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[Refactor] (ShaderTranspiler, DirectVulkan): replace the hand-rolled SPIR-V word walkers with a DecoratePositionInvariantPass and SPIRV-Reflect-based InstanceIndex detection

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This commit is contained in:
swung0x48
2026-07-20 08:35:00 -04:00
parent c81dd04f08
commit 65ea54da9e
10 changed files with 543 additions and 111 deletions
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MobileGL/MG_Backend/DirectVulkan/Renderer/ProgramFactory.cpp
+47 -48
View File
@@ -312,34 +312,6 @@ namespace MobileGL::MG_Backend::DirectVulkan {
return targetEnv;
}
// Cheap raw-word scan for an `OpDecorate <id> BuiltIn InstanceIndex` decoration. Used
// only to decide whether to warn when shaderDrawParameters is unavailable; a false
// negative merely suppresses a diagnostic.
Bool SpirvDeclaresInstanceIndexBuiltin(const Vector<Uint>& spirv) {
constexpr Uint32 kSpirvMagicNumber = 0x07230203u;
constexpr SizeT kHeaderWordCount = 5;
if (spirv.size() <= kHeaderWordCount || spirv[0] != kSpirvMagicNumber) {
return false;
}
SizeT wordIndex = kHeaderWordCount;
while (wordIndex < spirv.size()) {
const Uint32 firstWord = spirv[wordIndex];
const Uint32 wordCount = firstWord >> 16;
const auto opcode = static_cast<spv::Op>(firstWord & 0xffffu);
if (wordCount == 0 || wordIndex + wordCount > spirv.size()) {
break;
}
if (opcode == spv::Op::OpDecorate && wordCount >= 4 &&
static_cast<spv::Decoration>(spirv[wordIndex + 2]) == spv::Decoration::BuiltIn &&
static_cast<spv::BuiltIn>(spirv[wordIndex + 3]) == spv::BuiltIn::InstanceIndex) {
return true;
}
wordIndex += wordCount;
}
return false;
}
Bool IsInterfaceVariableStaticallyUsed(const Vector<Uint>& spirv, Uint32 spirvId) {
if (spirv.empty() || spirvId == 0) {
return false;
@@ -1234,6 +1206,25 @@ namespace MobileGL::MG_Backend::DirectVulkan {
return false;
}
// glslang's relaxed-Vulkan mode maps GL's gl_InstanceID onto the InstanceIndex builtin.
// Without shaderDrawParameters there is no gl_BaseInstance to subtract, so such a shader
// cannot be corrected and instanced draws with a non-zero baseInstance misrender; this
// detects the case so the user gets one warning instead of silent corruption.
Bool ProgramFactory::ReflectedReadsInstanceIndexBuiltin(const SpvReflectShaderModule& reflectModule) {
for (Uint32 entryIndex = 0; entryIndex < reflectModule.entry_point_count; ++entryIndex) {
const SpvReflectEntryPoint& entryPoint = reflectModule.entry_points[entryIndex];
for (Uint32 variableIndex = 0; variableIndex < entryPoint.input_variable_count; ++variableIndex) {
const SpvReflectInterfaceVariable* variable = entryPoint.input_variables[variableIndex];
if (variable != nullptr &&
(variable->decoration_flags & SPV_REFLECT_DECORATION_BUILT_IN) != 0 &&
variable->built_in == SpvBuiltInInstanceIndex) {
return true;
}
}
}
return false;
}
VkShaderStageFlagBits ProgramFactory::ToVkStage(ShaderStage stage) {
switch (stage) {
case ShaderStage::Vertex:
@@ -1481,6 +1472,15 @@ namespace MobileGL::MG_Backend::DirectVulkan {
continue;
}
if (!m_shaderDrawParametersEnabled && ReflectedReadsInstanceIndexBuiltin(reflectModule)) {
static Bool s_warnedInstanceIndexUnsupported = false;
if (!s_warnedInstanceIndexUnsupported) {
s_warnedInstanceIndexUnsupported = true;
MGLOG_W("ProgramFactory: shaderDrawParameters is unavailable; gl_InstanceID cannot be "
"rebased and instanced draws with a non-zero baseInstance may render incorrectly");
}
}
uint32_t inputCount = 0;
SpvReflectResult reflectResult = spvReflectEnumerateInputVariables(&reflectModule, &inputCount, nullptr);
MOBILEGL_ASSERT(reflectResult == SPV_REFLECT_RESULT_SUCCESS,
@@ -1892,8 +1892,12 @@ namespace MobileGL::MG_Backend::DirectVulkan {
moduleSpirvs[i], invariantSpirv)) {
moduleSpirvs[i] = std::move(invariantSpirv);
} else {
MGLOG_W("ProgramFactory: position-invariant decoration failed for program %u; "
"keeping the original module",
// The pass round-trips through SPIRV-Tools IR, so an unparseable module
// fails open and keeps the undecorated words - which silently reinstates
// the multi-pass invariance bug rather than breaking anything loudly.
