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MobileGL/MobileGL/MG_Util/ShaderTranspiler/CompileEnv.cpp
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// MobileGL - MobileGL/MG_Util/ShaderTranspiler/CompileEnv.cpp
// Copyright (c) 2025-2026 MobileGL-Dev
// Licensed under the GNU Lesser General Public License v3.0:
// https://www.gnu.org/licenses/gpl-3.0.txt
// https://www.gnu.org/licenses/lgpl-3.0.txt
// SPDX-License-Identifier: LGPL-3.0-only
// End of Source File Header
#include "CompileEnv.h"
#include <MG_Backend/BackendObjects.h>
#include <MG_State/GLState/Core.h>
namespace MobileGL::MG_Util::ShaderTranspiler {
namespace {
void HashBytes(Uint64& state, const void* data, const SizeT length) {
state = static_cast<Uint64>(XXH64(data, length, state));
}
template <typename T>
void HashValue(Uint64& state, const T& value) {
static_assert(std::is_trivially_copyable_v<T>);
HashBytes(state, &value, sizeof(T));
}
} // namespace
Int ResolveMaxVertexAttribs(const Bool hasBackend, const Int backendMaxVertexAttribs) {
constexpr Int capacity = static_cast<Int>(MG_State::GLState::VertexArrayObject::MAX_VERTEX_ATTRIBS);
if (!hasBackend) return capacity;
if (backendMaxVertexAttribs <= 0) return capacity;
return std::min(backendMaxVertexAttribs, capacity);
}
Uint64 ComputeCompileEnvFingerprint(const CompileEnv& env) {
Uint64 state = 0x9e3779b97f4a7c15ull;
HashValue(state, env.maxComputeWorkGroupSize[0]);
HashValue(state, env.maxComputeWorkGroupSize[1]);
HashValue(state, env.maxComputeWorkGroupSize[2]);
HashValue(state, env.maxComputeWorkGroupCount[0]);
HashValue(state, env.maxComputeWorkGroupCount[1]);
HashValue(state, env.maxComputeWorkGroupCount[2]);
HashValue(state, env.maxComputeWorkGroupInvocations);
HashValue(state, env.backend);
// DynamicBackendParameters is a plain aggregate of scalars; hashing its object
// representation is deliberate - it means a new limit cannot be added without also
// changing the fingerprint, which is exactly the memo-hazard property wanted here.
HashBytes(state, &env.params, sizeof(env.params));
if (!env.advertisedExtensions.empty()) {
HashBytes(state, env.advertisedExtensions.data(),
env.advertisedExtensions.size() * sizeof(GLExtension));
}
return state;
}
Uint64 ComputeFrontendCompileEnvFingerprint(const CompileEnv& env) {
Uint64 state = 0xff51afd7ed558ccdull;
// The DynamicBackendParameters limits BuildTBuiltInResource copies into
// TBuiltInResource. Enumerated ONE BY ONE rather than hashed as a struct,
// deliberately: hashing all of DynamicBackendParameters would drag ~50 backend-only
// limits into a key that is supposed to be backend-agnostic, and every one of them
// would be a false miss. Keep this list in step with BuildTBuiltInResource.
HashValue(state, env.params.MaxImageUnits);
HashValue(state, env.params.MaxDrawBuffers);
HashValue(state, env.params.MaxVertexImageUniforms);
HashValue(state, env.params.MaxGeometryImageUniforms);
HashValue(state, env.params.MaxFragmentImageUniforms);
HashValue(state, env.params.MaxComputeImageUniforms);
HashValue(state, env.params.MaxCombinedImageUniforms);
// Added when wave3 (cb155c5b) made this one env-derived. It expands into the
// gl_MaxComputeTextureImageUnits built-in constant, so a compute module that reads
// that constant generates DIFFERENT SPIR-V under two backends that disagree on it.
HashValue(state, env.params.MaxComputeTextureImageUnits);
// Added when wave4 (4fc3531d) made this one env-derived, and the same class again:
// glslang REJECTS gl_ClipDistance[i] for i >= maxClipDistances at parse (ParseHelper)
// and expands gl_MaxClipDistances from the same number, so it decides both whether a
// shader compiles at all and what a module that reads the constant generates.
HashValue(state, env.params.MaxClipDistances);
// The cull-distance pair, added when the GL 4.6 API-surface wave made them env-derived:
// they were bare literals (8/8) in BuildTBuiltInResource while no backend had ever been
// asked whether it can host a cull distance. Exactly the MaxClipDistances class - glslang
// bounds gl_CullDistance[i] against maxCullDistances at parse and expands
// gl_MaxCullDistances / gl_MaxCombinedClipAndCullDistances from the same numbers.
HashValue(state, env.params.MaxCullDistances);
HashValue(state, env.params.MaxCombinedClipAndCullDistances);
// The texture-image-unit family, made env-derived in the same wave. They were stock
// glslang defaults (32/32/80) that disagreed with what glGetIntegerv answered, and
// gl_MaxTextureImageUnits / gl_MaxVertexTextureImageUnits / gl_MaxCombinedTextureImageUnits
// expand from them.
