[llvm-commits] RFC: initial union syntax support
Nick Lewycky
nicholas at mxc.ca
Tue May 12 23:19:28 PDT 2009
Nick Lewycky wrote:
> Andrew Lenharth wrote:
>> Updated patch. Supports C, Cpp, and all (?) native codegen. BasicAA
>> updated to be conservative (but not completely enough yet).
>
> I still don't like the fact that StructType is UnionType, but that's
> more subjective than objective.
>
> I really don't like allowing a union to contain the same type twice.
> That should be illegal no matter what the object hierarchy is.
For that matter, I just realized after sending that <union {i8, i9}> and
<union {i9, i8}> must be the same type.
Nick
>
>> Making unions a type of struct makes most code just work as most code
>> uses getOffset variants since structs can already have zero width
>> elements.
>>
>> Index: include/llvm/DerivedTypes.h
>> ===================================================================
>> --- include/llvm/DerivedTypes.h (revision 71552)
>> +++ include/llvm/DerivedTypes.h (working copy)
>> @@ -218,13 +218,17 @@
>> friend class TypeMap<StructValType, StructType>;
>> StructType(const StructType &); // Do not implement
>> const StructType &operator=(const StructType &); // Do not implement
>> - StructType(const std::vector<const Type*> &Types, bool isPacked);
>> + StructType(const std::vector<const Type*> &Types,
>> + bool isPacked, bool isUnion);
>> + enum {structPlain = 0,
>> + structPacked = 1,
>> + structUnion = 2};
>> public:
>> /// StructType::get - This static method is the primary way to create a
>> /// StructType.
>> ///
>> static StructType *get(const std::vector<const Type*> &Params,
>> - bool isPacked=false);
>> + bool isPacked=false, bool isUnion=false);
>>
>> /// StructType::get - This static method is a convenience method for
>> /// creating structure types by specifying the elements as arguments.
>> @@ -262,7 +266,9 @@
>> return T->getTypeID() == StructTyID;
>> }
>>
>> - bool isPacked() const { return (0 != getSubclassData()) ? true : false; }
>> + bool isPacked() const { return structPacked == getSubclassData(); }
>> + bool isUnion() const { return structUnion == getSubclassData(); }
>> +
>> };
>>
>>
>> Index: include/llvm/Bitcode/LLVMBitCodes.h
>> ===================================================================
>> --- include/llvm/Bitcode/LLVMBitCodes.h (revision 71552)
>> +++ include/llvm/Bitcode/LLVMBitCodes.h (working copy)
>> @@ -90,7 +90,11 @@
>> // binary compatibility.
>> TYPE_CODE_X86_FP80 = 13, // X86 LONG DOUBLE
>> TYPE_CODE_FP128 = 14, // LONG DOUBLE (112 bit mantissa)
>> - TYPE_CODE_PPC_FP128= 15 // PPC LONG DOUBLE (2 doubles)
>> + TYPE_CODE_PPC_FP128= 15, // PPC LONG DOUBLE (2 doubles)
>> +
>> + //Merge UNIOIN with STRUCT in LLVM 3.0
>> + TYPE_CODE_UNION = 16 // UNIOIN: [eltty x N]
>
> UNIOIN -> UNION, twice.
>
>> +
>> // Any other type code is assumed to be an unknown type.
>> };
>>
>> Index: docs/LangRef.html
>> ===================================================================
>> --- docs/LangRef.html (revision 71552)
>> +++ docs/LangRef.html (working copy)
>> @@ -1579,8 +1579,31 @@
>> </tr>
>> </table>
>> </div>
>> -
>> <!-- _______________________________________________________________________
>> -->
>> +<div class="doc_subsubsection"> <a name="t_ustruct">Union Structure Type</a>
>> +</div>
>> +<div class="doc_text">
>> +<h5>Overview:</h5>
>> +<p>The union structure type is used to represent a collection of data members
>> +overlapping in memory. All fields start at an offset of zero. The elements of
>> +a union structure may be any type that has a size. The size of a union is the
>> +size of the largest element. The alignment is the alignment of the
>> most restricted
>> +element.</p>
>> +<p>Structures are accessed using '<tt><a href="#i_load">load</a></tt>
>> +and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a
>> +field with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>'
>> +instruction.</p>
>> +<h5>Syntax:</h5>
>> +<pre> < union { <type list> } > <br></pre>
>> +<h5>Examples:</h5>
>> +<table class="layout">
>> + <tr class="layout">
>> + <td class="left"><tt>< union { i32, i32*, i64 } ></tt></td>
>> + <td class="left">A union of three values</td>
>> + </tr><tr class="layout">
>> +</table>
>> +</div>
>> +<!-- _______________________________________________________________________
>> -->
>> <div class="doc_subsubsection"> <a name="t_pointer">Pointer Type</a> </div>
>> <div class="doc_text">
>> <h5>Overview:</h5>
>> Index: lib/Analysis/BasicAliasAnalysis.cpp
>> ===================================================================
>> --- lib/Analysis/BasicAliasAnalysis.cpp (revision 71552)
>> +++ lib/Analysis/BasicAliasAnalysis.cpp (working copy)
>> @@ -529,6 +529,12 @@
>>
>> const PointerType *GEPPointerTy = cast<PointerType>(BasePtr1Ty);
>>
>> + //Fixme: Be conservative for Unions
>> + //Fixme: This doesn't handle embedded unions
>> + if (const StructType* STy =
>> dyn_cast<StructType>(GEPPointerTy->getElementType()))
>> + if (STy->isUnion())
>> + return MayAlias;
>> +
>> // Find the (possibly empty) initial sequence of equal values...
