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#include "slang-ir-lower-glsl-ssbo-types.h"
#include "slang-ir-insts.h"
#include "slang-ir.h"
namespace Slang
{
template<typename F>
static void overAllInsts(IRModule* module, F f)
{
InstWorkList workList{module};
InstHashSet workListSet{module};
workList.add(module->getModuleInst());
workListSet.add(module->getModuleInst());
while (workList.getCount())
{
const auto inst = workList.getLast();
workList.removeLast();
workListSet.remove(inst);
f(inst);
for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
{
if (workListSet.contains(child))
continue;
workList.add(child);
workListSet.add(child);
}
}
}
struct ArrayLikeSSBOInfo
{
IRType* backingStruct;
IRType* elementType;
IRStructKey* elementsKey;
};
struct StructLikeSSBOInfo
{
IRType* backingStruct;
};
struct SSBOIndexInfo
{
IRInst* ssboVar;
IRInst* index;
};
static void lowerArrayLikeSSBOs(IRModule* module)
{
// Here we will:
// - Identify SSBO types which comprise a single array field with
// element type T
// - Create a (RW)StructuredBuffer<T> type
// - Replace all uses of the SSBO with the StructuredBuffer type
Dictionary<IRGLSLShaderStorageBufferType*, ArrayLikeSSBOInfo> arrayLikeSSBOTypes;
overAllInsts(
module,
[&](IRInst* inst)
{
if (const auto ssbo = as<IRGLSLShaderStorageBufferType>(inst))
{
if (const auto backingStruct = as<IRStructType>(ssbo->getElementType()))
{
auto members = backingStruct->getFields();
if (members.getFirst() != members.getLast())
return;
const auto onlyMember = members.getFirst();
if (!onlyMember)
return;
const auto onlyArrayMember = as<IRUnsizedArrayType>(onlyMember->getFieldType());
if (!onlyArrayMember)
return;
const auto elemType = onlyArrayMember->getElementType();
arrayLikeSSBOTypes.add(ssbo, {backingStruct, elemType, onlyMember->getKey()});
}
}
});
IRBuilder builder{module};
for (const auto& [ssbo, info] : arrayLikeSSBOTypes)
{
builder.setInsertAfter(ssbo);
IRInst* operands[2] = {info.elementType, ssbo->getDataLayout()};
const auto sb = builder.getType(kIROp_HLSLRWStructuredBufferType, 2, operands);
ssbo->replaceUsesWith(sb);
ssbo->removeAndDeallocate();
Dictionary<IRInst*, SSBOIndexInfo> indexes;
traverseUses(
info.elementsKey,
[&](IRUse* use)
{
if (const auto fieldAddress = as<IRFieldAddress>(use->getUser()))
{
traverseUses(
use->user,
[&](IRUse* arrayUse)
{
if (const auto gep = as<IRGetElementPtr>(arrayUse->user))
{
SLANG_ASSERT(gep->getBase() == use->user);
indexes.add(gep, {fieldAddress->getBase(), gep->getIndex()});
}
else
{
SLANG_UNIMPLEMENTED_X("Unhandled use of array-like SSBO");
}
});
}
else if (as<IRStructField>(use->getUser()))
{
// We expect and can ignore the use when declaring a struct field
}
else
{
SLANG_UNIMPLEMENTED_X("Unhandled use of array-like SSBO");
}
});
for (const auto& [elemPtr, index] : indexes)
{
builder.setInsertBefore(elemPtr);
const auto sbp =
builder.emitRWStructuredBufferGetElementPtr(index.ssboVar, index.index);
elemPtr->replaceUsesWith(sbp);
elemPtr->removeAndDeallocate();
}
}
}
static void lowerStructLikeSSBOs(IRModule* module)
{
// Here we will:
// - Identify SSBO types without an unsized array member in the backing
// struct, T
// - Create a (RW)StructuredBuffer<T> type
// - Replace all uses of the SSBO with the StructuredBuffer type
Dictionary<IRGLSLShaderStorageBufferType*, StructLikeSSBOInfo> structLikeSSBOTypes;
overAllInsts(
module,
[&](IRInst* inst)
{
if (const auto ssbo = as<IRGLSLShaderStorageBufferType>(inst))
{
// Storage buffers are always backed by a struct
if (const auto backingStruct = as<IRStructType>(ssbo->getElementType()))
{
auto members = backingStruct->getFields();
const auto lastMember = members.getLast();
if (lastMember && as<IRUnsizedArrayType>(lastMember->getFieldType()))
return;
structLikeSSBOTypes.add(ssbo, {backingStruct});
}
}
});
// Collect the uses of these ssbos
InstHashSet ssboUses(module);
overAllInsts(
module,
[&](IRInst* inst)
{
StructLikeSSBOInfo slsi;
if (const auto ssboType = as<IRGLSLShaderStorageBufferType>(inst->getDataType()))
if (structLikeSSBOTypes.tryGetValue(ssboType, slsi))
ssboUses.add(inst);
});
IRBuilder builder{module};
for (const auto& [ssbo, info] : structLikeSSBOTypes)
{
builder.setInsertAfter(ssbo);
IRInst* operands = info.backingStruct;
const auto sb = builder.getType(kIROp_HLSLRWStructuredBufferType, 1, &operands);
ssbo->replaceUsesWith(sb);
ssbo->removeAndDeallocate();
}
for (const auto& var : *ssboUses.set)
{
traverseUses(
var,
[&](IRUse* use)
{
// We only want to insert this access into blocks, anything
// else we assume is just using the identity of the ssbo (for
// instance IRStructFieldLayoutAttr)
if (!as<IRBlock>(use->getUser()->getParent()))
return;
builder.setInsertBefore(use->getUser());
const auto sbp = builder.emitRWStructuredBufferGetElementPtr(
var,
builder.getIntValue(builder.getIntType(), 0));
use->set(sbp);
});
}
}
static void lowerSSBOsToPointers(IRModule* module)
{
IRBuilder builder{module};
overAllInsts(
module,
[&](IRInst* inst)
{
if (const auto ssbo = as<IRGLSLShaderStorageBufferType>(inst))
{
builder.setInsertAfter(ssbo);
const auto ptr = builder.getPtrType(ssbo->getElementType());
ssbo->replaceUsesWith(ptr);
ssbo->removeAndDeallocate();
}
});
}
static void diagnoseRemainingSSBOs(IRModule* module, DiagnosticSink* sink)
{
overAllInsts(
module,
[&](IRInst* inst)
{
if (const auto ssbo = as<IRGLSLShaderStorageBufferType>(inst))
{
sink->diagnose(ssbo, Diagnostics::unhandledGLSLSSBOType);
}
});
}
void lowerGLSLShaderStorageBufferObjectsToStructuredBuffers(IRModule* module, DiagnosticSink* sink)
{
lowerArrayLikeSSBOs(module);
lowerStructLikeSSBOs(module);
diagnoseRemainingSSBOs(module, sink);
}
void lowerGLSLShaderStorageBufferObjectsToPointers(IRModule* module, DiagnosticSink* sink)
{
lowerSSBOsToPointers(module);
diagnoseRemainingSSBOs(module, sink);
}
} // namespace Slang
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