[clang] [llvm] [WIP] ABI Lowering Library (PR #140112)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 11 13:29:58 PDT 2025
================
@@ -0,0 +1,1458 @@
+//===- X86.cpp ------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ABI/ABIFunctionInfo.h"
+#include "llvm/ABI/ABIInfo.h"
+#include "llvm/ABI/TargetCodegenInfo.h"
+#include "llvm/ABI/Types.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Support/Alignment.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/TypeSize.h"
+#include "llvm/TargetParser/Triple.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+
+namespace llvm {
+namespace abi {
+
+static unsigned getNativeVectorSizeForAVXABI(X86AVXABILevel AVXLevel) {
+ switch (AVXLevel) {
+ case X86AVXABILevel::AVX512:
+ return 512;
+ case X86AVXABILevel::AVX:
+ return 256;
+ case X86AVXABILevel::None:
+ return 128;
+ }
+ llvm_unreachable("Unknown AVXLevel");
+}
+
+class X86_64ABIInfo : public ABIInfo {
+public:
+ enum Class {
+ Integer = 0,
+ SSE,
+ SSEUp,
+ X87,
+ X87UP,
+ Complex_X87,
+ NoClass,
+ Memory
+ };
+
+private:
+ TypeBuilder &TB;
+ X86AVXABILevel AVXLevel;
+ bool Has64BitPointers;
+ const llvm::Triple &TargetTriple;
+
+ static Class merge(Class Accum, Class Field);
+
+ void postMerge(unsigned AggregateSize, Class &Lo, Class &Hi) const;
+
+ void classify(const Type *T, uint64_t OffsetBase, Class &Lo, Class &Hi,
+ bool IsNamedArg, bool IsRegCall = false) const;
+
+ const Type *getIntegerTypeAtOffset(const Type *IRType, unsigned IROffset,
+ const Type *SourceTy,
+ unsigned SourceOffset,
+ bool InMemory = false) const;
+
+ const Type *getSSETypeAtOffset(const Type *ABIType, unsigned ABIOffset,
+ const Type *SourceTy,
+ unsigned SourceOffset) const;
+ bool isIllegalVectorType(const Type *Ty) const;
+ bool containsMatrixField(const RecordType *RT) const;
+
+ void computeInfo(ABIFunctionInfo &FI) const override;
+ ABIArgInfo getIndirectReturnResult(const Type *Ty) const;
+ const Type *getFPTypeAtOffset(const Type *Ty, unsigned Offset) const;
+
+ const Type *isSingleElementStruct(const Type *Ty) const;
+ const Type *getByteVectorType(const Type *Ty) const;
+
+ const Type *createPairType(const Type *Lo, const Type *Hi) const;
+ ABIArgInfo getIndirectResult(const Type *Ty, unsigned FreeIntRegs) const;
+
+ ABIArgInfo classifyReturnType(const Type *RetTy) const;
+ const char *getClassName(Class C) const;
+
+ ABIArgInfo classifyArgumentType(const Type *Ty, unsigned FreeIntRegs,
+ unsigned &NeededInt, unsigned &NeededSse,
+ bool IsNamedArg,
+ bool IsRegCall = false) const;
+ const Type *useFirstFieldIfTransparentUnion(const Type *Ty) const;
+
+public:
+ X86_64ABIInfo(TypeBuilder &TypeBuilder, const Triple &Triple,
+ X86AVXABILevel AVXABILevel, bool Has64BitPtrs,
+ const ABICompatInfo &Compat)
+ : ABIInfo(Compat), TB(TypeBuilder), AVXLevel(AVXABILevel),
+ Has64BitPointers(Has64BitPtrs), TargetTriple(Triple) {}
+
+ bool has64BitPointers() const { return Has64BitPointers; }
+};
+
+// Gets the "best" type to represent the union.
+static const Type *reduceUnionForX8664(const RecordType *UnionType,
+ TypeBuilder &TB) {
+ assert(UnionType->isUnion() && "Expected union type");
+
+ ArrayRef<FieldInfo> Fields = UnionType->getFields();
+ if (Fields.empty()) {
+ return nullptr;
+ }
+
+ const Type *StorageType = nullptr;
+
+ for (const auto &Field : Fields) {
+ if (Field.IsBitField && Field.IsUnnamedBitfield &&
+ Field.BitFieldWidth == 0) {
+ continue;
+ }
+
+ const Type *FieldType = Field.FieldType;
+
+ if (UnionType->isTransparentUnion() && !StorageType) {
+ StorageType = FieldType;
+ break;
+ }
+
+ if (!StorageType ||
+ FieldType->getAlignment() > StorageType->getAlignment() ||
+ (FieldType->getAlignment() == StorageType->getAlignment() &&
+ TypeSize::isKnownGT(FieldType->getSizeInBits(),
+ StorageType->getSizeInBits()))) {
+ StorageType = FieldType;
+ }
+ }
+ return StorageType;
+}
+
+void X86_64ABIInfo::postMerge(unsigned AggregateSize, Class &Lo,
+ Class &Hi) const {
+ // AMD64-ABI 3.2.3p2: Rule 5. Then a post merger cleanup is done:
+ //
+ // (a) If one of the classes is Memory, the whole argument is passed in
+ // memory.
+ //
+ // (b) If X87UP is not preceded by X87, the whole argument is passed in
+ // memory.
+ //
+ // (c) If the size of the aggregate exceeds two eightbytes and the first
+ // eightbyte isn't SSE or any other eightbyte isn't SSEUP, the whole
+ // argument is passed in memory. NOTE: This is necessary to keep the
+ // ABI working for processors that don't support the __m256 type.
+ //
+ // (d) If SSEUP is not preceded by SSE or SSEUP, it is converted to SSE.
+ //
+ // Some of these are enforced by the merging logic. Others can arise
+ // only with unions; for example:
+ // union { _Complex double; unsigned; }
+ //
+ // Note that clauses (b) and (c) were added in 0.98.
+
+ if (Hi == Memory)
+ Lo = Memory;
+ if (Hi == X87UP && Lo != X87 && getABICompatInfo().Flags.HonorsRevision98)
+ Lo = Memory;
+ if (AggregateSize > 128 && (Lo != SSE || Hi != SSEUp))
+ Lo = Memory;
+ if (Hi == SSEUp && Lo != SSE)
+ Hi = SSE;
+}
+X86_64ABIInfo::Class X86_64ABIInfo::merge(Class Accum, Class Field) {
+ // AMD64-ABI 3.2.3p2: Rule 4. Each field of an object is
+ // classified recursively so that always two fields are
+ // considered. The resulting class is calculated according to
+ // the classes of the fields in the eightbyte:
+ //
+ // (a) If both classes are equal, this is the resulting class.