MGLOG_E("ProgramFactory: position-invariant decoration failed for program %u; "
"keeping the original module - multi-pass depth-equality chains "
"(e.g. MC 26.3 OIT clouds) may drop primitives on this device",
program.GetExternalIndex());
}
}
@@ -1902,24 +1906,19 @@ namespace MobileGL::MG_Backend::DirectVulkan {
// gl_InstanceIndex, which wrongly includes the draw's baseInstance. Rebase vertex-stage
// loads to (InstanceIndex - BaseInstance) so shaders observe GL semantics. Reflection
// below runs on the rebased words so the added BaseInstance builtin stays consistent.
if (shaders[i] && shaders[i]->GetShaderStage() == ShaderStage::Vertex) {
if (m_shaderDrawParametersEnabled) {
Vector<Uint> rebasedSpirv;
if (MG_Util::ShaderTranspiler::ShaderCompiler::RebaseInstanceIndexForVulkan(moduleSpirvs[i],
rebasedSpirv)) {
moduleSpirvs[i] = std::move(rebasedSpirv);
} else {
MGLOG_E("ProgramFactory: failed to rebase gl_InstanceID for program %u; "
"instanced draws with a non-zero baseInstance may render incorrectly",
program.GetExternalIndex());
}
} else if (SpirvDeclaresInstanceIndexBuiltin(moduleSpirvs[i])) {
static Bool s_warnedInstanceIndexUnsupported = false;
if (!s_warnedInstanceIndexUnsupported) {
s_warnedInstanceIndexUnsupported = true;
MGLOG_W("ProgramFactory: shaderDrawParameters is unavailable; gl_InstanceID cannot be "
"rebased and instanced draws with a non-zero baseInstance may render incorrectly");
}
// The unsupported-device counterpart of this rebase (warning when a shader reads
// the builtin but shaderDrawParameters is missing) rides along with
// ReflectVertexInputs, which already reflects this stage.
if (shaders[i] && shaders[i]->GetShaderStage() == ShaderStage::Vertex &&
m_shaderDrawParametersEnabled) {
Vector<Uint> rebasedSpirv;
if (MG_Util::ShaderTranspiler::ShaderCompiler::RebaseInstanceIndexForVulkan(moduleSpirvs[i],
rebasedSpirv)) {
moduleSpirvs[i] = std::move(rebasedSpirv);
} else {
MGLOG_E("ProgramFactory: failed to rebase gl_InstanceID for program %u; "
"instanced draws with a non-zero baseInstance may render incorrectly",
program.GetExternalIndex());
}
}
MobileGL/MG_Backend/DirectVulkan/Renderer/ProgramFactory.h
+3
View File
@@ -223,6 +223,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
// can be pinned by tests. A false negative loses the exemption, so such a shader is
// stripped conservatively and forfeits its depth write.
static Bool ReflectedFragmentReplacesDepth(const SpvReflectShaderModule& reflectModule);
// True when an entry point reads the InstanceIndex builtin. Only gates a diagnostic:
// without shaderDrawParameters such a shader cannot have gl_InstanceID rebased.
static Bool ReflectedReadsInstanceIndexBuiltin(const SpvReflectShaderModule& reflectModule);
private:
struct ProgramLookupCache {