>> which are not
>> // necessarily constants.
>> unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops;
>> @@ -570,7 +576,6 @@
>> if (AllAreZeros) return MustAlias;
>> }
>>
>> -
>> // So now we know that the indexes derived from the base pointers,
>> // which are known to alias, are different. We can still determine a
>> // no-alias result if there are differing constant pairs in the index
>> Index: lib/Target/CBackend/CBackend.cpp
>> ===================================================================
>> --- lib/Target/CBackend/CBackend.cpp (revision 71552)
>> +++ lib/Target/CBackend/CBackend.cpp (working copy)
>> @@ -2132,7 +2132,9 @@
>> // Print out forward declarations for structure types before anything else!
>> Out << "/* Structure forward decls */\n";
>> for (; I != End; ++I) {
>> - std::string Name = "struct l_" + Mang->makeNameProper(I->first);
>> + const StructType* STy = dyn_cast<StructType>(I->second);
>> + std::string Name = ((STy && STy->isUnion()) ? "union l_" : "struct l_")
>> + + Mang->makeNameProper(I->first);
>> Out << Name << ";\n";
>> TypeNames.insert(std::make_pair(I->second, Name));
>> }
>> Index: lib/Target/CppBackend/CPPBackend.cpp
>> ===================================================================
>> --- lib/Target/CppBackend/CPPBackend.cpp (revision 71552)
>> +++ lib/Target/CppBackend/CPPBackend.cpp (working copy)
>> @@ -572,7 +572,10 @@
>> }
>> Out << "StructType* " << typeName << " = StructType::get("
>> << typeName << "_fields, /*isPacked=*/"
>> - << (ST->isPacked() ? "true" : "false") << ");";
>> + << (ST->isPacked() ? "true" : "false")
>> + << ", /*isUnion=*/"
>> + << (ST->isUnion() ? "true" : "false")
>> + << ");";
>> nl(Out);
>> break;
>> }
>> Index: lib/Target/TargetData.cpp
>> ===================================================================
>> --- lib/Target/TargetData.cpp (revision 71552)
>> +++ lib/Target/TargetData.cpp (working copy)
>> @@ -57,8 +57,13 @@
>> // Keep track of maximum alignment constraint.
>> StructAlignment = std::max(TyAlign, StructAlignment);
>>
>> - MemberOffsets[i] = StructSize;
>> - StructSize += TD.getTypeAllocSize(Ty); // Consume space for this data item
>> + if (ST->isUnion()) {
>> + MemberOffsets[i] = 0;
>> + StructSize = std::max(StructSize, TD.getTypeAllocSize(Ty));
>> + } else {
>> + MemberOffsets[i] = StructSize;
>> + StructSize += TD.getTypeAllocSize(Ty); // Consume space for
>> this data item
>> + }
>> }
>>
>> // Empty structures have alignment of 1 byte.
>> @@ -84,6 +89,7 @@
>> "Upper bound didn't work!");
>>
>> // Multiple fields can have the same offset if any of them are zero sized.