+ //
+ // (b) If one of the classes is NO_CLASS, the resulting class is
+ // the other class.
+ //
+ // (c) If one of the classes is MEMORY, the result is the MEMORY
+ // class.
+ //
+ // (d) If one of the classes is INTEGER, the result is the
+ // INTEGER.
+ //
+ // (e) If one of the classes is X87, X87UP, COMPLEX_X87 class,
+ // MEMORY is used as class.
+ //
+ // (f) Otherwise class SSE is used.
+
+ // Accum should never be memory (we should have returned) or
+ // ComplexX87 (because this cannot be passed in a structure).
+ assert((Accum != Memory && Accum != Complex_X87) &&
+ "Invalid accumulated classification during merge.");
+
+ if (Accum == Field || Field == NoClass)
+ return Accum;
+ if (Accum == NoClass)
+ return Field;
+ if (Field == Memory)
+ return Memory;
+ if (Accum == Integer || Field == Integer)
+ return Integer;
+ if (Field == X87 || Field == X87UP || Field == Complex_X87 || Accum == X87 ||
+ Accum == X87UP)
+ return Memory;
+
+ return SSE;
+}
+
+bool X86_64ABIInfo::containsMatrixField(const RecordType *RT) const {
+ for (const auto &Field : RT->getFields()) {
+ const Type *FieldType = Field.FieldType;
+
+ if (const auto *AT = dyn_cast<ArrayType>(FieldType))
+ return AT->isMatrixType();
+
+ if (const auto *NestedRT = dyn_cast<RecordType>(FieldType))
+ return containsMatrixField(NestedRT);
+ }
+ return false;
+}
+
+void X86_64ABIInfo::classify(const Type *T, uint64_t OffsetBase, Class &Lo,
+ Class &Hi, bool IsNamedArg, bool IsRegCall) const {
+ Lo = Hi = NoClass;
+ Class &Current = OffsetBase < 64 ? Lo : Hi;
+ Current = Memory;
+
+ if (T->isVoid()) {
+ Current = NoClass;
+ return;
+ }
+
+ if (const auto *IT = dyn_cast<IntegerType>(T)) {
+ auto BitWidth = IT->getSizeInBits().getFixedValue();
+
+ if (BitWidth == 128 ||
+ (IT->isBitInt() && BitWidth > 64 && BitWidth <= 128)) {
+ Lo = Integer;
+ Hi = Integer;
+ } else if (BitWidth <= 64)
+ Current = Integer;
+
+ return;
+ }
+
+ if (const auto *FT = dyn_cast<FloatType>(T)) {
+ const auto *FltSem = FT->getSemantics();
+
+ if (FltSem == &llvm::APFloat::IEEEsingle() ||
+ FltSem == &llvm::APFloat::IEEEdouble() ||
+ FltSem == &llvm::APFloat::IEEEhalf() ||
+ FltSem == &llvm::APFloat::BFloat()) {
+ Current = SSE;
+ } else if (FltSem == &llvm::APFloat::IEEEquad()) {
+ Lo = SSE;
+ Hi = SSEUp;
+ } else if (FltSem == &llvm::APFloat::x87DoubleExtended()) {
+ Lo = X87;
+ Hi = X87UP;
+ } else
+ Current = SSE;
+ return;
+ }
+ if (T->isPointer()) {
+ Current = Integer;
+ return;
+ }
+
+ if (const auto *MPT = dyn_cast<MemberPointerType>(T)) {
+ if (MPT->isFunctionPointer()) {
+ if (Has64BitPointers) {
+ Lo = Hi = Integer;
+ } else {
+ uint64_t EbFuncPtr = OffsetBase / 64;
+ uint64_t EbThisAdj = (OffsetBase + 64 - 1) / 64;
+ if (EbFuncPtr != EbThisAdj) {
+ Lo = Hi = Integer;
+ } else
+ Current = Integer;
+ }
+ } else
+ Current = Integer;
+ return;
+ }
+
+ if (const auto *VT = dyn_cast<VectorType>(T)) {
+ auto Size = VT->getSizeInBits().getFixedValue();
+ const Type *ElementType = VT->getElementType();
+
+ if (Size == 1 || Size == 8 || Size == 16 || Size == 32) {
+ // gcc passes the following as integer:
+ // 4 bytes - <4 x char>, <2 x short>, <1 x int>, <1 x float>
+ // 2 bytes - <2 x char>, <1 x short>
+ // 1 byte - <1 x char>
+ Current = Integer;
+ // If this type crosses an eightbyte boundary, it should be
+ // split.
+ uint64_t EbLo = (OffsetBase) / 64;
+ uint64_t EbHi = (OffsetBase + Size - 1) / 64;
+ if (EbLo != EbHi)
+ Hi = Lo;
+ } else if (Size == 64) {
+ if (const auto *FT = dyn_cast<FloatType>(ElementType)) {
+ // gcc passes <1 x double> in memory. :(
+ if (FT->getSemantics() == &llvm::APFloat::IEEEdouble())
+ return;
+ }
+
+ // gcc passes <1 x long long> as SSE but clang used to unconditionally
+ // pass them as integer. For platforms where clang is the de facto
+ // platform compiler, we must continue to use integer.
+ if (const auto *IT = dyn_cast<IntegerType>(ElementType)) {
+ uint64_t ElemBits = IT->getSizeInBits().getFixedValue();
+ if (!getABICompatInfo().Flags.ClassifyIntegerMMXAsSSE &&
+ (ElemBits == 64 || ElemBits == 32)) {
+ Current = Integer;
+ } else
+ Current = SSE;
+ } else
+ Current = SSE;
+ // If this type crosses an eightbyte boundary, it should be
+ // split.
