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swift-mirror/lib/IRGen/GenConstant.cpp

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//===--- GenConstant.cpp - Swift IR Generation For Constants --------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file implements IR generation for constant values.
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/Constants.h"
#include "BitPatternReader.h"
#include "Explosion.h"
#include "GenConstant.h"
#include "GenEnum.h"
#include "GenIntegerLiteral.h"
#include "GenStruct.h"
#include "GenTuple.h"
#include "TypeInfo.h"
#include "StructLayout.h"
#include "Callee.h"
#include "ConstantBuilder.h"
#include "DebugTypeInfo.h"
#include "swift/IRGen/Linking.h"
#include "swift/Basic/Assertions.h"
#include "swift/Basic/Range.h"
#include "swift/SIL/SILModule.h"
#include "llvm/Support/BLAKE3.h"
using namespace swift;
using namespace irgen;
llvm::Constant *irgen::emitConstantInt(IRGenModule &IGM,
IntegerLiteralInst *ILI) {
BuiltinIntegerWidth width
= ILI->getType().castTo<AnyBuiltinIntegerType>()->getWidth();
// Handle arbitrary-precision integers.
if (width.isArbitraryWidth()) {
auto pair = emitConstantIntegerLiteral(IGM, ILI);
auto type = IGM.getIntegerLiteralTy();
return llvm::ConstantStruct::get(type, { pair.Data, pair.Flags });
}
APInt value = ILI->getValue();
// The value may need truncation if its type had an abstract size.
if (width.isPointerWidth()) {
unsigned pointerWidth = IGM.getPointerSize().getValueInBits();
assert(pointerWidth <= value.getBitWidth()
&& "lost precision at AST/SIL level?!");
if (pointerWidth < value.getBitWidth())
value = value.trunc(pointerWidth);
} else {
assert(width.isFixedWidth() && "impossible width value");
}
return llvm::ConstantInt::get(IGM.getLLVMContext(), value);
}
llvm::Constant *irgen::emitConstantZero(IRGenModule &IGM, BuiltinInst *BI) {
assert(IGM.getSILModule().getBuiltinInfo(BI->getName()).ID ==
BuiltinValueKind::ZeroInitializer);
auto helper = [&](CanType astType) -> llvm::Constant * {
if (auto type = astType->getAs<BuiltinIntegerType>()) {
APInt zero(type->getWidth().getLeastWidth(), 0);
return llvm::ConstantInt::get(IGM.getLLVMContext(), zero);
}
if (auto type = astType->getAs<BuiltinFloatType>()) {
const llvm::fltSemantics *sema = nullptr;
switch (type->getFPKind()) {
case BuiltinFloatType::IEEE16: sema = &APFloat::IEEEhalf(); break;
case BuiltinFloatType::IEEE32: sema = &APFloat::IEEEsingle(); break;
case BuiltinFloatType::IEEE64: sema = &APFloat::IEEEdouble(); break;
case BuiltinFloatType::IEEE80: sema = &APFloat::x87DoubleExtended(); break;
case BuiltinFloatType::IEEE128: sema = &APFloat::IEEEquad(); break;
case BuiltinFloatType::PPC128: sema = &APFloat::PPCDoubleDouble(); break;
}
auto zero = APFloat::getZero(*sema);
return llvm::ConstantFP::get(IGM.getLLVMContext(), zero);
}
llvm_unreachable("SIL allowed an unknown type?");
};
if (auto vector = BI->getType().getAs<BuiltinVectorType>()) {
auto zero = helper(vector.getElementType());
auto count = llvm::ElementCount::getFixed(vector->getNumElements());
return llvm::ConstantVector::getSplat(count, zero);
}
return helper(BI->getType().getASTType());
}
llvm::Constant *irgen::emitConstantFP(IRGenModule &IGM, FloatLiteralInst *FLI) {
return llvm::ConstantFP::get(IGM.getLLVMContext(), FLI->getValue());
}
llvm::Constant *irgen::emitAddrOfConstantString(IRGenModule &IGM,
StringLiteralInst *SLI) {
auto encoding = SLI->getEncoding();
bool useOSLogEncoding = encoding == StringLiteralInst::Encoding::UTF8_OSLOG;
switch (encoding) {
case StringLiteralInst::Encoding::Bytes:
case StringLiteralInst::Encoding::UTF8:
case StringLiteralInst::Encoding::UTF8_OSLOG:
return IGM.getAddrOfGlobalString(SLI->getValue(), false, useOSLogEncoding);
case StringLiteralInst::Encoding::ObjCSelector:
llvm_unreachable("cannot get the address of an Objective-C selector");
}
llvm_unreachable("bad string encoding");
}
namespace {
/// Fill in the missing values for padding.
