Files
MobileGL/MobileGL/MG_Util/ShaderTranspiler/SpvcSession.h
T

189 lines
10 KiB
C++

// MobileGL - MobileGL/MG_Util/ShaderTranspiler/SpvcSession.h
// 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
#pragma once
#include <Includes.h>
#include <spirv_reflect.h>
#include "Types.h"
#define SPVC_CHK_INIT auto __r = SPVC_SUCCESS;
#define SPVC_CHK_RESULT(res) \
__r = res; \
if (__r != SPVC_SUCCESS) { \
return __r; \
}
#define SPVC_CHK_RETURN return __r;
namespace MobileGL {
namespace MG_Util {
namespace ShaderTranspiler {
struct SpvcType {
spvc_basetype basetype = SPVC_BASETYPE_UNKNOWN;
Uint32 vectorSize = 0;
Uint32 matCol = 0;
Bool isScalar() const { return vectorSize == 1 && matCol == 1; }
Bool isVector() const { return vectorSize > 1 && matCol == 1; }
Bool isMatrix() const { return vectorSize > 1 && matCol > 1; }
static Uint32 getByteSizeOfBaseType(const spvc_basetype type) {
switch (type) {
case SPVC_BASETYPE_INT8:
case SPVC_BASETYPE_UINT8:
return 1;
case SPVC_BASETYPE_INT16:
case SPVC_BASETYPE_UINT16:
case SPVC_BASETYPE_FP16:
return 2;
case SPVC_BASETYPE_INT32:
case SPVC_BASETYPE_UINT32:
case SPVC_BASETYPE_FP32:
return 4;
case SPVC_BASETYPE_INT64:
case SPVC_BASETYPE_UINT64:
case SPVC_BASETYPE_FP64:
return 8;
default:
return 0;
}
}
};
enum class SessionUsageBit {
Reflection = 1 << 0,
Transpile = 1 << 1,
};
struct SpvcMetadata {
UnorderedMap<String, unsigned> plainUniformOffsetsInUBO;
UnorderedMap<String, SizeT> plainUniformMemberSizesInBytes;
UnorderedMap<String, SpvcType> plainUniformMemberTypes;
// Byte stride between consecutive array elements of an arrayed plain
// uniform (0 for non-arrays). Keyed like the offset map: names are the
// flattened leaf names glslang reflection uses ("s[0].b[1].b"), without
// a trailing "[0]".
UnorderedMap<String, Uint32> plainUniformArrayStridesInUBO;
SizeT globalUboSize = 0;
};
class SpvcSession {
public:
SpvcSession() = default;
explicit SpvcSession(const Vector<unsigned int>& spirv,
Flags<SessionUsageBit> usage);
SpvcSession(SpvcSession&) = delete;
SpvcSession(SpvcSession&& that);
~SpvcSession();
SpvcSession& operator=(SpvcSession& session) = delete;
SpvcSession& operator=(SpvcSession&& that);
spvc_result CreateOptions(spvc_compiler_options* options);
spvc_result SetOptions(spvc_compiler_options options);
Vector<InterfaceVariable> GetShaderInterface(spvc_resource_type resource_type) const;
spvc_result SetVertexAttribLocation(const UnorderedMap<String, Uint>& location);
// Rewrites the Binding decoration of shader storage blocks before emission, so
// the generated source carries the EFFECTIVE binding rather than the declared
// one. This exists for the ESSL backend: glShaderStorageBlockBinding is a GL 4.3
// entry point with no ES equivalent (ES fixes a storage block's binding at link
// from its layout(binding=) qualifier), so the only place a rebinding can be
// expressed there is the qualifier the transpiler prints.
//
// Keyed by the GL interface-query name of the BLOCK (the block/type name; an
// arrayed block's elements are separate GL resources spelled "B[0]", "B[1]").
// Entries with a negative value mean "never rebound" and are skipped.
spvc_result SetShaderStorageBlockBinding(const UnorderedMap<String, Int>& bindings);
// Points every synthesized atomic-counter block at a RESERVED storage-block
// binding and reports which GL atomic-counter bindings the module declares.
