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#include "slang-ir-autodiff-pairs.h"
namespace Slang
{
struct DiffPairLoweringPass : InstPassBase
{
DiffPairLoweringPass(AutoDiffSharedContext* context)
: InstPassBase(context->moduleInst->getModule()), pairBuilderStorage(context)
{
pairBuilder = &pairBuilderStorage;
}
IRInst* lowerPairType(IRBuilder* builder, IRType* pairType)
{
auto loweredPairType = pairBuilder->lowerDiffPairType(builder, pairType);
return loweredPairType;
}
IRInst* lowerMakePair(IRBuilder* builder, IRInst* inst)
{
if (auto makePairInst = as<IRMakeDifferentialPairBase>(inst))
{
auto pairType = as<IRDifferentialPairTypeBase>(makePairInst->getDataType());
builder->setInsertBefore(makePairInst);
if (auto loweredPairType = (IRType*)lowerPairType(builder, pairType))
{
if (isRuntimeType(pairType->getValueType()))
{
auto result = pairBuilder->emitExistentialMakePair(
builder,
loweredPairType,
makePairInst->getPrimalValue(),
makePairInst->getDifferentialValue());
makePairInst->replaceUsesWith(result);
makePairInst->removeAndDeallocate();
return result;
}
else if (auto typePack = as<IRTypePack>(pairType->getValueType()))
{
// TODO: Do we need to flatten the packs here?
// If the type is a type pack, then the value must be in
// MakePair(MakeValuePack(p_0, p_1, ...), MakeValuePack(d_0, d_1, ...)) form
// Convert it to MakeValuePack(MakePair(p_0, d_0), MakePair(p_1, d_1), ...)
// and lower each MakePair.
//
// Primal pack
auto primalValue = as<IRMakeValuePack>(makePairInst->getPrimalValue());
SLANG_ASSERT(primalValue);
// Differential pack
auto diffValue = as<IRMakeValuePack>(makePairInst->getDifferentialValue());
SLANG_ASSERT(diffValue);
// Expect the lowered pair type to be a type pack of pair types.
SLANG_ASSERT(as<IRTypePack>(loweredPairType));
List<IRInst*> newValues;
for (UInt i = 0; i < typePack->getOperandCount(); i++)
{
auto primalElement = primalValue->getOperand(i);
auto diffElement = diffValue->getOperand(i);
auto loweredElementPairType = (IRType*)loweredPairType->getOperand(i);
IRInst* operands[] = {primalElement, diffElement};
auto loweredMakePair =
builder->emitMakeStruct((IRType*)loweredElementPairType, 2, operands);
newValues.add(loweredMakePair);
}
auto newPack = builder->emitMakeValuePack(
loweredPairType,
newValues.getCount(),
newValues.getBuffer());
makePairInst->replaceUsesWith(newPack);
makePairInst->removeAndDeallocate();
return newPack;
}
else
{
IRInst* result = nullptr;
IRInst* operands[2] = {
makePairInst->getPrimalValue(),
makePairInst->getDifferentialValue()};
result = builder->emitMakeStruct((IRType*)(loweredPairType), 2, operands);
makePairInst->replaceUsesWith(result);
makePairInst->removeAndDeallocate();
return result;
}
}
}
return nullptr;
}
IRInst* lowerPairAccess(IRBuilder* builder, IRInst* inst)
{
if (auto getDiffInst = as<IRDifferentialPairGetDifferentialBase>(inst))
{
auto pairType = getDiffInst->getBase()->getDataType();
if (auto pairPtrType = as<IRPtrTypeBase>(pairType))
{
pairType = pairPtrType->getValueType();
}
builder->setInsertBefore(getDiffInst);
if (auto loweredType = lowerPairType(builder, pairType))
{
IRInst* diffFieldExtract = nullptr;
diffFieldExtract = pairBuilder->emitDiffFieldAccess(
builder,
(IRType*)loweredType,
getDiffInst->getBase());
getDiffInst->replaceUsesWith(diffFieldExtract);
getDiffInst->removeAndDeallocate();
return diffFieldExtract;
}
}
else if (auto getPrimalInst = as<IRDifferentialPairGetPrimalBase>(inst))
{
auto pairType = getPrimalInst->getBase()->getDataType();
if (auto pairPtrType = as<IRPtrTypeBase>(pairType))
{
pairType = pairPtrType->getValueType();
}
builder->setInsertBefore(getPrimalInst);
if (auto loweredType = lowerPairType(builder, pairType))
{
IRInst* primalFieldExtract = nullptr;
primalFieldExtract = pairBuilder->emitPrimalFieldAccess(
builder,
(IRType*)loweredType,
getPrimalInst->getBase());
getPrimalInst->replaceUsesWith(primalFieldExtract);
getPrimalInst->removeAndDeallocate();
return primalFieldExtract;
}
}
return nullptr;
}
bool processInstWithChildren(IRBuilder* builder, IRInst* instWithChildren)
{
bool modified = false;
processAllInsts(
[&](IRInst* inst)
{
// Make sure the builder is at the right level.