+ if (OffsetBase && OffsetBase != 64)
+ Hi = Lo;
+ } else if (Size == 128 ||
+ (IsNamedArg && Size <= getNativeVectorSizeForAVXABI(AVXLevel))) {
+ if (const auto *IT = dyn_cast<IntegerType>(ElementType)) {
+ uint64_t ElemBits = IT->getSizeInBits().getFixedValue();
+ // gcc passes 256 and 512 bit <X x __int128> vectors in memory. :(
+ if (getABICompatInfo().Flags.PassInt128VectorsInMem && Size != 128 &&
+ ElemBits == 128)
+ return;
+ }
+
+ // Arguments of 256-bits are split into four eightbyte chunks. The
+ // least significant one belongs to class SSE and all the others to class
+ // SSEUP. The original Lo and Hi design considers that types can't be
+ // greater than 128-bits, so a 64-bit split in Hi and Lo makes sense.
+ // This design isn't correct for 256-bits, but since there're no cases
+ // where the upper parts would need to be inspected, avoid adding
+ // complexity and just consider Hi to match the 64-256 part.
+ //
+ // Note that per 3.5.7 of AMD64-ABI, 256-bit args are only passed in
+ // registers if they are "named", i.e. not part of the "..." of a
+ // variadic function.
+ //
+ // Similarly, per 3.2.3. of the AVX512 draft, 512-bits ("named") args are
+ // split into eight eightbyte chunks, one SSE and seven SSEUP.
+ Lo = SSE;
+ Hi = SSEUp;
+ }
+ return;
+ }
+
+ if (const auto *CT = dyn_cast<ComplexType>(T)) {
+ const Type *ElementType = CT->getElementType();
+ uint64_t Size = T->getSizeInBits().getFixedValue();
+
+ if (isa<IntegerType>(ElementType)) {
+ if (Size <= 64)
+ Current = Integer;
+ else if (Size <= 128)
+ Lo = Hi = Integer;
+ } else if (const auto *EFT = dyn_cast<FloatType>(ElementType)) {
+ const auto *FltSem = EFT->getSemantics();
+ if (FltSem == &llvm::APFloat::IEEEhalf() ||
+ FltSem == &llvm::APFloat::IEEEsingle() ||
+ FltSem == &llvm::APFloat::BFloat())
+ Current = SSE;
+ else if (FltSem == &llvm::APFloat::IEEEquad())
+ Current = Memory;
+ else if (FltSem == &llvm::APFloat::x87DoubleExtended())
+ Current = Complex_X87;
+ else if (FltSem == &llvm::APFloat::IEEEdouble())
+ Lo = Hi = SSE;
+ else
+ llvm_unreachable("Unexpected long double representation!");
+ }
+
+ uint64_t ElementSize = ElementType->getSizeInBits().getFixedValue();
+ // If this complex type crosses an eightbyte boundary then it
+ // should be split.
+ uint64_t EbReal = OffsetBase / 64;
+ uint64_t EbImag = (OffsetBase + ElementSize) / 64;
+ if (Hi == NoClass && EbReal != EbImag)
+ Hi = Lo;
+
+ return;
+ }
+
+ if (const auto *AT = dyn_cast<ArrayType>(T)) {
+ uint64_t Size = AT->getSizeInBits().getFixedValue();
+
+ if (!IsRegCall && Size > 512)
+ return;
+
+ const Type *ElementType = AT->getElementType();
+ uint64_t ElemAlign = ElementType->getAlignment().value() * 8;
+ if (OffsetBase % ElemAlign)
+ return;
+
+ Current = NoClass;
+ uint64_t EltSize = ElementType->getSizeInBits().getFixedValue();
+ uint64_t ArraySize = AT->getNumElements();
+
+ if (Size > 128 &&
+ (Size != EltSize || Size > getNativeVectorSizeForAVXABI(AVXLevel)))
+ return;
+
+ for (uint64_t I = 0, Offset = OffsetBase; I < ArraySize;
+ ++I, Offset += EltSize) {
+ Class FieldLo, FieldHi;
+ classify(ElementType, Offset, FieldLo, FieldHi, IsNamedArg);
+ Lo = merge(Lo, FieldLo);
+ Hi = merge(Hi, FieldHi);
+ if (Lo == Memory || Hi == Memory)
+ break;
+ }
+ postMerge(Size, Lo, Hi);
+ assert((Hi != SSEUp || Lo == SSE) && "Invalid SSEUp array classification.");
+ return;
+ }
+ if (const auto *RT = dyn_cast<RecordType>(T)) {
+ uint64_t Size = RT->getSizeInBits().getFixedValue();
+
+ if (containsMatrixField(RT)) {
+ Lo = Memory;
+ return;
+ }
+
+ // AMD64-ABI 3.2.3p2: Rule 1. If the size of an object is larger
+ // than eight eightbytes, ..., it has class MEMORY.
+ if (Size > 512)
+ return;
+
+ // AMD64-ABI 3.2.3p2: Rule 2. If a C++ object has either a non-trivial
+ // copy constructor or a non-trivial destructor, it is passed by invisible
+ // reference.
+ if (getRecordArgABI(RT, RT->isCXXRecord()))
+ return;
+
+ // Assume variable sized types are passed in memory.
+ if (RT->hasFlexibleArrayMember())
+ return;
+
+ // Reset Lo class, this will be recomputed.
+ Current = NoClass;
+
+ // If this is a C++ record, classify the bases first.
+ if (RT->isCXXRecord()) {
+ for (const auto &Base : RT->getBaseClasses()) {
+
+ // Classify this field.
+ //
+ // AMD64-ABI 3.2.3p2: Rule 3. If the size of the aggregate exceeds a
+ // single eightbyte, each is classified separately. Each eightbyte gets
+ // initialized to class NO_CLASS.
+ Class FieldLo, FieldHi;
+ uint64_t Offset = OffsetBase + Base.OffsetInBits;
+ classify(Base.FieldType, Offset, FieldLo, FieldHi, IsNamedArg);
+ Lo = merge(Lo, FieldLo);
+ Hi = merge(Hi, FieldHi);
+
+ if (getABICompatInfo().Flags.ReturnCXXRecordGreaterThan128InMem &&
+ (Size > 128 &&
+ (Size != Base.FieldType->getSizeInBits().getFixedValue() ||
+ Size > getNativeVectorSizeForAVXABI(AVXLevel)))) {
+ Lo = Memory;
+ postMerge(Size, Lo, Hi);
+ return;
+ }
+
+ if (Lo == Memory || Hi == Memory) {
+ postMerge(Size, Lo, Hi);
+ return;
+ }
+ }
+ }
+
+ // Classify the fields one at a time, merging the results.
