redgpu/ispc: Intel® Implicit SPMD Program Compiler

src/decl.cpp
725 строк26 KB
Dmitry Babokin
Introducing ispc namespace
27 апр 2021, 08:46
27 апр 2021, 08:46021885b
/*
  Copyright (c) 2010-2021, Intel Corporation
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

    * Neither the name of Intel Corporation nor the names of its
      contributors may be used to endorse or promote products derived from
      this software without specific prior written permission.


   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/** @file decl.cpp
    @brief Implementations of classes related to turning declarations into
           symbol names and types.
*/

#include "decl.h"
#include "expr.h"
#include "module.h"
#include "stmt.h"
#include "sym.h"
#include "type.h"
#include "util.h"

#include <set>
#include <stdio.h>
#include <string.h>

using namespace ispc;

static void lPrintTypeQualifiers(int typeQualifiers) {
    if (typeQualifiers & TYPEQUAL_INLINE)
        printf("inline ");
    if (typeQualifiers & TYPEQUAL_CONST)
        printf("const ");
    if (typeQualifiers & TYPEQUAL_UNIFORM)
        printf("uniform ");
    if (typeQualifiers & TYPEQUAL_VARYING)
        printf("varying ");
    if (typeQualifiers & TYPEQUAL_TASK)
        printf("task ");
    if (typeQualifiers & TYPEQUAL_SIGNED)
        printf("signed ");
    if (typeQualifiers & TYPEQUAL_UNSIGNED)
        printf("unsigned ");
    if (typeQualifiers & TYPEQUAL_EXPORT)
        printf("export ");
    if (typeQualifiers & TYPEQUAL_UNMASKED)
        printf("unmasked ");
}

/** Given a Type and a set of type qualifiers, apply the type qualifiers to
    the type, returning the type that is the result.
*/
static const Type *lApplyTypeQualifiers(int typeQualifiers, const Type *type, SourcePos pos) {
    if (type == NULL)
        return NULL;

    if ((typeQualifiers & TYPEQUAL_CONST) != 0) {
        type = type->GetAsConstType();
    }

    if (((typeQualifiers & TYPEQUAL_UNIFORM) != 0) && ((typeQualifiers & TYPEQUAL_VARYING) != 0)) {
        Error(pos, "Type \"%s\" cannot be qualified with both uniform and varying.", type->GetString().c_str());
    }

    if ((typeQualifiers & TYPEQUAL_UNIFORM) != 0) {
        if (type->IsVoidType())
            Error(pos, "\"uniform\" qualifier is illegal with \"void\" type.");
        else
            type = type->GetAsUniformType();
    } else if ((typeQualifiers & TYPEQUAL_VARYING) != 0) {
        if (type->IsVoidType())
            Error(pos, "\"varying\" qualifier is illegal with \"void\" type.");
        else
            type = type->GetAsVaryingType();
    } else {
        if (type->IsVoidType() == false)
            type = type->GetAsUnboundVariabilityType();
    }

    if ((typeQualifiers & TYPEQUAL_UNSIGNED) != 0) {
        if ((typeQualifiers & TYPEQUAL_SIGNED) != 0)
            Error(pos, "Illegal to apply both \"signed\" and \"unsigned\" "
                       "qualifiers.");

        const Type *unsignedType = type->GetAsUnsignedType();
        if (unsignedType != NULL)
            type = unsignedType;
        else {
            const Type *resolvedType = type->ResolveUnboundVariability(Variability::Varying);
            Error(pos, "\"unsigned\" qualifier is illegal with \"%s\" type.", resolvedType->GetString().c_str());
        }
    }

    if ((typeQualifiers & TYPEQUAL_SIGNED) != 0 && type->IsIntType() == false) {
        const Type *resolvedType = type->ResolveUnboundVariability(Variability::Varying);
        Error(pos,
              "\"signed\" qualifier is illegal with non-integer type "
              "\"%s\".",
              resolvedType->GetString().c_str());
    }

    return type;
}

///////////////////////////////////////////////////////////////////////////
// DeclSpecs