void insertPadding(SmallVectorImpl<Explosion> &elements,
llvm::StructType *sTy) {
// fill in any gaps, which are the explicit padding that swiftc inserts.
for (unsigned i = 0, e = elements.size(); i != e; ++i) {
if (elements[i].empty()) {
auto *eltTy = sTy->getElementType(i);
assert(eltTy->isArrayTy() &&
eltTy->getArrayElementType()->isIntegerTy(8) &&
"Unexpected non-byte-array type for constant struct padding");
elements[i].add(llvm::UndefValue::get(eltTy));
}
}
}
/// Creates a struct which contains all values of `explosions`.
///
/// If all explosions have a single element and those elements match the
/// elements of `structTy`, it uses this type as result type.
/// Otherwise, it creates an anonymous struct. This can be the case for enums.
llvm::Constant *createStructFromExplosion(SmallVectorImpl<Explosion> &explosions,
llvm::StructType *structTy) {
assert(explosions.size() == structTy->getNumElements());
bool canUseStructType = true;
llvm::SmallVector<llvm::Constant *, 32> values;
unsigned idx = 0;
for (auto &elmt : explosions) {
if (elmt.size() != 1)
canUseStructType = false;
for (llvm::Value *v : elmt.claimAll()) {
if (v->getType() != structTy->getElementType(idx))
canUseStructType = false;
values.push_back(cast<llvm::Constant>(v));
}
idx++;
}
if (canUseStructType) {
return llvm::ConstantStruct::get(structTy, values);
} else {
return llvm::ConstantStruct::getAnon(values, /*Packed=*/ true);
}
}
void initWithEmptyExplosions(SmallVectorImpl<Explosion> &explosions,
unsigned count) {
for (unsigned i = 0; i < count; i++) {
explosions.push_back(Explosion());
}
}
template <typename InstTy, typename NextIndexFunc>
Explosion emitConstantStructOrTuple(IRGenModule &IGM, InstTy inst,
NextIndexFunc nextIndex, bool flatten) {
auto type = inst->getType();
auto *sTy = cast<llvm::StructType>(IGM.getTypeInfo(type).getStorageType());
SmallVector<Explosion, 32> elements;
initWithEmptyExplosions(elements, sTy->getNumElements());
for (unsigned i = 0, e = inst->getElements().size(); i != e; ++i) {
auto operand = inst->getOperand(i);
std::optional<unsigned> index = nextIndex(IGM, type, i);
if (index.has_value()) {
unsigned idx = index.value();
assert(elements[idx].empty() &&
"Unexpected constant struct field overlap");
elements[idx] = emitConstantValue(IGM, operand, flatten);
}
}
if (flatten) {
Explosion out;
for (auto &elmt : elements) {
out.add(elmt.claimAll());
}
return out;
}
insertPadding(elements, sTy);
return createStructFromExplosion(elements, sTy);
}
} // end anonymous namespace
/// Returns the usub_with_overflow builtin if \p TE extracts the result of
/// such a subtraction, which is required to have an integer_literal as right
/// operand.
static BuiltinInst *getOffsetSubtract(const TupleExtractInst *TE, SILModule &M) {
// Match the pattern:
// tuple_extract(usub_with_overflow(x, integer_literal, integer_literal 0), 0)
if (TE->getFieldIndex() != 0)
return nullptr;
auto *BI = dyn_cast<BuiltinInst>(TE->getOperand());
if (!BI)
return nullptr;
if (M.getBuiltinInfo(BI->getName()).ID != BuiltinValueKind::USubOver)
return nullptr;
if (!isa<IntegerLiteralInst>(BI->getArguments()[1]))
return nullptr;
auto *overflowFlag = dyn_cast<IntegerLiteralInst>(BI->getArguments()[2]);
if (!overflowFlag || !overflowFlag->getValue().isZero())
return nullptr;
return BI;
}
static bool isPowerOfTwo(unsigned x) {
return (x & -x) == x;
}
/// Replace i24, i40, i48 and i56 constants in `e` with the corresponding byte values.
