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path: root/source/slang/slang-ir-specialize-target-switch.cpp
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#include "slang-ir-specialize-target-switch.h"
#include "slang-ir.h"
#include "slang-ir-insts.h"
#include "slang-compiler.h"
#include "slang-capability.h"
#include "slang-ir-dce.h"

namespace Slang
{
    void specializeTargetSwitch(TargetRequest* target, IRGlobalValueWithCode* code, DiagnosticSink* sink)
    {
        if (auto gen = as<IRGeneric>(code))
        {
            auto retVal = findGenericReturnVal(gen);
            if (auto innerCode = as<IRGlobalValueWithCode>(retVal))
            {
                specializeTargetSwitch(target, innerCode, sink);
                return;
            }
        }

        bool changed = false;
        for (auto block : code->getBlocks())
        {
            bool failedImplies = false;
            if (auto targetSwitch = as<IRTargetSwitch>(block->getTerminator()))
            {
                bool isEqual;
                CapabilitySet bestCapSet = CapabilitySet::makeInvalid();
                IRBlock* targetBlock = nullptr;
                CapabilitySet::ImpliesReturnFlags impliesReturnType = CapabilitySet::ImpliesReturnFlags::NotImplied;
                for (UInt i = 0; i < targetSwitch->getCaseCount(); i++)
                {
                    auto cap = (CapabilityName)getIntVal(targetSwitch->getCaseValue(i));
                    if (target->getTargetCaps().isIncompatibleWith(cap))
                        continue;
                    CapabilitySet capSet;
                    if (cap == CapabilityName::Invalid) // `default` case
                        capSet = CapabilitySet::makeEmpty();
                    else
                        capSet = CapabilitySet(cap);
                    bool isBetterForTarget = capSet.isBetterForTarget(bestCapSet, target->getTargetCaps(), isEqual);
                    if (isBetterForTarget)
                    {
                        impliesReturnType = target->getTargetCaps().atLeastOneSetImpliedInOther(capSet);
                        bool targetImpliesCapSet = ((int)impliesReturnType & (int)CapabilitySet::ImpliesReturnFlags::Implied || capSet.isEmpty());
                        if (targetImpliesCapSet)
                        {
                            // Now check if bestCapSet contains targetCaps. If it does not then this is an invalid target
                            targetBlock = targetSwitch->getCaseBlock(i);
                            bestCapSet = capSet;
                        }
                        else
                            failedImplies = true;
                    }
                }
                IRBuilder builder(targetSwitch);
                builder.setInsertBefore(targetSwitch);
                if (targetBlock)
                {
                    builder.emitBranch(targetBlock);
                }
                else
                {
                    // only error if we have the chance of setting a valid target switch, but did not due to incompatability within same `target` atom.
                    // Otherwise we will have an issue when we process a `__target_switch() { case metal: return; }` for glsl targets.
                    if(failedImplies)
                        sink->diagnose(targetSwitch->sourceLoc, Diagnostics::profileIncompatibleWithTargetSwitch, target->getTargetCaps());
                    builder.emitMissingReturn();
                }
                targetSwitch->removeAndDeallocate();
                changed = true;
            }
        }
        if (changed)
        {
            // Remove unreachable blocks after specialization.
            eliminateDeadCode(code);
        }
    }

    void specializeTargetSwitch(TargetRequest* target, IRModule* module, DiagnosticSink* sink)
    {
        for (auto globalInst : module->getGlobalInsts())
        {
            if (auto code = as<IRGlobalValueWithCode>(globalInst))
            {
                specializeTargetSwitch(target, code, sink);
            }
        }
    }

}