DeclSpecs::DeclSpecs(const Type *t, StorageClass sc, int tq) {
    baseType = t;
    storageClass = sc;
    typeQualifiers = tq;
    soaWidth = 0;
    vectorSize = 0;
    if (t != NULL) {
        if (m->symbolTable->ContainsType(t)) {
            // Typedefs might have uniform/varying qualifiers inside.
            if (t->IsVaryingType()) {
                typeQualifiers |= TYPEQUAL_VARYING;
            } else if (t->IsUniformType()) {
                typeQualifiers |= TYPEQUAL_UNIFORM;
            }
        }
    }
}

const Type *DeclSpecs::GetBaseType(SourcePos pos) const {
    const Type *retType = baseType;

    if (retType == NULL) {
        Warning(pos, "No type specified in declaration.  Assuming int32.");
        retType = AtomicType::UniformInt32->GetAsUnboundVariabilityType();
    }

    if (vectorSize > 0) {
        const AtomicType *atomicType = CastType<AtomicType>(retType);
        if (atomicType == NULL) {
            Error(pos, "Only atomic types (int, float, ...) are legal for vector "
                       "types.");
            return NULL;
        }
        retType = new VectorType(atomicType, vectorSize);
    }

    retType = lApplyTypeQualifiers(typeQualifiers, retType, pos);

    if (soaWidth > 0) {
        const StructType *st = CastType<StructType>(retType);

        if (st == NULL) {
            Error(pos,
                  "Illegal to provide soa<%d> qualifier with non-struct "
                  "type \"%s\".",
                  soaWidth, retType ? retType->GetString().c_str() : "NULL");
            return NULL;
        } else if (soaWidth <= 0 || (soaWidth & (soaWidth - 1)) != 0) {
            Error(pos,
                  "soa<%d> width illegal. Value must be positive power "
                  "of two.",
                  soaWidth);
            return NULL;
        }

        if (st->IsUniformType()) {
            Error(pos,
                  "\"uniform\" qualifier and \"soa<%d>\" qualifier can't "
                  "both be used in a type declaration.",
                  soaWidth);
            return NULL;
        } else if (st->IsVaryingType()) {
            Error(pos,
                  "\"varying\" qualifier and \"soa<%d>\" qualifier can't "
                  "both be used in a type declaration.",
                  soaWidth);
            return NULL;
        } else
            retType = st->GetAsSOAType(soaWidth);

        if (soaWidth < g->target->getVectorWidth())
            PerformanceWarning(pos,
                               "soa<%d> width smaller than gang size %d "
                               "currently leads to inefficient code to access "
                               "soa types.",
                               soaWidth, g->target->getVectorWidth());
    }

    return retType;
}

static const char *lGetStorageClassName(StorageClass storageClass) {
    switch (storageClass) {
    case SC_NONE:
        return "";
    case SC_EXTERN:
        return "extern";
    case SC_EXTERN_C:
        return "extern \"C\"";
    case SC_STATIC:
        return "static";
    case SC_TYPEDEF:
        return "typedef";
    default:
        FATAL("Unhandled storage class in lGetStorageClassName");
        return "";
    }
}

void DeclSpecs::Print() const {
    printf("Declspecs: [%s ", lGetStorageClassName(storageClass));

    if (soaWidth > 0)
        printf("soa<%d> ", soaWidth);
    lPrintTypeQualifiers(typeQualifiers);
    printf("base type: %s", baseType->GetString().c_str());

    if (vectorSize > 0)
        printf("<%d>", vectorSize);
    printf("]");
}

///////////////////////////////////////////////////////////////////////////
// Declarator

Declarator::Declarator(DeclaratorKind dk, SourcePos p) : pos(p), kind(dk) {
    child = NULL;
    typeQualifiers = 0;
    storageClass = SC_NONE;
    arraySize = -1;
    type = NULL;
    initExpr = NULL;
}

void Declarator::InitFromDeclSpecs(DeclSpecs *ds) {
    const Type *baseType = ds->GetBaseType(pos);