/// Such unaligned integer constants are not correctly layed out in the data section.
static Explosion replaceUnalignedIntegerValues(IRGenModule &IGM, Explosion e) {
Explosion out;
while (!e.empty()) {
llvm::Value *v = e.claimNext();
if (auto *constInt = dyn_cast<llvm::ConstantInt>(v)) {
unsigned size = constInt->getBitWidth();
if (size % 8 == 0 && !isPowerOfTwo(size)) {
BitPatternReader reader(constInt->getValue(), IGM.Triple.isLittleEndian());
while (size > 0) {
APInt byte = reader.read(8);
out.add(llvm::ConstantInt::get(IGM.getLLVMContext(), byte));
size -= 8;
}
continue;
}
}
out.add(v);
}
return out;
}
Explosion irgen::emitConstantValue(IRGenModule &IGM, SILValue operand,
bool flatten) {
if (auto *SI = dyn_cast<StructInst>(operand)) {
// The only way to get a struct's stored properties (which we need to map to
// their physical/LLVM index) is to iterate over the properties
// progressively. Fortunately the iteration order matches the order of
// operands in a StructInst.
auto StoredProperties = SI->getStructDecl()->getStoredProperties();
auto Iter = StoredProperties.begin();
return emitConstantStructOrTuple(
IGM, SI, [&Iter](IRGenModule &IGM, SILType Type, unsigned _i) mutable {
(void)_i;
auto *FD = *Iter++;
return irgen::getPhysicalStructFieldIndex(IGM, Type, FD);
}, flatten);
} else if (auto *TI = dyn_cast<TupleInst>(operand)) {
return emitConstantStructOrTuple(IGM, TI,
irgen::getPhysicalTupleElementStructIndex,
flatten);
} else if (auto *ei = dyn_cast<EnumInst>(operand)) {
auto &strategy = getEnumImplStrategy(IGM, ei->getType());
if (strategy.emitPayloadDirectlyIntoConstant()) {
if (ei->hasOperand()) {
return emitConstantValue(IGM, ei->getOperand(), flatten);
}
return Explosion();
}
Explosion data;
if (ei->hasOperand()) {
data = emitConstantValue(IGM, ei->getOperand(), /*flatten=*/ true);
}
// Use `emitValueInjection` to create the enum constant.
// Usually this method creates code in the current function. But if all
// arguments to the enum are constant, the builder never has to emit an
// instruction. Instead it can constant fold everything and just returns
// the final constant.
IRBuilder builder(IGM.getLLVMContext(), false);
Explosion out;
strategy.emitValueInjection(IGM, builder, ei->getElement(), data, out);
return replaceUnalignedIntegerValues(IGM, std::move(out));
} else if (auto *ILI = dyn_cast<IntegerLiteralInst>(operand)) {
return emitConstantInt(IGM, ILI);
} else if (auto *FLI = dyn_cast<FloatLiteralInst>(operand)) {
return emitConstantFP(IGM, FLI);
} else if (auto *SLI = dyn_cast<StringLiteralInst>(operand)) {
return emitAddrOfConstantString(IGM, SLI);
} else if (auto *BI = dyn_cast<BuiltinInst>(operand)) {
auto args = BI->getArguments();
switch (IGM.getSILModule().getBuiltinInfo(BI->getName()).ID) {
case BuiltinValueKind::ZeroInitializer:
return emitConstantZero(IGM, BI);
case BuiltinValueKind::PtrToInt: {
auto *ptr = emitConstantValue(IGM, args[0]).claimNextConstant();
return llvm::ConstantExpr::getPtrToInt(ptr, IGM.IntPtrTy);
}
case BuiltinValueKind::IntToPtr: {
auto *num = emitConstantValue(IGM, args[0]).claimNextConstant();
return llvm::ConstantExpr::getIntToPtr(num, IGM.Int8PtrTy);
}
case BuiltinValueKind::ZExtOrBitCast: {
auto *val = emitConstantValue(IGM, args[0]).claimNextConstant();
return llvm::ConstantExpr::getZExtOrBitCast(val,
IGM.getStorageType(BI->getType()));
}
case BuiltinValueKind::StringObjectOr: {
// It is a requirement that the or'd bits in the left argument are
// initialized with 0. Therefore the or-operation is equivalent to an
// addition. We need an addition to generate a valid relocation.
auto *rhs = emitConstantValue(IGM, args[1]).claimNextConstant();
if (auto *TE = dyn_cast<TupleExtractInst>(args[0])) {
// Handle StringObjectOr(tuple_extract(usub_with_overflow(x, offset)), bits)
// This pattern appears in UTF8 String literal construction.