>> + // This will also happen for union structures
>> // For example, in { i32, [0 x i32], i32 }, searching for offset 4 will stop
>> // at the i32 element, because it is the last element at that
>> offset. This is
>> // the right one to return, because anything after it will have a higher
>> Index: lib/VMCore/AsmWriter.cpp
>> ===================================================================
>> --- lib/VMCore/AsmWriter.cpp (revision 71552)
>> +++ lib/VMCore/AsmWriter.cpp (working copy)
>> @@ -225,6 +225,8 @@
>> const StructType *STy = cast<StructType>(Ty);
>> if (STy->isPacked())
>> OS << '<';
>> + if (STy->isUnion())
>> + OS << "union ";
>> OS << "{ ";
>> for (StructType::element_iterator I = STy->element_begin(),
>> E = STy->element_end(); I != E; ++I) {
>> Index: lib/VMCore/Type.cpp
>> ===================================================================
>> --- lib/VMCore/Type.cpp (revision 71552)
>> +++ lib/VMCore/Type.cpp (working copy)
>> @@ -338,11 +338,13 @@
>> setAbstract(isAbstract);
>> }
>>
>> -StructType::StructType(const std::vector<const Type*> &Types, bool isPacked)
>> +StructType::StructType(const std::vector<const Type*> &Types, bool isPacked,
>> + bool isUnion)
>> : CompositeType(StructTyID) {
>> ContainedTys = reinterpret_cast<PATypeHandle*>(this + 1);
>> NumContainedTys = Types.size();
>> - setSubclassData(isPacked);
>> + assert(!(isPacked && isUnion) && "Packed union not supported");
>> + setSubclassData(isPacked + (int)isUnion * 2);
>> bool isAbstract = false;
>> for (unsigned i = 0; i < Types.size(); ++i) {
>> assert(Types[i] != Type::VoidTy && "Void type for structure field!!");
>> @@ -1107,9 +1109,11 @@
>> class StructValType {
>> std::vector<const Type*> ElTypes;
>> bool packed;
>> + bool _union;
>> public:
>> - StructValType(const std::vector<const Type*> &args, bool isPacked)
>> - : ElTypes(args), packed(isPacked) {}
>> + StructValType(const std::vector<const Type*> &args,
>> + bool isPacked, bool isUnion)
>> + : ElTypes(args), packed(isPacked), _union(isUnion) {}
>>
>> static StructValType get(const StructType *ST) {
>> std::vector<const Type *> ElTypes;
>> @@ -1117,7 +1121,7 @@
>> for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i)
>> ElTypes.push_back(ST->getElementType(i));
>>
>> - return StructValType(ElTypes, ST->isPacked());
>> + return StructValType(ElTypes, ST->isPacked(), ST->isUnion());
>> }
>>
>> static unsigned hashTypeStructure(const StructType *ST) {
>> @@ -1127,7 +1131,9 @@
>> inline bool operator<(const StructValType &STV) const {
>> if (ElTypes < STV.ElTypes) return true;
>> else if (ElTypes > STV.ElTypes) return false;
>> - else return (int)packed < (int)STV.packed;
>> + else
>> + return (int)packed + 2 * (int)_union
>> + < (int)STV.packed + 2 * (int)STV._union;
>> }
>> };
>> }
>> @@ -1135,15 +1141,15 @@
>> static ManagedStatic<TypeMap<StructValType, StructType> > StructTypes;
>>
>> StructType *StructType::get(const std::vector<const Type*> &ETypes,
>> - bool isPacked) {
>> - StructValType STV(ETypes, isPacked);
>> + bool isPacked, bool isUnion) {
>> + StructValType STV(ETypes, isPacked, isUnion);
>> StructType *ST = StructTypes->get(STV);
>> if (ST) return ST;
>>
>> // Value not found. Derive a new type!
>> ST = (StructType*) operator new(sizeof(StructType) +
>> sizeof(PATypeHandle) * ETypes.size());
>> - new (ST) StructType(ETypes, isPacked);
>> + new (ST) StructType(ETypes, isPacked, isUnion);
>> StructTypes->add(STV, ST);
>>
>> #ifdef DEBUG_MERGE_TYPES
>> Index: lib/AsmParser/LLParser.cpp
>> ===================================================================
>> --- lib/AsmParser/LLParser.cpp (revision 71552)
>> +++ lib/AsmParser/LLParser.cpp (working copy)
>> @@ -964,9 +964,15 @@
>> Result = OpaqueType::get();
>> Lex.Lex();
>> break;
>> + case lltok::kw_union:
>> + // TypeRec ::= 'union' ...