    InitFromType(baseType, ds);

    if (type == NULL) {
        AssertPos(pos, m->errorCount > 0);
        return;
    }

    storageClass = ds->storageClass;

    if (ds->declSpecList.size() > 0 && CastType<FunctionType>(type) == NULL) {
        Error(pos,
              "__declspec specifiers for non-function type \"%s\" are "
              "not used.",
              type->GetString().c_str());
    }
}

void Declarator::Print(int indent) const {
    printf("%*cdeclarator: [", indent, ' ');
    pos.Print();

    lPrintTypeQualifiers(typeQualifiers);
    printf("%s ", lGetStorageClassName(storageClass));
    if (name.size() > 0)
        printf("%s", name.c_str());
    else
        printf("(unnamed)");

    printf(", array size = %d", arraySize);

    printf(", kind = ");
    switch (kind) {
    case DK_BASE:
        printf("base");
        break;
    case DK_POINTER:
        printf("pointer");
        break;
    case DK_REFERENCE:
        printf("reference");
        break;
    case DK_ARRAY:
        printf("array");
        break;
    case DK_FUNCTION:
        printf("function");
        break;
    default:
        FATAL("Unhandled declarator kind");
    }

    if (initExpr != NULL) {
        printf(" = (");
        initExpr->Print();
        printf(")");
    }

    if (functionParams.size() > 0) {
        for (unsigned int i = 0; i < functionParams.size(); ++i) {
            printf("\n%*cfunc param %d:\n", indent, ' ', i);
            functionParams[i]->Print(indent + 4);
        }
    }

    if (child != NULL)
        child->Print(indent + 4);

    printf("]\n");
}

void Declarator::InitFromType(const Type *baseType, DeclSpecs *ds) {
    bool hasUniformQual = ((typeQualifiers & TYPEQUAL_UNIFORM) != 0);
    bool hasVaryingQual = ((typeQualifiers & TYPEQUAL_VARYING) != 0);
    bool isTask = ((typeQualifiers & TYPEQUAL_TASK) != 0);
    bool isExported = ((typeQualifiers & TYPEQUAL_EXPORT) != 0);
    bool isConst = ((typeQualifiers & TYPEQUAL_CONST) != 0);
    bool isUnmasked = ((typeQualifiers & TYPEQUAL_UNMASKED) != 0);

    if (hasUniformQual && hasVaryingQual) {
        Error(pos, "Can't provide both \"uniform\" and \"varying\" qualifiers.");
        return;
    }
    if (kind != DK_FUNCTION && isTask) {
        Error(pos, "\"task\" qualifier illegal in variable declaration.");
        return;
    }
    if (kind != DK_FUNCTION && isUnmasked) {
        Error(pos, "\"unmasked\" qualifier illegal in variable declaration.");
        return;
    }
    if (kind != DK_FUNCTION && isExported) {
        Error(pos, "\"export\" qualifier illegal in variable declaration.");
        return;
    }

    Variability variability(Variability::Unbound);
    if (hasUniformQual)
        variability = Variability::Uniform;
    else if (hasVaryingQual)
        variability = Variability::Varying;

    if (kind == DK_BASE) {
        // All of the type qualifiers should be in the DeclSpecs for the
        // base declarator
        AssertPos(pos, typeQualifiers == 0);
        AssertPos(pos, child == NULL);
        type = baseType;
    } else if (kind == DK_POINTER) {
        /* For now, any pointer to an SOA type gets the slice property; if
           we add the capability to declare pointers as slices or not,
           we'll want to set this based on a type qualifier here. */
        const Type *ptrType = new PointerType(baseType, variability, isConst, baseType->IsSOAType());
        if (child != NULL) {
            child->InitFromType(ptrType, ds);
            type = child->type;
            name = child->name;
        } else
            type = ptrType;
    } else if (kind == DK_REFERENCE) {
        if (hasUniformQual) {
            Error(pos, "\"uniform\" qualifier is illegal to apply to references.");
            return;
        }
        if (hasVaryingQual) {
            Error(pos, "\"varying\" qualifier is illegal to apply to references.");
            return;
        }
        if (isConst) {
            Error(pos, "\"const\" qualifier is to illegal apply to references.");
            return;
        }
        // The parser should disallow this already, but double check.
        if (CastType<ReferenceType>(baseType) != NULL) {
            Error(pos, "References to references are illegal.");
            return;
        }