// Generate the equivalent: add(x, sub(bits - offset)
BuiltinInst *SubtrBI = getOffsetSubtract(TE, IGM.getSILModule());
assert(SubtrBI && "unsupported argument of StringObjectOr");
auto subArgs = SubtrBI->getArguments();
auto *ptr = emitConstantValue(IGM, subArgs[0]).claimNextConstant();
auto *offset = emitConstantValue(IGM, subArgs[1]).claimNextConstant();
auto *totalOffset = llvm::ConstantExpr::getSub(rhs, offset);
return llvm::ConstantExpr::getAdd(ptr, totalOffset);
}
auto *lhs = emitConstantValue(IGM, args[0]).claimNextConstant();
return llvm::ConstantExpr::getAdd(lhs, rhs);
}
default:
llvm_unreachable("unsupported builtin for constant expression");
}
} else if (auto *VTBI = dyn_cast<ValueToBridgeObjectInst>(operand)) {
auto *val = emitConstantValue(IGM, VTBI->getOperand()).claimNextConstant();
auto *sTy = IGM.getTypeInfo(VTBI->getType()).getStorageType();
return llvm::ConstantExpr::getIntToPtr(val, sTy);
} else if (auto *CFI = dyn_cast<ConvertFunctionInst>(operand)) {
return emitConstantValue(IGM, CFI->getOperand(), flatten);
} else if (auto *URCI = dyn_cast<UncheckedRefCastInst>(operand)) {
return emitConstantValue(IGM, URCI->getOperand(), flatten);
} else if (auto *UCI = dyn_cast<UpcastInst>(operand)) {
return emitConstantValue(IGM, UCI->getOperand(), flatten);
} else if (auto *T2TFI = dyn_cast<ThinToThickFunctionInst>(operand)) {
SILType type = operand->getType();
auto *sTy = cast<llvm::StructType>(IGM.getTypeInfo(type).getStorageType());
auto *function = llvm::ConstantExpr::getBitCast(
emitConstantValue(IGM, T2TFI->getCallee()).claimNextConstant(),
sTy->getTypeAtIndex((unsigned)0));
auto *context = llvm::ConstantExpr::getBitCast(
llvm::ConstantPointerNull::get(IGM.OpaquePtrTy),
sTy->getTypeAtIndex((unsigned)1));
if (flatten) {
Explosion out;
out.add({function, context});
return out;
}
return llvm::ConstantStruct::get(sTy, {function, context});
} else if (auto *FRI = dyn_cast<FunctionRefInst>(operand)) {
SILFunction *fn = FRI->getReferencedFunction();
llvm::Constant *fnPtr = IGM.getAddrOfSILFunction(fn, NotForDefinition);
CanSILFunctionType fnType = FRI->getType().getAs<SILFunctionType>();
if (irgen::classifyFunctionPointerKind(fn).isAsyncFunctionPointer()) {
llvm::Constant *asyncFnPtr = IGM.getAddrOfAsyncFunctionPointer(fn);
fnPtr = llvm::ConstantExpr::getBitCast(asyncFnPtr, fnPtr->getType());
}
auto authInfo = PointerAuthInfo::forFunctionPointer(IGM, fnType);
if (authInfo.isSigned()) {
auto constantDiscriminator =
cast<llvm::Constant>(authInfo.getDiscriminator());
assert(!constantDiscriminator->getType()->isPointerTy());
fnPtr = IGM.getConstantSignedPointer(fnPtr, authInfo.getKey(), nullptr,
constantDiscriminator);
}
llvm::Type *ty = IGM.getTypeInfo(FRI->getType()).getStorageType();
fnPtr = llvm::ConstantExpr::getBitCast(fnPtr, ty);
return fnPtr;
} else if (auto *gAddr = dyn_cast<GlobalAddrInst>(operand)) {
SILGlobalVariable *var = gAddr->getReferencedGlobal();
auto &ti = IGM.getTypeInfo(var->getLoweredType());
auto expansion = IGM.getResilienceExpansionForLayout(var);
assert(ti.isFixedSize(expansion));
if (ti.isKnownEmpty(expansion)) {
return llvm::ConstantPointerNull::get(IGM.OpaquePtrTy);
}
Address addr = IGM.getAddrOfSILGlobalVariable(var, ti, NotForDefinition);
return addr.getAddress();
} else if (auto *gVal = dyn_cast<GlobalValueInst>(operand)) {
assert(IGM.canMakeStaticObjectReadOnly(gVal->getType()));
SILGlobalVariable *var = gVal->getReferencedGlobal();
auto &ti = IGM.getTypeInfo(var->getLoweredType());
auto expansion = IGM.getResilienceExpansionForLayout(var);
assert(ti.isFixedSize(expansion));
Address addr = IGM.getAddrOfSILGlobalVariable(var, ti, NotForDefinition);
return addr.getAddress();
} else if (auto *atp = dyn_cast<AddressToPointerInst>(operand)) {
auto *val = emitConstantValue(IGM, atp->getOperand()).claimNextConstant();
return val;
} else {
llvm_unreachable("Unsupported SILInstruction in static initializer!");
}
}
llvm::Constant *irgen::emitConstantObject(IRGenModule &IGM, ObjectInst *OI,
StructLayout *ClassLayout) {
auto *sTy = cast<llvm::StructType>(ClassLayout->getType());
SmallVector<Explosion, 32> elements;
initWithEmptyExplosions(elements, sTy->getNumElements());
unsigned NumElems = OI->getAllElements().size();
assert(NumElems == ClassLayout->getElements().size());
// Construct the object init value including tail allocated elements.