//
// glslang's relaxed parse rewrote each atomic_uint into a member of
// gl_AtomicCounterBlock_<N>, where N is the GL binding the application declared;
// the block itself was then auto-mapped to whatever storage-block binding was
// free, which has no relation to N and can collide with an SSBO the application
// binds itself. Slot N is taken from the TOP of the driver's range downwards
// (`topBinding - N`) so the reserved window never overlaps the low bindings
// applications use, and a block whose slot would be negative is left alone and
// NOT reported - the caller binds nothing there rather than aliasing.
//
// `outGlBindings` is appended to, so one vector can collect a whole program's
// stages; it may repeat a binding declared by several of them.
spvc_result SetAtomicCounterBlockBindings(Int topBinding, Vector<Int>& outGlBindings);
// Drops the Index decoration from every fragment output that carries the DEFAULT
// colour index 0, so the emitted ESSL does not print `index = 0`.
//
// Index 0 is what every single-source fragment output already is, in GL and in
// ESSL alike, and SPIR-V carries the decoration only because the application
// spelled the qualifier out - `layout(location = 0, index = 0) out vec4 c;` is
// legal desktop GLSL and says nothing. Printing it back into ESSL is NOT
// harmless: GLSL ES has no `index` layout qualifier in core, so the driver
// answers "index layout qualifier requires EXT_blend_func_extended" and refuses
// the stage. The program then links nothing and every draw with it renders
// NOTHING - verified on Mesa 26.1.4 llvmpipe with no MobileGL in the process,
// and it is why KHR-GL43.shader_atomic_counters.basic-program-query read back a
// black render target.
//
// A NON-zero index is left exactly as it is: that one really does select the
// second dual-source input and cannot be expressed without the extension, so it
// must keep reaching the driver (the frontend's own glBindFragDataLocationIndexed
// path already emits only non-zero indices for the same reason).
spvc_result DropDefaultFragmentOutputColorIndex();
// Drops `readonly` and `writeonly` from every shader storage block - and every
// block member - that carries BOTH of them.
//
// GL 4.6 core 4.10 lets a buffer variable be declared readonly AND writeonly at
// once: it then cannot be read or written at all, and the only thing left that
// it can be used for is `.length()`. The pair is therefore inert by
// construction - the frontend has already rejected any access to it - so
// dropping it cannot change what the shader does.
//
// Emitting it does change whether the shader EXISTS. SPIRV-Cross hoists the
// qualifiers every member shares onto the block, and Mesa's ES compiler rejects
// that spelling outright ("Interface block sets both readonly and writeonly",
// verified on Mesa 26.1.4 llvmpipe with no MobileGL in the process, against the
// exact source this transpiler emitted). The stage then never compiles, the
// program links without it, and every dispatch or draw is a silent no-op -
// which is how KHR-GL43.shader_storage_buffer_object.basic-readonly-writeonly
// read back 0 instead of the array length.
//
// A block carrying only ONE of the two is left exactly as it is: those really do
// constrain the accesses the shader makes, and the driver is entitled to know.
spvc_result RelaxReadWriteExclusiveStorageBuffers();
spvc_result Compile(const char** result);
const SpvcMetadata& GetMetadata() const;
const char* GetLastErrorString() const;
// Should be called once, and only once, for every SPIR-V binary
spvc_result ParseMetaData();
private:
Flags<SessionUsageBit> usage{};
// SPIRV-Cross state (used when Transpile flag is set)
spvc_context context = nullptr;
spvc_parsed_ir ir = nullptr;
spvc_compiler compiler = nullptr;
spvc_compiler_options compiler_options = nullptr;
spvc_resources resources = nullptr;
// SPIRV-Reflect state (used when only Reflection flag is set)
SpvReflectShaderModule reflectModule = {};
bool reflectModuleValid = false;
SpvcMetadata metadata;
};
} // namespace ShaderTranspiler
} // namespace MG_Util
} // namespace MobileGL