        const Type *refType = new ReferenceType(baseType);
        if (child != NULL) {
            child->InitFromType(refType, ds);
            type = child->type;
            name = child->name;
        } else
            type = refType;
    } else if (kind == DK_ARRAY) {
        if (baseType->IsVoidType()) {
            Error(pos, "Arrays of \"void\" type are illegal.");
            return;
        }
        if (CastType<ReferenceType>(baseType)) {
            Error(pos, "Arrays of references (type \"%s\") are illegal.", baseType->GetString().c_str());
            return;
        }

        const Type *arrayType = new ArrayType(baseType, arraySize);
        if (child != NULL) {
            child->InitFromType(arrayType, ds);
            type = child->type;
            name = child->name;
        } else {
            type = arrayType;
        }
    } else if (kind == DK_FUNCTION) {
        llvm::SmallVector<const Type *, 8> args;
        llvm::SmallVector<std::string, 8> argNames;
        llvm::SmallVector<Expr *, 8> argDefaults;
        llvm::SmallVector<SourcePos, 8> argPos;

        // Loop over the function arguments and store the names, types,
        // default values (if any), and source file positions each one in
        // the corresponding vector.
        for (unsigned int i = 0; i < functionParams.size(); ++i) {
            Declaration *d = functionParams[i];

            if (d == NULL) {
                AssertPos(pos, m->errorCount > 0);
                continue;
            }
            if (d->declarators.size() == 0) {
                // function declaration like foo(float), w/o a name for the
                // parameter; wire up a placeholder Declarator for it
                d->declarators.push_back(new Declarator(DK_BASE, pos));
                d->declarators[0]->InitFromDeclSpecs(d->declSpecs);
            }

            AssertPos(pos, d->declarators.size() == 1);
            Declarator *decl = d->declarators[0];
            if (decl == NULL || decl->type == NULL) {
                AssertPos(pos, m->errorCount > 0);
                continue;
            }

            if (decl->name == "") {
                // Give a name to any anonymous parameter declarations
                char buf[32];
                snprintf(buf, sizeof(buf), "__anon_parameter_%d", i);
                decl->name = buf;
            }
            decl->type = decl->type->ResolveUnboundVariability(Variability::Varying);

            if (d->declSpecs->storageClass != SC_NONE)
                Error(decl->pos,
                      "Storage class \"%s\" is illegal in "
                      "function parameter declaration for parameter \"%s\".",
                      lGetStorageClassName(d->declSpecs->storageClass), decl->name.c_str());
            if (decl->type->IsVoidType()) {
                Error(decl->pos, "Parameter with type \"void\" illegal in function "
                                 "parameter list.");
                decl->type = NULL;
            }

            const ArrayType *at = CastType<ArrayType>(decl->type);
            if (at != NULL) {
                // As in C, arrays are passed to functions as pointers to
                // their element type.  We'll just immediately make this
                // change now.  (One shortcoming of losing the fact that
                // the it was originally an array is that any warnings or
                // errors later issued that print the function type will
                // report this differently than it was originally declared
                // in the function, but it's not clear that this is a
                // significant problem.)
                const Type *targetType = at->GetElementType();
                if (targetType == NULL) {
                    AssertPos(pos, m->errorCount > 0);
                    return;
                }

                decl->type = PointerType::GetUniform(targetType, at->IsSOAType());

                // Make sure there are no unsized arrays (other than the
                // first dimension) in function parameter lists.
                at = CastType<ArrayType>(targetType);
                while (at != NULL) {
                    if (at->GetElementCount() == 0)
                        Error(decl->pos, "Arrays with unsized dimensions in "
                                         "dimensions after the first one are illegal in "
                                         "function parameter lists.");
                    at = CastType<ArrayType>(at->GetElementType());
                }
            }

            args.push_back(decl->type);
            argNames.push_back(decl->name);
            argPos.push_back(decl->pos);

