastBaseVertexProgramLifetimeId = baseVertexProgramLifetimeId;
m_lastBaseVertexProgramVersion = baseVertexProgramVersion;
m_lastBaseVertexReads = readsBaseVertex;
if (nonIndexedDraw && readsBaseVertex) {
transformFlags |= ProgramFactory::CompileOptionBit::ZeroBaseVertex;
resolvedProgramObj = &m_programFactory->GetOrCreateProgram(program, transformFlags);
}
}
const auto& programObj = *resolvedProgramObj;
// For the snapshot's memoised entry pointer: if anything below inserts into the
// program cache (blit/aux program compiles), the epoch moves and the snapshot
// stores no pointer for this draw - the fast path then re-looks-up once.