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[Feat] (MG_Util/ShaderTranspiler, MG_Backend, MG_Util/SelfTest): emulate gl_ClipDistance where the backend cannot clip natively and report it in POST

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This commit is contained in:
swung0x48
2026-11-07 02:06:25 -04:00
parent d3ec9b8179
commit 6182704c03
35 changed files with 2050 additions and 46 deletions
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MobileGL/MG_State/GLState/ProgramState/ProgramSpirvTask.cpp
+52 -2
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@@ -33,6 +33,12 @@ namespace MobileGL::MG_State::GLState {
}
std::atomic_flag g_pointSizeDeclineReported;
std::atomic_flag g_pointSizeOptimizerFailureReported;
std::atomic_flag g_clipDistanceDeclineReported;
std::atomic_flag g_clipDistanceOptimizerFailureReported;
std::atomic_flag g_clipDistanceEmulationReported;
// Varying locations the clip carriers may reach. 32 vec4s is what both backends' target
// drivers expose (128 output components); a program past it keeps the decline.
constexpr Uint32 kClipDistanceCarrierLocationBudget = 32;
} // namespace
void ProgramSpirvTask::DeferLog(String line, const Int level) {
@@ -154,8 +160,10 @@ namespace MobileGL::MG_State::GLState {
m_phaseA->in.env != nullptr && m_phaseA->in.env->DemotesTessellationPointSize();
const Bool demoteGeometryPointSize =
m_phaseA->in.env != nullptr && m_phaseA->in.env->DemotesGeometryPointSize();
// Part of the frontend fingerprint (CompileEnv), so the L1 key already separates the two.
const Bool emulateClipDistance = m_phaseA->in.env != nullptr && m_phaseA->in.env->EmulatesClipDistance();
GenerateSpirv(handoff, externalIndex, deferOutputValidationForDirectVulkan, enableSpirvValidation,
nativeFloat64, demoteTessellationPointSize, demoteGeometryPointSize);
nativeFloat64, demoteTessellationPointSize, demoteGeometryPointSize, emulateClipDistance);
// GlslangToSpv was the only consumer of the parsed ASTs; everything after this point
// works on the SPIR-V and on the TProgram's own self-contained reflection pool. Drop
// them here rather than at the end of the body, which is ~87% of this node's runtime
@@ -214,7 +222,8 @@ namespace MobileGL::MG_State::GLState {
void ProgramSpirvTask::GenerateSpirv(const ProgramLinkTask::SpirvHandoff& handoff, const Uint externalIndex,
const Bool deferOutputValidationForDirectVulkan,
const Bool enableSpirvValidation, const Bool nativeFloat64,
const Bool demoteTessellationPointSize, const Bool demoteGeometryPointSize) {
const Bool demoteTessellationPointSize, const Bool demoteGeometryPointSize,
const Bool emulateClipDistance) {
/* As we passed first stage compilation/linking,
* we'll assume all the operations here should
* pass. We may be able to employ some optimizations
@@ -269,6 +278,42 @@ namespace MobileGL::MG_State::GLState {
}
artifacts.nativeFloat64 = keepFloat64;
// The clip-distance emulation, program-wide and BEFORE the sanitize chain, on glslang's
// raw output. It cannot run after it: a stage whose only default-block uniform is the
// reserved enables member (nothing in the application reads it - only this pass does)
// has its whole MGL_GLOBAL_UBO deleted by ADCE, and the producer would then fall back
// to clipping by every distance. Running first adds the read that keeps it alive. The
// point-size demotion below places its carrier past these carriers.
artifacts.clipDistanceEmulated = false;
if (emulateClipDistance) {
ShaderCompiler::ClipDistanceEmulationOutcome outcome;
if (!ShaderCompiler::EmulateClipDistanceForProgram(
artifacts.generatedSpirv, handoff.shaderTypes, handoff.captureRequestsClipDistance,
kClipDistanceCarrierLocationBudget, outcome, !deferOutputValidationForDirectVulkan,
enableSpirvValidation)) {
DeferLog(std::format("ProgramObject {}: clip-distance emulation failed in the optimizer; the "
"program keeps gl_ClipDistance, which this backend cannot host",
externalIndex),
FirstTimeWarnLevel(g_clipDistanceOptimizerFailureReported));
} else if (outcome.emulated) {
artifacts.clipDistanceEmulated = true;
// THE ARMING SIGNAL, INFO and latched: the integration lane that pins
// MOBILEGL_CLIP_DISTANCE_EMULATION=1 asserts on this line, because a healthy
// driver renders the same pixels whether the emulation ran or not.
const Bool first = !g_clipDistanceEmulationReported.test_and_set(std::memory_order_relaxed);
DeferLog(std::format("ProgramObject {}: gl_ClipDistance emulated ({} distance(s) carried to the "
"fragment stage as varyings and clipped by discard{})",
externalIndex, outcome.distanceCount,
outcome.enablesFound ? "" : "; no enables uniform, every distance clips"),
first ? MOBILEGL_LOG_LEVEL_INFO : MOBILEGL_LOG_LEVEL_DEBUG);
} else if (!outcome.declineDetail.empty()) {
DeferLog(std::format("ProgramObject {}: clip-distance emulation declined ({}); the program keeps "
"gl_ClipDistance, which this backend cannot host",
externalIndex, outcome.declineDetail),
FirstTimeWarnLevel(g_clipDistanceDeclineReported));
}
}
// Linked SPIR-V generated, sanitize and optimize it
Bool allOptimized = true;
{
@@ -348,6 +393,7 @@ namespace MobileGL::MG_State::GLState {
artifacts.uniformOffsets.clear();
artifacts.globalUboScratch.clear();
artifacts.reservedNumSamplesOffset = ProgramObject::kInvalidUniformOffset;
artifacts.reservedClipDistanceEnablesOffset = ProgramObject::kInvalidUniformOffset;
// kInvalidUniformOffset marks locations that end up without global-UBO backing
// (e.g. the optimizer eliminated every use of the uniform); the fallback pass
// below gives those locations tail storage so glUniform* always has a target.
@@ -386,6 +432,10 @@ namespace MobileGL::MG_State::GLState {
// precisely so no application can address it - so the lookup below would find
// nothing and log it as unbacked. Only the fragment stage declares it, and
// every stage's copy sits at the same offset in the one shared global UBO.
if (name == CLIP_DISTANCE_ENABLES_UNIFORM_NAME) {
artifacts.reservedClipDistanceEnablesOffset = offset;
continue;
}
if (name == NUM_SAMPLES_UNIFORM_NAME) {
artifacts.reservedNumSamplesOffset = offset;
MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - reserved gl_NumSamples stand-in '%s' "