HashValue(state, env.params.MaxTextureImageUnits);
HashValue(state, env.params.MaxVertexTextureImageUnits);
HashValue(state, env.params.MaxCombinedTextureImageUnits);
// gl_MaxSamples, which also sizes gl_SampleMask[] / gl_SampleMaskIn[] and bounds a
// constant index into them, so a module that touches either generates different SPIR-V
// on two backends that report different sample counts.
HashValue(state, env.params.MaxSamples);
// The compute work-group limits, likewise added by wave3 (cb155c5b). They used to be
// hardcoded maxima in BuildTBuiltInResource, and the L1 key comment said in so many
// words that the day they became backend-derived they would have to move in here -
// that day is this merge. glslang expands BOTH of them into built-in constants
// (Initialize.cpp: "const ivec3 gl_MaxComputeWorkGroupCount = ivec3(%d,%d,%d)" and the
// same for gl_MaxComputeWorkGroupSize), so this is an INDEPENDENCE break, not merely a
// reachability one: a compute shader that reads gl_MaxComputeWorkGroupSize compiles to
// materially different SPIR-V on a driver reporting z=64 than on one reporting z=1024.
for (Uint index = 0; index < 3; ++index) {
HashValue(state, env.maxComputeWorkGroupSize[index]);
HashValue(state, env.maxComputeWorkGroupCount[index]);
}
// The two inputs to GetReflectionVertexAttribLimit. Hashed as inputs rather than as
// the resolved limit so this stays in one translation unit; that is coarser (two
// envs whose MaxVertexAttribs both exceed the storage capacity resolve to the same
// limit yet hash differently) but coarser means a false MISS, never a false hit.
HashValue(state, env.params.MaxVertexAttribs);
const Uint8 hasBackend = env.HasBackend() ? 1u : 0u;
HashValue(state, hasBackend);
return state;
}
SharedPtr<const CompileEnv> CaptureCompileEnv() {
auto env = MakeShared<CompileEnv>();
const auto& activeBackend = MG_Backend::pActiveBackendObject;
if (activeBackend) {
env->backend = activeBackend->GetBackendType();
env->params = activeBackend->GetDynamicParameters();
env->advertisedExtensions = activeBackend->GetRendererInfo().RendererGLInfo.Extensions;
}
// GL_MAX_COMPUTE_WORK_GROUP_SIZE / _COUNT. These are REAL driver calls on DirectGLES; they
// must happen here, on the context thread, and exactly once per context. The frontend
// minimum is the floor, matching what GL_Getter reports - both sides now floor at the
// shared MIN_COMPUTE_WORK_GROUP_* constants rather than at their own copy of them.
for (Uint index = 0; index < 3; ++index) {
Int backendSize = 0;
Int backendCount = 0;
if (MG_Backend::gBackendFunctionsTable.GL.GetIntegeri_v) {
MG_Backend::gBackendFunctionsTable.GL.GetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_SIZE, index,
&backendSize);
MG_Backend::gBackendFunctionsTable.GL.GetIntegeri_v(GL_MAX_COMPUTE_WORK_GROUP_COUNT, index,
&backendCount);
}
env->maxComputeWorkGroupSize[index] =
std::max(static_cast<Uint>(std::max(backendSize, 0)), MIN_COMPUTE_WORK_GROUP_SIZE[index]);
env->maxComputeWorkGroupCount[index] =
std::max(static_cast<Uint>(std::max(backendCount, 0)), MIN_COMPUTE_WORK_GROUP_COUNT[index]);
}
constexpr Uint64 kFrontendMaxComputeWorkGroupInvocations = 1024;
env->maxComputeWorkGroupInvocations =
activeBackend ? std::max(static_cast<Uint64>(std::max(env->params.MaxComputeWorkGroupInvocations, 0)),
kFrontendMaxComputeWorkGroupInvocations)
: kFrontendMaxComputeWorkGroupInvocations;
env->fingerprint = ComputeCompileEnvFingerprint(*env);
env->frontendFingerprint = ComputeFrontendCompileEnvFingerprint(*env);
return env;
}
const SharedPtr<const CompileEnv>& GetDefaultCompileEnv() {
// Function-local static, not a namespace-scope one: the fingerprint has to be
// computed, and this must not run before MG_Config is loaded.
static const SharedPtr<const CompileEnv> kDefault = [] {
auto env = MakeShared<CompileEnv>();
env->fingerprint = ComputeCompileEnvFingerprint(*env);
env->frontendFingerprint = ComputeFrontendCompileEnvFingerprint(*env);
return SharedPtr<const CompileEnv>(Move(env));
}();
return kDefault;
}
const SharedPtr<const CompileEnv>& GetCurrentCompileEnv() {
if (MG_State::pGLContext) return MG_State::pGLContext->GetCompileEnv();
return GetDefaultCompileEnv();
}
} // namespace MobileGL::MG_Util::ShaderTranspiler