for (unsigned i = 0; i != NumElems; ++i) {
SILValue Val = OI->getAllElements()[i];
const ElementLayout &EL = ClassLayout->getElements()[i];
if (!EL.isEmpty()) {
unsigned idx = EL.getStructIndex();
assert(idx != 0 && "the first element is the object header");
assert(elements[idx].empty() &&
"Unexpected constant struct field overlap");
elements[idx] = emitConstantValue(IGM, Val);
}
}
// Construct the object header.
llvm::StructType *ObjectHeaderTy = cast<llvm::StructType>(sTy->getElementType(0));
if (IGM.canMakeStaticObjectReadOnly(OI->getType())) {
if (!IGM.swiftImmortalRefCount) {
if (IGM.Context.LangOpts.hasFeature(Feature::Embedded)) {
// = HeapObject.immortalRefCount | HeapObject.doNotFreeBit
// 0xffff_ffff on 32-bit, 0xffff_ffff_ffff_ffff on 64-bit
IGM.swiftImmortalRefCount = llvm::ConstantInt::get(IGM.IntPtrTy, -1);
} else {
IGM.swiftImmortalRefCount = llvm::ConstantExpr::getPtrToInt(
new llvm::GlobalVariable(IGM.Module, IGM.Int8Ty,
/*constant*/ true, llvm::GlobalValue::ExternalLinkage,
/*initializer*/ nullptr, "_swiftImmortalRefCount"),
IGM.IntPtrTy);
}
}
if (!IGM.swiftStaticArrayMetadata) {
auto *classDecl = IGM.getStaticArrayStorageDecl();
assert(classDecl && "no __StaticArrayStorage in stdlib");
CanType classTy = CanType(ClassType::get(classDecl, Type(), IGM.Context));
if (IGM.Context.LangOpts.hasFeature(Feature::Embedded)) {
LinkEntity entity = LinkEntity::forTypeMetadata(classTy, TypeMetadataAddress::AddressPoint,
/*forceShared=*/ true);
// In embedded swift, the metadata for the array buffer class only needs to be very minimal:
// No vtable needed, because the object is never destructed. It only contains the null super-
// class pointer.
llvm::Constant *superClass = llvm::ConstantPointerNull::get(IGM.Int8PtrTy);
IGM.swiftStaticArrayMetadata = IGM.getAddrOfLLVMVariable(entity, superClass, DebugTypeInfo());
} else {
LinkEntity entity = LinkEntity::forTypeMetadata(classTy, TypeMetadataAddress::AddressPoint);
IGM.swiftStaticArrayMetadata = IGM.getAddrOfLLVMVariable(entity, NotForDefinition, DebugTypeInfo());
}
}
elements[0].add(llvm::ConstantStruct::get(ObjectHeaderTy, {
IGM.swiftStaticArrayMetadata,
IGM.swiftImmortalRefCount }));
} else {
elements[0].add(llvm::Constant::getNullValue(ObjectHeaderTy));
}
insertPadding(elements, sTy);
return createStructFromExplosion(elements, sTy);
}
void ConstantAggregateBuilderBase::addUniqueHash(StringRef data) {
llvm::BLAKE3 hasher;
hasher.update(data);
auto rawHash = hasher.final();
auto truncHash = llvm::ArrayRef(rawHash).slice(0, NumBytes_UniqueHash);
add(llvm::ConstantDataArray::get(IGM().getLLVMContext(), truncHash));
}