>> + Lex.Lex(); //eat the kw_union
>> + if (ParseStructType(Result, false, true))
>> + return true;
>> + break;
>> case lltok::lbrace:
>> // TypeRec ::= '{' ... '}'
>> - if (ParseStructType(Result, false))
>> + if (ParseStructType(Result, false, false))
>> return true;
>> break;
>> case lltok::lsquare:
>> @@ -979,7 +985,7 @@
>> // TypeRec ::= '<' ... '>'
>> Lex.Lex();
>> if (Lex.getKind() == lltok::lbrace) {
>> - if (ParseStructType(Result, true) ||
>> + if (ParseStructType(Result, true, false) ||
>> ParseToken(lltok::greater, "expected '>' at end of packed struct"))
>> return true;
>> } else if (ParseArrayVectorType(Result, true))
>> @@ -1222,18 +1228,22 @@
>> return false;
>> }
>>
>> -/// ParseStructType: Handles packed and unpacked types. </> parsed elsewhere.
>> +/// ParseStructType: Handles packed and unpacked types. </> and union
>> +/// parsed elsewhere.
>> /// TypeRec
>> /// ::= '{' '}'
>> /// ::= '{' TypeRec (',' TypeRec)* '}'
>> /// ::= '<' '{' '}' '>'
>> /// ::= '<' '{' TypeRec (',' TypeRec)* '}' '>'
>> -bool LLParser::ParseStructType(PATypeHolder &Result, bool Packed) {
>> +/// ::= 'union' '{' '}'
>> +/// ::= 'union' '{' TypeRec (',' TypeRec)* '}'
>> +
>> +bool LLParser::ParseStructType(PATypeHolder &Result, bool Packed, bool Union) {
>> assert(Lex.getKind() == lltok::lbrace);
>> Lex.Lex(); // Consume the '{'
>>
>> if (EatIfPresent(lltok::rbrace)) {
>> - Result = StructType::get(std::vector<const Type*>(), Packed);
>> + Result = StructType::get(std::vector<const Type*>(), Packed, Union);
>> return false;
>> }
>>
>> @@ -1261,7 +1271,7 @@
>> std::vector<const Type*> ParamsListTy;
>> for (unsigned i = 0, e = ParamsList.size(); i != e; ++i)
>> ParamsListTy.push_back(ParamsList[i].get());
>> - Result = HandleUpRefs(StructType::get(ParamsListTy, Packed));
>> + Result = HandleUpRefs(StructType::get(ParamsListTy, Packed, Union));
>> return false;
>> }
>>
>> Index: lib/AsmParser/LLLexer.cpp
>> ===================================================================
>> --- lib/AsmParser/LLLexer.cpp (revision 71552)
>> +++ lib/AsmParser/LLLexer.cpp (working copy)
>> @@ -550,6 +550,7 @@
>>
>> KEYWORD(type);
>> KEYWORD(opaque);
>> + KEYWORD(union);
>>
>> KEYWORD(eq); KEYWORD(ne); KEYWORD(slt); KEYWORD(sgt); KEYWORD(sle);
>> KEYWORD(sge); KEYWORD(ult); KEYWORD(ugt); KEYWORD(ule); KEYWORD(uge);
>> Index: lib/AsmParser/LLParser.h
>> ===================================================================
>> --- lib/AsmParser/LLParser.h (revision 71552)
>> +++ lib/AsmParser/LLParser.h (working copy)
>> @@ -147,7 +147,7 @@
>> return ParseType(Result, AllowVoid);
>> }
>> bool ParseTypeRec(PATypeHolder &H);
>> - bool ParseStructType(PATypeHolder &H, bool Packed);
>> + bool ParseStructType(PATypeHolder &H, bool Packed, bool Union);
>> bool ParseArrayVectorType(PATypeHolder &H, bool isVector);
>> bool ParseFunctionType(PATypeHolder &Result);
>> PATypeHolder HandleUpRefs(const Type *Ty);
>> Index: lib/AsmParser/LLToken.h
>> ===================================================================
>> --- lib/AsmParser/LLToken.h (revision 71552)
>> +++ lib/AsmParser/LLToken.h (working copy)
>> @@ -83,6 +83,7 @@
>>
>> kw_type,
>> kw_opaque,
>> + kw_union,
>>
>> kw_eq, kw_ne, kw_slt, kw_sgt, kw_sle, kw_sge, kw_ult, kw_ugt, kw_ule,
>> kw_uge, kw_oeq, kw_one, kw_olt, kw_ogt, kw_ole, kw_oge, kw_ord, kw_uno,
>> Index: lib/Transforms/Scalar/ScalarReplAggregates.cpp
>> ===================================================================
>> --- lib/Transforms/Scalar/ScalarReplAggregates.cpp (revision 71552)
>> +++ lib/Transforms/Scalar/ScalarReplAggregates.cpp (working copy)
>> @@ -562,8 +562,11 @@
>> // into.