+
+ bool IsUnion = RT->isUnion() && !getABICompatInfo().Flags.Clang11Compat;
+ for (const auto &Field : RT->getFields()) {
+ uint64_t Offset = OffsetBase + Field.OffsetInBits;
+ bool BitField = Field.IsBitField;
+
+ if (BitField && Field.IsUnnamedBitfield)
+ continue;
+
+ if (Size > 128 &&
+ ((!IsUnion &&
+ Size != Field.FieldType->getSizeInBits().getFixedValue()) ||
+ Size > getNativeVectorSizeForAVXABI(AVXLevel))) {
+ Lo = Memory;
+ postMerge(Size, Lo, Hi);
+ return;
+ }
+
+ bool IsInMemory = Offset % (Field.FieldType->getAlignment().value() * 8);
+ if (!BitField && IsInMemory) {
+ Lo = Memory;
+ postMerge(Size, Lo, Hi);
+ return;
+ }
+
+ Class FieldLo, FieldHi;
+
+ if (BitField) {
+ uint64_t BitFieldSize = Field.BitFieldWidth;
+ uint64_t EbLo = Offset / 64;
+ uint64_t EbHi = (Offset + BitFieldSize - 1) / 64;
+
+ if (EbLo) {
+ assert(EbHi == EbLo && "Invalid classification, type > 16 bytes.");
+ FieldLo = NoClass;
+ FieldHi = Integer;
+ } else {
+ FieldLo = Integer;
+ FieldHi = EbHi ? Integer : NoClass;
+ }
+ } else
+ classify(Field.FieldType, Offset, FieldLo, FieldHi, IsNamedArg);
+
+ Lo = merge(Lo, FieldLo);
+ Hi = merge(Hi, FieldHi);
+ if (Lo == Memory || Hi == Memory)
+ break;
+ }
+ postMerge(Size, Lo, Hi);
+ return;
+ }
+
+ Lo = Memory;
+ Hi = NoClass;
+}
+
+const Type *
+X86_64ABIInfo::useFirstFieldIfTransparentUnion(const Type *Ty) const {
+ if (const auto *RT = dyn_cast<RecordType>(Ty)) {
+ if (RT->isUnion() && RT->isTransparentUnion()) {
+ auto Fields = RT->getFields();
+ assert(!Fields.empty() && "sema created an empty transparent union");
+ return Fields.front().FieldType;
+ }
+ }
+ return Ty;
+}
+
+ABIArgInfo
+X86_64ABIInfo::classifyArgumentType(const Type *Ty, unsigned FreeIntRegs,
+ unsigned &NeededInt, unsigned &NeededSSE,
+ bool IsNamedArg, bool IsRegCall) const {
+
+ Ty = useFirstFieldIfTransparentUnion(Ty);
+
+ X86_64ABIInfo::Class Lo, Hi;
+ classify(Ty, 0, Lo, Hi, IsNamedArg, IsRegCall);
+
+ // Check some invariants
+ assert((Hi != Memory || Lo == Memory) && "Invalid memory classification.");
+ assert((Hi != SSEUp || Lo == SSE) && "Invalid SSEUp classification.");
+
+ NeededInt = 0;
+ NeededSSE = 0;
+ const Type *ResType = nullptr;
+
+ switch (Lo) {
+ case NoClass:
+ if (Hi == NoClass)
+ return ABIArgInfo::getIgnore();
+ // If the low part is just padding, it takes no register, leave ResType
+ // null.
+ assert((Hi == SSE || Hi == Integer || Hi == X87UP) &&
+ "Unknown missing lo part");
+ break;
+
+ // AMD64-ABI 3.2.3p3: Rule 1. If the class is MEMORY, pass the argument
+ // on the stack.
+ case Memory:
+ // AMD64-ABI 3.2.3p3: Rule 5. If the class is X87, X87UP or
+ // COMPLEX_X87, it is passed in memory.
+ case X87:
+ case Complex_X87:
+ if (getRecordArgABI(dyn_cast<RecordType>(Ty)) == RAA_Indirect)
+ ++NeededInt;
+ return getIndirectResult(Ty, FreeIntRegs);
+
+ case SSEUp:
+ case X87UP:
+ llvm_unreachable("Invalid classification for lo word.");
+
+ // AMD64-ABI 3.2.3p3: Rule 2. If the class is INTEGER, the next
+ // available register of the sequence %rdi, %rsi, %rdx, %rcx, %r8
+ // and %r9 is used.
+ case Integer:
+ ++NeededInt;
+
+ // Pick an 8-byte type based on the preferred type.
+ ResType = getIntegerTypeAtOffset(Ty, 0, Ty, 0);
+
+ // If we have a sign or zero extended integer, make sure to return Extend
+ // so that the parameter gets the right LLVM IR attributes.
+ if (Hi == NoClass && ResType->isInteger()) {
+ if (Ty->isInteger() && isPromotableInteger(cast<IntegerType>(Ty)))
+ return ABIArgInfo::getExtend(Ty);
+ }
+
+ if (ResType->isInteger() && ResType->getSizeInBits() == 128) {
+ assert(Hi == Integer);
+ ++NeededInt;
+ return ABIArgInfo::getDirect(ResType);
+ }
+ break;
+
+ // AMD64-ABI 3.2.3p3: Rule 3. If the class is SSE, the next
+ // available SSE register is used, the registers are taken in the
+ // order from %xmm0 to %xmm7.
+ case SSE:
+ ResType = getSSETypeAtOffset(Ty, 0, Ty, 0);
+ ++NeededSSE;
+ break;
+ }
+
+ const Type *HighPart = nullptr;
+ switch (Hi) {
+ // Memory was handled previously, Complex_X87 and X87 should
+ // never occur as hi classes, and X87UP must be preceded by X87,
+ // which is passed in memory.
+ case Memory:
+ case X87:
+ case Complex_X87:
+ llvm_unreachable("Invalid classification for hi word.");
+
+ case NoClass:
+ break;
+
+ case Integer:
+ ++NeededInt;
+ // Pick an 8-byte type based on the preferred type.
+ HighPart = getIntegerTypeAtOffset(Ty, 8, Ty, 8);
+
+ if (Lo == NoClass) // Pass HighPart at offset 8 in memory.
+ return ABIArgInfo::getDirect(HighPart, 8);
+ break;
+
+ // X87UP generally doesn't occur here (long double is passed in
+ // memory), except in situations involving unions.
