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IRGen: enable the dynamic cast optimization on Windows #42286

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Merged
merged 1 commit into from
Apr 11, 2022
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IRGen: enable the dynamic cast optimization on Windows #42286

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16 changes: 14 additions & 2 deletions lib/IRGen/GenCast.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@
#include "llvm/IR/Module.h"

#include "swift/AST/ExistentialLayout.h"
#include "swift/AST/IRGenOptions.h"
#include "swift/SIL/DynamicCasts.h"
#include "swift/SIL/SILInstruction.h"
#include "swift/SIL/SILModule.h"
Expand Down Expand Up @@ -1061,8 +1062,8 @@ llvm::Value *irgen::emitFastClassCastIfPossible(IRGenFunction &IGF,
llvm::Value *instance,
CanType sourceFormalType,
CanType targetFormalType) {
if (!doesCastPreserveOwnershipForTypes(IGF.IGM.getSILModule(), sourceFormalType,
targetFormalType)) {
if (!doesCastPreserveOwnershipForTypes(IGF.IGM.getSILModule(),
sourceFormalType, targetFormalType)) {
return nullptr;
}

Expand All @@ -1089,6 +1090,17 @@ llvm::Value *irgen::emitFastClassCastIfPossible(IRGenFunction &IGF,

// Get the metadata pointer of the destination class type.
llvm::Value *destMetadata = IGF.IGM.getAddrOfTypeMetadata(targetFormalType);
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It seems that we should no longer call getAddrOfTypeMetadata for lazy initialized metadata. It looks like dead code to me.

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No, it is not dead code - it is simply unnecessary work. It is the "else" case that is being hoisted and done unconditionally. I can sink it into an else clause.

if (IGF.IGM.IRGen.Opts.LazyInitializeClassMetadata) {
llvm::Function *accessor =
IGF.IGM.getAddrOfTypeMetadataAccessFunction(targetFormalType,
NotForDefinition);
auto request = DynamicMetadataRequest(MetadataState::Complete);
// We know that we are not in a gneric class context, so we can safely
// determine that the call here does not need to take that into account.
auto response =
IGF.emitGenericTypeMetadataAccessFunctionCall(accessor, {}, request);
destMetadata = response.getMetadata();
}
llvm::Value *lhs = IGF.Builder.CreateBitCast(destMetadata, IGF.IGM.Int8PtrTy);

// Load the isa pointer.
Expand Down