            Expr *init = NULL;
            // Try to find an initializer expression.
            while (decl != NULL) {
                if (decl->initExpr != NULL) {
                    decl->initExpr = TypeCheck(decl->initExpr);
                    decl->initExpr = Optimize(decl->initExpr);
                    if (decl->initExpr != NULL) {
                        init = llvm::dyn_cast<ConstExpr>(decl->initExpr);
                        if (init == NULL)
                            init = llvm::dyn_cast<NullPointerExpr>(decl->initExpr);
                        if (init == NULL)
                            Error(decl->initExpr->pos,
                                  "Default value for parameter "
                                  "\"%s\" must be a compile-time constant.",
                                  decl->name.c_str());
                    }
                    break;
                } else
                    decl = decl->child;
            }
            argDefaults.push_back(init);
        }

        const Type *returnType = baseType;
        if (returnType == NULL) {
            Error(pos, "No return type provided in function declaration.");
            return;
        }

        if (CastType<FunctionType>(returnType) != NULL) {
            Error(pos, "Illegal to return function type from function.");
            return;
        }

        returnType = returnType->ResolveUnboundVariability(Variability::Varying);

        bool isExternC = ds && (ds->storageClass == SC_EXTERN_C);
        bool isExported = ds && ((ds->typeQualifiers & TYPEQUAL_EXPORT) != 0);
        bool isTask = ds && ((ds->typeQualifiers & TYPEQUAL_TASK) != 0);
        bool isUnmasked = ds && ((ds->typeQualifiers & TYPEQUAL_UNMASKED) != 0);

        if (isExported && isTask) {
            Error(pos, "Function can't have both \"task\" and \"export\" "
                       "qualifiers");
            return;
        }
        if (isExternC && isTask) {
            Error(pos, "Function can't have both \"extern \"C\"\" and \"task\" "
                       "qualifiers");
            return;
        }
        if (isExternC && isExported) {
            Error(pos, "Function can't have both \"extern \"C\"\" and \"export\" "
                       "qualifiers");
            return;
        }
        if (isUnmasked && isExported)
            Warning(pos, "\"unmasked\" qualifier is redundant for exported "
                         "functions.");

        if (child == NULL) {
            AssertPos(pos, m->errorCount > 0);
            return;
        }

        const FunctionType *functionType = new FunctionType(returnType, args, argNames, argDefaults, argPos, isTask,
                                                            isExported, isExternC, isUnmasked);

        // handle any explicit __declspecs on the function
        if (ds != NULL) {
            for (int i = 0; i < (int)ds->declSpecList.size(); ++i) {
                std::string str = ds->declSpecList[i].first;
                SourcePos ds_spec_pos = ds->declSpecList[i].second;

                if (str == "safe")
                    (const_cast<FunctionType *>(functionType))->isSafe = true;
                else if (!strncmp(str.c_str(), "cost", 4)) {
                    int cost = atoi(str.c_str() + 4);
                    if (cost < 0)
                        Error(ds_spec_pos, "Negative function cost %d is illegal.", cost);
                    (const_cast<FunctionType *>(functionType))->costOverride = cost;
                } else
                    Error(ds_spec_pos, "__declspec parameter \"%s\" unknown.", str.c_str());
            }
        }

        child->InitFromType(functionType, ds);
        type = child->type;
        name = child->name;
    }
}

///////////////////////////////////////////////////////////////////////////
// Declaration

Declaration::Declaration(DeclSpecs *ds, std::vector<Declarator *> *dlist) {
    declSpecs = ds;
    if (dlist != NULL)
        declarators = *dlist;
    for (unsigned int i = 0; i < declarators.size(); ++i)
        if (declarators[i] != NULL)
            declarators[i]->InitFromDeclSpecs(declSpecs);
}