+ case X87UP:
+ case SSE:
+ ++NeededSSE;
+ HighPart = getSSETypeAtOffset(Ty, 8, Ty, 8);
+
+ if (Lo == NoClass) // Pass HighPart at offset 8 in memory.
+ return ABIArgInfo::getDirect(HighPart, 8);
+ break;
+
+ // AMD64-ABI 3.2.3p3: Rule 4. If the class is SSEUP, the
+ // eightbyte is passed in the upper half of the last used SSE
+ // register. This only happens when 128-bit vectors are passed.
+ case SSEUp:
+ assert(Lo == SSE && "Unexpected SSEUp classification");
+ ResType = getByteVectorType(Ty);
+ break;
+ }
+
+ // If a high part was specified, merge it together with the low part. It is
+ // known to pass in the high eightbyte of the result. We do this by forming a
+ // first class struct aggregate with the high and low part: {low, high}
+ if (HighPart)
+ ResType = createPairType(ResType, HighPart);
+
+ return ABIArgInfo::getDirect(ResType);
+}
+
+ABIArgInfo X86_64ABIInfo::classifyReturnType(const Type *RetTy) const {
+ // AMD64-ABI 3.2.3p4: Rule 1. Classify the return type with the
+ // classification algorithm.
+
+ X86_64ABIInfo::Class Lo, Hi;
+ classify(RetTy, 0, Lo, Hi, /*isNamedArg*/ true);
+
+ // Check some invariants
+ assert((Hi != Memory || Lo == Memory) && "Invalid memory classification.");
+ assert((Hi != SSEUp || Lo == SSE) && "Invalid SSEUp classification.");
+
+ const Type *ResType = nullptr;
+ switch (Lo) {
+ case NoClass:
+ if (Hi == NoClass)
+ return ABIArgInfo::getIgnore();
+ // If the low part is just padding, it takes no register, leave ResType
+ // null.
+ assert((Hi == SSE || Hi == Integer || Hi == X87UP) &&
+ "Unknown missing lo part");
+ break;
+ case SSEUp:
+ case X87UP:
+ llvm_unreachable("Invalid classification for lo word.");
+
+ // AMD64-ABI 3.2.3p4: Rule 2. Types of class memory are returned via
+ // hidden argument.
+ case Memory:
+ return getIndirectReturnResult(RetTy);
+
+ // AMD64-ABI 3.2.3p4: Rule 3. If the class is INTEGER, the next
+ // available register of the sequence %rax, %rdx is used.
+ case Integer:
+ ResType = getIntegerTypeAtOffset(RetTy, 0, RetTy, 0);
+ // If we have a sign or zero extended integer, make sure to return Extend
+ // so that the parameter gets the right LLVM IR attributes.
+ if (Hi == NoClass && ResType->isInteger()) {
+ if (const IntegerType *IntTy = dyn_cast<IntegerType>(RetTy)) {
+ if (isPromotableInteger(IntTy)) {
+ ABIArgInfo Info = ABIArgInfo::getExtend(RetTy);
+ return Info;
+ }
+ }
+ }
+ if (ResType->isInteger() && ResType->getSizeInBits() == 128) {
+ assert(Hi == Integer);
+ return ABIArgInfo::getDirect(ResType);
+ }
+ break;
+
+ // AMD64-ABI 3.2.3p4: Rule 4. If the class is SSE, the next
+ // available SSE register of the sequence %xmm0, %xmm1 is used.
+ case SSE:
+ ResType = getSSETypeAtOffset(RetTy, 0, RetTy, 0);
+ break;
+
+ // AMD64-ABI 3.2.3p4: Rule 6. If the class is X87, the value is
+ // returned on the X87 stack in %st0 as 80-bit x87 number.
+ case X87:
+ ResType = TB.getFloatType(APFloat::x87DoubleExtended(), Align(16));
+ break;
+
+ // AMD64-ABI 3.2.3p4: Rule 8. If the class is COMPLEX_X87, the real
+ // part of the value is returned in %st0 and the imaginary part in
+ // %st1.
+ case Complex_X87:
+ assert(Hi == Complex_X87 && "Unexpected ComplexX87 classification.");
+ {
+ const Type *X87Type =
+ TB.getFloatType(APFloat::x87DoubleExtended(), Align(16));
+ FieldInfo Fields[] = {FieldInfo(X87Type, 0), FieldInfo(X87Type, 128)};
+ ResType =
+ TB.getCoercedRecordType(Fields, TypeSize::getFixed(256), Align(16));
+ }
+ break;
+ }
+
+ const Type *HighPart = nullptr;
+ switch (Hi) {
+ // Memory was handled previously and X87 should
+ // never occur as a hi class.
+ case Memory:
+ case X87:
+ llvm_unreachable("Invalid classification for hi word.");
+
+ case Complex_X87:
+ case NoClass:
+ break;
+
+ case Integer:
+ HighPart = getIntegerTypeAtOffset(RetTy, 8, RetTy, 8);
+ if (Lo == NoClass)
+ return ABIArgInfo::getDirect(HighPart, 8);
+ break;
+
+ case SSE:
+ HighPart = getSSETypeAtOffset(RetTy, 8, RetTy, 8);
+ if (Lo == NoClass)
+ return ABIArgInfo::getDirect(HighPart, 8);
+ break;
+
+ // AMD64-ABI 3.2.3p4: Rule 5. If the class is SSEUP, the eightbyte
+ // is passed in the next available eightbyte chunk if the last used
+ // vector register.
+ //
+ // SSEUP should always be preceded by SSE, just widen.
+ case SSEUp:
+ assert(Lo == SSE && "Unexpected SSEUp classification.");
+ ResType = getByteVectorType(RetTy);
+ break;
+
+ // AMD64-ABI 3.2.3p4: Rule 7. If the class is X87UP, the value is
+ // returned together with the previous X87 value in %st0.
+ case X87UP:
+ // If X87Up is preceded by X87, we don't need to do
+ // anything. However, in some cases with unions it may not be
+ // preceded by X87. In such situations we follow gcc and pass the
+ // extra bits in an SSE reg.
+ if (Lo != X87) {
+ HighPart = getSSETypeAtOffset(RetTy, 8, RetTy, 8);
+ if (Lo == NoClass) // Return HighPart at offset 8 in memory.