builder->setInsertInto(instWithChildren);
switch (inst->getOp())
{
case kIROp_DifferentialPairGetDifferential:
case kIROp_DifferentialPairGetPrimal:
case kIROp_DifferentialPairGetDifferentialUserCode:
case kIROp_DifferentialPairGetPrimalUserCode:
case kIROp_DifferentialPtrPairGetDifferential:
case kIROp_DifferentialPtrPairGetPrimal:
lowerPairAccess(builder, inst);
break;
case kIROp_MakeDifferentialPairUserCode:
case kIROp_MakeDifferentialPtrPair:
lowerMakePair(builder, inst);
break;
default:
break;
}
});
OrderedDictionary<IRInst*, IRInst*> pendingReplacements;
processAllInsts(
[&](IRInst* inst)
{
if (auto pairType = as<IRDifferentialPairTypeBase>(inst))
{
if (auto loweredType = lowerPairType(builder, pairType))
{
pendingReplacements.add(pairType, loweredType);
modified = true;
}
}
});
for (auto replacement : pendingReplacements)
{
replacement.key->replaceUsesWith(replacement.value);
replacement.key->removeAndDeallocate();
}
return modified;
}
bool processModule()
{
IRBuilder builder(module);
return processInstWithChildren(&builder, module->getModuleInst());
}
private:
DifferentialPairTypeBuilder* pairBuilder;
DifferentialPairTypeBuilder pairBuilderStorage;
};
bool processPairTypes(AutoDiffSharedContext* context)
{
DiffPairLoweringPass pairLoweringPass(context);
return pairLoweringPass.processModule();
}
struct DifferentialPairUserCodeTranscribePass : public InstPassBase
{
DifferentialPairUserCodeTranscribePass(IRModule* module)
: InstPassBase(module)
{
}
IRInst* rewritePairType(IRBuilder* builder, IRType* pairType)
{
builder->setInsertBefore(pairType);
auto originalPairType = as<IRDifferentialPairType>(pairType);
return builder->getDifferentialPairUserCodeType(
originalPairType->getValueType(),
originalPairType->getWitness());
}
IRInst* rewriteMakePair(IRBuilder* builder, IRMakeDifferentialPair* inst)
{
auto pairType = as<IRDifferentialPairType>(inst->getFullType());
builder->setInsertBefore(inst);
auto newInst = builder->emitMakeDifferentialPairUserCode(
(IRType*)pairType,
inst->getPrimalValue(),
inst->getDifferentialValue());
inst->replaceUsesWith(newInst);
inst->removeAndDeallocate();
return newInst;
}
IRInst* rewritePairAccess(IRBuilder* builder, IRInst* inst)
{
if (auto getDiffInst = as<IRDifferentialPairGetDifferential>(inst))
{
builder->setInsertBefore(inst);
auto newInst = builder->emitDifferentialPairGetDifferentialUserCode(
(IRType*)inst->getFullType(),
getDiffInst->getBase());
inst->replaceUsesWith(newInst);
inst->removeAndDeallocate();
}
else if (auto getPrimalInst = as<IRDifferentialPairGetPrimal>(inst))
{
builder->setInsertBefore(inst);
auto newInst = builder->emitDifferentialPairGetPrimalUserCode(getPrimalInst->getBase());
inst->replaceUsesWith(newInst);
inst->removeAndDeallocate();
}
return inst;
}
bool processInstWithChildren(IRBuilder* builder, IRInst* instWithChildren)
{
SLANG_UNUSED(instWithChildren);
bool modified = false;
processAllInsts(
[&](IRInst* inst)
{
switch (inst->getOp())
{
case kIROp_DifferentialPairGetDifferential:
case kIROp_DifferentialPairGetPrimal:
rewritePairAccess(builder, inst);
break;
case kIROp_MakeDifferentialPair:
rewriteMakePair(builder, as<IRMakeDifferentialPair>(inst));
break;
default:
break;
}
});
OrderedDictionary<IRInst*, IRInst*> pendingReplacements;
processInstsOfType<IRDifferentialPairType>(
kIROp_DifferentialPairType,
[&](IRDifferentialPairType* inst)
{
if (auto loweredType = rewritePairType(builder, inst))
{
pendingReplacements.add(inst, loweredType);
modified = true;
}
});
for (auto replacement : pendingReplacements)
{
replacement.key->replaceUsesWith(replacement.value);
replacement.key->removeAndDeallocate();
}
return modified;
}
bool processModule()
{
IRBuilder builder(module);
return processInstWithChildren(&builder, module->getModuleInst());
}
};
void rewriteDifferentialPairToUserCode(IRModule* module)
{
DifferentialPairUserCodeTranscribePass pairRewritePass(module);
pairRewritePass.processModule();
}
} // namespace Slang
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