>> for (; I != E; ++I) {
>> // Ignore struct elements, no extra checking needed for these.
>> - if (isa<StructType>(*I))
>> - continue;
>> + if (StructType* STy = dyn_cast<StructType>(*I))
>> + if (STy->isUnion())
>> + return MarkUnsafe(Info);
>> + else
>> + continue;
>>
>> ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
>> if (!IdxVal) return MarkUnsafe(Info);
>> @@ -1090,8 +1093,10 @@
>>
>> /// HasPadding - Return true if the specified type has any structure or
>> /// alignment padding, false otherwise.
>> +/// Unions are conservatively assumed to have padding
>> static bool HasPadding(const Type *Ty, const TargetData &TD) {
>> if (const StructType *STy = dyn_cast<StructType>(Ty)) {
>> + if (STy->isUnion()) return true;
>> const StructLayout *SL = TD.getStructLayout(STy);
>> unsigned PrevFieldBitOffset = 0;
>> for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
>> Index: lib/Bitcode/Reader/BitcodeReader.cpp
>> ===================================================================
>> --- lib/Bitcode/Reader/BitcodeReader.cpp (revision 71552)
>> +++ lib/Bitcode/Reader/BitcodeReader.cpp (working copy)
>> @@ -536,6 +536,13 @@
>> ResultTy = StructType::get(EltTys, Record[0]);
>> break;
>> }
>> + case bitc::TYPE_CODE_UNION: { // UNION: [eltty x N]
>> + std::vector<const Type*> EltTys;
>> + for (unsigned i = 0, e = Record.size(); i != e; ++i)
>> + EltTys.push_back(getTypeByID(Record[i], true));
>> + ResultTy = StructType::get(EltTys, false, true);
>> + break;
>> + }
>> case bitc::TYPE_CODE_ARRAY: // ARRAY: [numelts, eltty]
>> if (Record.size() < 2)
>> return Error("Invalid ARRAY type record");
>> Index: lib/Bitcode/Writer/BitcodeWriter.cpp
>> ===================================================================
>> --- lib/Bitcode/Writer/BitcodeWriter.cpp (revision 71552)
>> +++ lib/Bitcode/Writer/BitcodeWriter.cpp (working copy)
>> @@ -176,6 +176,14 @@
>> Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
>> Log2_32_Ceil(VE.getTypes().size()+1)));
>> unsigned StructAbbrev = Stream.EmitAbbrev(Abbv);
>> +
>> + // Abbrev for TYPE_CODE_UNION.
>> + Abbv = new BitCodeAbbrev();
>> + Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_UNION));
>> + Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
>> + Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
>> + Log2_32_Ceil(VE.getTypes().size()+1)));
>> + unsigned UnionAbbrev = Stream.EmitAbbrev(Abbv);
>>
>> // Abbrev for TYPE_CODE_ARRAY.
>> Abbv = new BitCodeAbbrev();
>> @@ -235,14 +243,25 @@
>> }
>> case Type::StructTyID: {
>> const StructType *ST = cast<StructType>(T);
>> - // STRUCT: [ispacked, eltty x N]
>> - Code = bitc::TYPE_CODE_STRUCT;
>> - TypeVals.push_back(ST->isPacked());
>> - // Output all of the element types.
>> - for (StructType::element_iterator I = ST->element_begin(),
>> - E = ST->element_end(); I != E; ++I)
>> - TypeVals.push_back(VE.getTypeID(*I));
>> - AbbrevToUse = StructAbbrev;
>> + if (!ST->isUnion()) {
>> + // STRUCT: [ispacked, eltty x N]
>> + Code = bitc::TYPE_CODE_STRUCT;
>> + TypeVals.push_back(ST->isPacked());
>> + // Output all of the element types.
>> + for (StructType::element_iterator I = ST->element_begin(),
>> + E = ST->element_end(); I != E; ++I)
>> + TypeVals.push_back(VE.getTypeID(*I));
>> + AbbrevToUse = StructAbbrev;
>> + } else {
>> + //Unify with STRUCT in LLVM 3.0
>> + // UNION: [eltty x N]
>> + Code = bitc::TYPE_CODE_UNION;
>> + // Output all of the element types.
>> + for (StructType::element_iterator I = ST->element_begin(),
>> + E = ST->element_end(); I != E; ++I)
>> + TypeVals.push_back(VE.getTypeID(*I));
>> + AbbrevToUse = UnionAbbrev;
>> + }
>> break;
>> }
>> case Type::ArrayTyID: {
>> _______________________________________________
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>>
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