+ return ABIArgInfo::getDirect(HighPart, 8);
+ }
+ break;
+ }
+
+ // If a high part was specified, merge it together with the low part. It is
+ // known to pass in the high eightbyte of the result. We do this by forming a
+ // first class struct aggregate with the high and low part: {low, high}
+ if (HighPart)
+ ResType = createPairType(ResType, HighPart);
+
+ return ABIArgInfo::getDirect(ResType);
+}
+
+/// Given a high and low type that can ideally
+/// be used as elements of a two register pair to pass or return, return a
+/// first class aggregate to represent them. For example, if the low part of
+/// a by-value argument should be passed as i32* and the high part as float,
+/// return {i32*, float}.
+const Type *X86_64ABIInfo::createPairType(const Type *Lo,
+ const Type *Hi) const {
+ // In order to correctly satisfy the ABI, we need to the high part to start
+ // at offset 8. If the high and low parts we inferred are both 4-byte types
+ // (e.g. i32 and i32) then the resultant struct type ({i32,i32}) won't have
+ // the second element at offset 8. Check for this:
+ unsigned LoSize = (unsigned)Lo->getTypeAllocSize();
+ Align HiAlign = Hi->getAlignment();
+ unsigned HiStart = alignTo(LoSize, HiAlign);
+
+ assert(HiStart != 0 && HiStart <= 8 && "Invalid x86-64 argument pair!");
+
+ // To handle this, we have to increase the size of the low part so that the
+ // second element will start at an 8 byte offset. We can't increase the size
+ // of the second element because it might make us access off the end of the
+ // struct.
+ const Type *AdjustedLo = Lo;
+ if (HiStart != 8) {
+ // There are usually two sorts of types the ABI generation code can produce
+ // for the low part of a pair that aren't 8 bytes in size: half, float or
+ // i8/i16/i32. This can also include pointers when they are 32-bit (X32 and
+ // NaCl).
+ // Promote these to a larger type.
+ if (Lo->isFloat()) {
+ const FloatType *FT = cast<FloatType>(Lo);
+ if (FT->getSemantics() == &APFloat::IEEEhalf() ||
+ FT->getSemantics() == &APFloat::IEEEsingle() ||
+ FT->getSemantics() == &APFloat::BFloat())
+ AdjustedLo = TB.getFloatType(APFloat::IEEEdouble(), Align(8));
+ }
+ // Promote integers and pointers to i64
+ else if (Lo->isInteger() || Lo->isPointer())
+ AdjustedLo = TB.getIntegerType(64, Align(8), /*Signed=*/false);
+ else
+ assert((Lo->isInteger() || Lo->isPointer()) &&
+ "Invalid/unknown low type in pair");
+ unsigned AdjustedLoSize = AdjustedLo->getSizeInBits().getFixedValue() / 8;
+ HiStart = alignTo(AdjustedLoSize, HiAlign);
+ }
+
+ // Create the pair struct
+ FieldInfo Fields[] = {FieldInfo(AdjustedLo, 0), FieldInfo(Hi, HiStart * 8)};
+
+ // Verify the high part is at offset 8
+ assert((8 * 8) == Fields[1].OffsetInBits &&
+ "High part must be at offset 8 bytes");
+
+ return TB.getCoercedRecordType(Fields, TypeSize::getFixed(128), Align(8),
+ StructPacking::Default);
+}
+
+static bool bitsContainNoUserData(const Type *Ty, unsigned StartBit,
+ unsigned EndBit) {
+ // If range is completely beyond type size, it's definitely padding
+ unsigned TySize = Ty->getSizeInBits().getFixedValue();
+ if (TySize <= StartBit)
+ return true;
+
+ // Handle arrays - check each element
+ if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
+ const Type *EltTy = AT->getElementType();
+ unsigned EltSize = EltTy->getSizeInBits().getFixedValue();
+
+ for (unsigned I = 0; I < AT->getNumElements(); ++I) {
+ unsigned EltOffset = I * EltSize;
+ if (EltOffset >= EndBit)
+ break;
+
+ unsigned EltStart = (EltOffset < StartBit) ? StartBit - EltOffset : 0;
+ if (!bitsContainNoUserData(EltTy, EltStart, EndBit - EltOffset))
+ return false;
+ }
+ return true;
+ }
+
+ // Handle structs - check all fields and base classes
+ if (const RecordType *RT = dyn_cast<RecordType>(Ty)) {
+ if (RT->isUnion()) {
+ for (const auto &Field : RT->getFields()) {
+ if (Field.IsUnnamedBitfield)
+ continue;
+
+ unsigned FieldStart =
+ (Field.OffsetInBits < StartBit) ? StartBit - Field.OffsetInBits : 0;
+ unsigned FieldEnd =
+ FieldStart + Field.FieldType->getSizeInBits().getFixedValue();
+
+ // Check if field overlaps with the queried range
+ if (FieldStart < EndBit && FieldEnd > StartBit) {
+ // There's an overlap, so there is user data
+ unsigned RelativeStart =
+ (StartBit > FieldStart) ? StartBit - FieldStart : 0;
+ unsigned RelativeEnd =
+ (EndBit < FieldEnd)
+ ? EndBit - FieldStart
+ : Field.FieldType->getSizeInBits().getFixedValue();
+
+ if (!bitsContainNoUserData(Field.FieldType, RelativeStart,
+ RelativeEnd)) {
+ return false;
+ }
+ }
+ }
+ return true;
+ }
+ // Check base classes first (for C++ records)
+ if (RT->isCXXRecord()) {
+ for (unsigned I = 0; I < RT->getNumBaseClasses(); ++I) {
+ const FieldInfo &Base = RT->getBaseClasses()[I];
+ if (Base.OffsetInBits >= EndBit)
+ continue;
+
+ unsigned BaseStart =
+ (Base.OffsetInBits < StartBit) ? StartBit - Base.OffsetInBits : 0;
+ if (!bitsContainNoUserData(Base.FieldType, BaseStart,
+ EndBit - Base.OffsetInBits))
+ return false;
+ }
+ }
+
+ for (unsigned I = 0; I < RT->getNumFields(); ++I) {
+ const FieldInfo &Field = RT->getFields()[I];
+ if (Field.OffsetInBits >= EndBit)
+ break;
+
+ unsigned FieldStart =
+ (Field.OffsetInBits < StartBit) ? StartBit - Field.OffsetInBits : 0;
+ if (!bitsContainNoUserData(Field.FieldType, FieldStart,
+ EndBit - Field.OffsetInBits))
+ return false;
+ }
+ return true;
+ }
+
+ // For unions, vectors, and primitives - assume all bits are user data
+ return false;
+}
+
+const Type *X86_64ABIInfo::getIntegerTypeAtOffset(const Type *ABIType,
+ unsigned ABIOffset,
+ const Type *SourceTy,
+ unsigned SourceOffset,
+ bool InMemory) const {
+
+ const Type *WorkingType = ABIType;
+ if (InMemory && ABIType->isInteger()) {
+ const auto *IT = cast<IntegerType>(ABIType);
+ unsigned OriginalBitWidth = IT->getSizeInBits().getFixedValue();
+
+ unsigned WidenedBitWidth = OriginalBitWidth;
+ if (OriginalBitWidth <= 8) {
+ WidenedBitWidth = 8;
+ } else {
+ WidenedBitWidth = llvm::bit_ceil(OriginalBitWidth);
+ }
+
+ if (WidenedBitWidth != OriginalBitWidth) {
+ WorkingType = TB.getIntegerType(WidenedBitWidth, ABIType->getAlignment(),
+ IT->isSigned());
+ }
+ }
+ // If we're dealing with an un-offset ABI type, then it means that we're
+ // returning an 8-byte unit starting with it. See if we can safely use it.