Declaration::Declaration(DeclSpecs *ds, Declarator *d) {
    declSpecs = ds;
    if (d != NULL) {
        d->InitFromDeclSpecs(ds);
        declarators.push_back(d);
    }
}

std::vector<VariableDeclaration> Declaration::GetVariableDeclarations() const {
    Assert(declSpecs->storageClass != SC_TYPEDEF);
    std::vector<VariableDeclaration> vars;

    for (unsigned int i = 0; i < declarators.size(); ++i) {
        Declarator *decl = declarators[i];
        if (decl == NULL || decl->type == NULL) {
            // Ignore earlier errors
            Assert(m->errorCount > 0);
            continue;
        }

        if (decl->type->IsVoidType())
            Error(decl->pos, "\"void\" type variable illegal in declaration.");
        else if (CastType<FunctionType>(decl->type) == NULL) {
            decl->type = decl->type->ResolveUnboundVariability(Variability::Varying);
            Symbol *sym = new Symbol(decl->name, decl->pos, decl->type, decl->storageClass);
            m->symbolTable->AddVariable(sym);
            vars.push_back(VariableDeclaration(sym, decl->initExpr));
        }
    }

    return vars;
}

void Declaration::DeclareFunctions() {
    Assert(declSpecs->storageClass != SC_TYPEDEF);

    for (unsigned int i = 0; i < declarators.size(); ++i) {
        Declarator *decl = declarators[i];
        if (decl == NULL || decl->type == NULL) {
            // Ignore earlier errors
            Assert(m->errorCount > 0);
            continue;
        }

        const FunctionType *ftype = CastType<FunctionType>(decl->type);
        if (ftype == NULL)
            continue;

        bool isInline = (declSpecs->typeQualifiers & TYPEQUAL_INLINE);
        bool isNoInline = (declSpecs->typeQualifiers & TYPEQUAL_NOINLINE);
        bool isVectorCall = (declSpecs->typeQualifiers & TYPEQUAL_VECTORCALL);
        m->AddFunctionDeclaration(decl->name, ftype, decl->storageClass, isInline, isNoInline, isVectorCall, decl->pos);
    }
}

void Declaration::Print(int indent) const {
    printf("%*cDeclaration: specs [", indent, ' ');
    declSpecs->Print();
    printf("], declarators:\n");
    for (unsigned int i = 0; i < declarators.size(); ++i)
        declarators[i]->Print(indent + 4);
}

///////////////////////////////////////////////////////////////////////////

void ispc::GetStructTypesNamesPositions(const std::vector<StructDeclaration *> &sd,
                                        llvm::SmallVector<const Type *, 8> *elementTypes,
                                        llvm::SmallVector<std::string, 8> *elementNames,
                                        llvm::SmallVector<SourcePos, 8> *elementPositions) {
    std::set<std::string> seenNames;
    for (unsigned int i = 0; i < sd.size(); ++i) {
        const Type *type = sd[i]->type;
        if (type == NULL)
            continue;

        // FIXME: making this fake little DeclSpecs here is really
        // disgusting
        DeclSpecs ds(type);
        if (type->IsVoidType() == false) {
            if (type->IsUniformType())
                ds.typeQualifiers |= TYPEQUAL_UNIFORM;
            else if (type->IsVaryingType())
                ds.typeQualifiers |= TYPEQUAL_VARYING;
            else if (type->GetSOAWidth() != 0)
                ds.soaWidth = type->GetSOAWidth();
            // FIXME: ds.vectorSize?
        }

        for (unsigned int j = 0; j < sd[i]->declarators->size(); ++j) {
            Declarator *d = (*sd[i]->declarators)[j];
            d->InitFromDeclSpecs(&ds);

            if (d->type->IsVoidType())
                Error(d->pos, "\"void\" type illegal for struct member.");

            elementTypes->push_back(d->type);

            if (seenNames.find(d->name) != seenNames.end())
                Error(d->pos,
                      "Struct member \"%s\" has same name as a "
                      "previously-declared member.",
                      d->name.c_str());
            else
                seenNames.insert(d->name);

            elementNames->push_back(d->name);
            elementPositions->push_back(d->pos);
        }
    }

    for (int i = 0; i < (int)elementTypes->size() - 1; ++i) {
        const ArrayType *arrayType = CastType<ArrayType>((*elementTypes)[i]);

        if (arrayType != NULL && arrayType->GetElementCount() == 0)
            Error((*elementPositions)[i], "Unsized arrays aren't allowed except "
                                          "for the last member in a struct definition.");
    }
}