+ if (ABIOffset == 0) {
+ // Pointers and int64's always fill the 8-byte unit.
+ if ((WorkingType->isPointer() && Has64BitPointers) ||
+ (WorkingType->isInteger() &&
+ cast<IntegerType>(WorkingType)->getSizeInBits() == 64))
+ return ABIType;
+
+ // If we have a 1/2/4-byte integer, we can use it only if the rest of the
+ // goodness in the source type is just tail padding. This is allowed to
+ // kick in for struct {double,int} on the int, but not on
+ // struct{double,int,int} because we wouldn't return the second int. We
+ // have to do this analysis on the source type because we can't depend on
+ // unions being lowered a specific way etc.
+ if ((WorkingType->isInteger() &&
+ (cast<IntegerType>(WorkingType)->getSizeInBits() == 1 ||
+ cast<IntegerType>(WorkingType)->getSizeInBits() == 8 ||
+ cast<IntegerType>(WorkingType)->getSizeInBits() == 16 ||
+ cast<IntegerType>(WorkingType)->getSizeInBits() == 32)) ||
+ (WorkingType->isPointer() && !Has64BitPointers)) {
+
+ unsigned BitWidth = WorkingType->isPointer()
+ ? 32
+ : cast<IntegerType>(WorkingType)->getSizeInBits();
+
+ if (bitsContainNoUserData(SourceTy, SourceOffset * 8 + BitWidth,
+ SourceOffset * 8 + 64))
+ return WorkingType;
+ }
+ }
+
+ if (const auto *RTy = dyn_cast<RecordType>(ABIType)) {
+ if (RTy->isUnion()) {
+ const Type *ReducedType = reduceUnionForX8664(RTy, TB);
+ if (ReducedType)
+ return getIntegerTypeAtOffset(ReducedType, ABIOffset, SourceTy,
+ SourceOffset, true);
+ }
+ if (const FieldInfo *Element =
+ RTy->getElementContainingOffset(ABIOffset * 8)) {
+
+ unsigned ElementOffsetBytes = Element->OffsetInBits / 8;
+ return getIntegerTypeAtOffset(Element->FieldType,
+ ABIOffset - ElementOffsetBytes, SourceTy,
+ SourceOffset, true);
+ }
+ }
+
+ if (const auto *ATy = dyn_cast<ArrayType>(ABIType)) {
+ const Type *EltTy = ATy->getElementType();
+ unsigned EltSize = EltTy->getSizeInBits() / 8;
+ if (EltSize > 0) {
+ unsigned EltOffset = (ABIOffset / EltSize) * EltSize;
+ return getIntegerTypeAtOffset(EltTy, ABIOffset - EltOffset, SourceTy,
+ SourceOffset, true);
+ }
+ }
+
+ // If we have a 128-bit integer, we can pass it safely using an i128
+ // so we return that
+ if (ABIType->isInteger() && ABIType->getSizeInBits() == 128) {
+ assert(ABIOffset == 0);
+ return ABIType;
+ }
+
+ unsigned TySizeInBytes =
+ llvm::divideCeil(SourceTy->getSizeInBits().getFixedValue(), 8);
+ if (auto *IT = dyn_cast<IntegerType>(SourceTy)) {
+ if (IT->isBitInt())
+ TySizeInBytes =
+ alignTo(SourceTy->getSizeInBits().getFixedValue(), 64) / 8;
+ }
+ assert(TySizeInBytes != SourceOffset && "Empty field?");
+ unsigned AvailableSize = TySizeInBytes - SourceOffset;
+ return TB.getIntegerType(std::min(AvailableSize, 8U) * 8, Align(1), false);
+}
+/// Returns the floating point type at the specified offset within a type, or
+/// nullptr if no floating point type is found at that offset.
+const Type *X86_64ABIInfo::getFPTypeAtOffset(const Type *Ty,
+ unsigned Offset) const {
+ // Check for direct match at offset 0
+ if (Offset == 0 && Ty->isFloat())
+ return Ty;
+
+ if (const ComplexType *CT = dyn_cast<ComplexType>(Ty)) {
+ const Type *ElementType = CT->getElementType();
+ unsigned ElementSize = ElementType->getSizeInBits().getFixedValue() / 8;
+
+ if (Offset == 0 || Offset == ElementSize)
+ return ElementType;
+ return nullptr;
+ }
+
+ // Handle struct types by checking each field
+ if (const RecordType *RT = dyn_cast<RecordType>(Ty)) {
+ if (const FieldInfo *Element = RT->getElementContainingOffset(Offset * 8)) {
+ unsigned ElementOffsetBytes = Element->OffsetInBits / 8;
+ return getFPTypeAtOffset(Element->FieldType, Offset - ElementOffsetBytes);
+ }
+ }
+
+ // Handle array types
+ if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
+ const Type *EltTy = AT->getElementType();
+ unsigned EltSize = EltTy->getSizeInBits() / 8;
+ unsigned EltIndex = Offset / EltSize;
+
+ return getFPTypeAtOffset(EltTy, Offset - (EltIndex * EltSize));
+ }
+
+ // No floating point type found at this offset
+ return nullptr;
+}
+
+/// Helper to check if a floating point type matches specific semantics
+static bool isFloatTypeWithSemantics(const Type *Ty,
+ const fltSemantics &Semantics) {
+ if (!Ty->isFloat())
+ return false;
+ const FloatType *FT = cast<FloatType>(Ty);
+ return FT->getSemantics() == &Semantics;
+}
+
+/// GetSSETypeAtOffset - Return a type that will be passed by the backend in the
+/// low 8 bytes of an XMM register, corresponding to the SSE class.
+const Type *X86_64ABIInfo::getSSETypeAtOffset(const Type *ABIType,
+ unsigned ABIOffset,
+ const Type *SourceTy,
+ unsigned SourceOffset) const {
+
+ if (const auto *RTy = dyn_cast<RecordType>(ABIType)) {
+ if (RTy->isUnion()) {
+ const Type *ReducedType = reduceUnionForX8664(RTy, TB);
+ if (ReducedType) {
+ return getSSETypeAtOffset(ReducedType, ABIOffset, SourceTy,
+ SourceOffset);
+ }
+ }
+ }
+
+ auto Is16bitFpTy = [](const Type *T) {
+ return isFloatTypeWithSemantics(T, APFloat::IEEEhalf()) ||
+ isFloatTypeWithSemantics(T, APFloat::BFloat());
+ };
+
+ // Get the floating point type at the requested offset
+ const Type *T0 = getFPTypeAtOffset(ABIType, ABIOffset);
+ if (!T0 || isFloatTypeWithSemantics(T0, APFloat::IEEEdouble()))
+ return TB.getFloatType(APFloat::IEEEdouble(), Align(8));
+
+ // Calculate remaining source size in bytes
+ unsigned SourceSize =
+ (SourceTy->getSizeInBits().getFixedValue() / 8) - SourceOffset;
+
+ // Try to get adjacent FP type
+ const Type *T1 = nullptr;
+ unsigned T0Size =
+ alignTo(T0->getSizeInBits().getFixedValue(), T0->getAlignment().value()) /
+ 8;
+ if (SourceSize > T0Size)
+ T1 = getFPTypeAtOffset(ABIType, ABIOffset + T0Size);
+
+ if (T1 == nullptr) {
+ if (Is16bitFpTy(T0) && SourceSize > 4)
+ T1 = getFPTypeAtOffset(ABIType, ABIOffset + 4);
+
+ if (T1 == nullptr)
+ return T0;
+ }
+ // Handle vector cases
+ if (isFloatTypeWithSemantics(T0, APFloat::IEEEsingle()) &&
+ isFloatTypeWithSemantics(T1, APFloat::IEEEsingle()))
+ return TB.getVectorType(T0, ElementCount::getFixed(2), Align(8));
+
+ if (Is16bitFpTy(T0) && Is16bitFpTy(T1)) {
+ const Type *T2 = nullptr;
+ if (SourceSize > 4)
+ T2 = getFPTypeAtOffset(ABIType, ABIOffset + 4);
+ if (!T2)
+ return TB.getVectorType(T0, ElementCount::getFixed(2), Align(8));
+ return TB.getVectorType(T0, ElementCount::getFixed(4), Align(8));
+ }
+
+ // Mixed half-float cases
+ if (Is16bitFpTy(T0) || Is16bitFpTy(T1))
+ return TB.getVectorType(TB.getFloatType(APFloat::IEEEhalf(), Align(2)),
+ ElementCount::getFixed(4), Align(8));
+
+ // Default to double
+ return TB.getFloatType(APFloat::IEEEdouble(), Align(8));
+}
+
+/// The ABI specifies that a value should be passed in a full vector XMM/YMM
+/// register. Pick an LLVM IR type that will be passed as a vector register.
+const Type *X86_64ABIInfo::getByteVectorType(const Type *Ty) const {
+ // Wrapper structs/arrays that only contain vectors are passed just like
+ // vectors; strip them off if present.
+ if (const Type *InnerTy = isSingleElementStruct(Ty))
+ Ty = InnerTy;
+
+ // Handle vector types
+ if (const VectorType *VT = dyn_cast<VectorType>(Ty)) {
+ // Don't pass vXi128 vectors in their native type, the backend can't
+ // legalize them.
+ if (getABICompatInfo().Flags.PassInt128VectorsInMem &&
+ VT->getElementType()->isInteger() &&
+ cast<IntegerType>(VT->getElementType())->getSizeInBits() == 128) {
+ unsigned Size = VT->getSizeInBits().getFixedValue();
+ return TB.getVectorType(TB.getIntegerType(64, Align(8), /*Signed=*/false),
+ ElementCount::getFixed(Size / 64),
+ Align(Size / 8));
+ }
+ return VT;
+ }
+
+ // Handle fp128
+ if (isFloatTypeWithSemantics(Ty, APFloat::IEEEquad()))
+ return Ty;
+
+ // We couldn't find the preferred IR vector type for 'Ty'.
+ unsigned Size = Ty->getSizeInBits().getFixedValue();
+ assert((Size == 128 || Size == 256 || Size == 512) && "Invalid vector size");
+
+ return TB.getVectorType(TB.getFloatType(APFloat::IEEEdouble(), Align(8)),
+ ElementCount::getFixed(Size / 64), Align(Size / 8));
+}
+
+// Returns the single element if this is a single-element struct wrapper
+const Type *X86_64ABIInfo::isSingleElementStruct(const Type *Ty) const {
+ const auto *RT = dyn_cast<RecordType>(Ty);
+ if (!RT)
+ return nullptr;
+
+ if (RT->isPolymorphic() || RT->hasNonTrivialCopyConstructor() ||
+ RT->hasNonTrivialDestructor() || RT->hasFlexibleArrayMember() ||
+ RT->getNumVirtualBaseClasses() != 0)
+ return nullptr;
----------------
nikic wrote:
That does make sense, but what I don't really get is why these things aren't checked in the existing Clang code. I think maybe the assumption is that this has already been handled previously by getRecordArgABI(), so records like that won't reach to this point? (In which case I guess the main needed property is CanPassInRegisters?)
https://github.com/llvm/llvm-project/pull/140112
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