flang/runtime/assign.cpp

   1 //===-- runtime/assign.cpp ------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "flang/Runtime/assign.h"
  10 #include "assign-impl.h"
  11 #include "derived.h"
  12 #include "stat.h"
  13 #include "terminator.h"
  14 #include "tools.h"
  15 #include "type-info.h"
  16 #include "flang/Runtime/descriptor.h"
  17
  18 namespace Fortran::runtime {
  19
  20 enum AssignFlags {
  21   NoAssignFlags = 0,
  22   MaybeReallocate = 1 << 0,
  23   NeedFinalization = 1 << 1,
  24   CanBeDefinedAssignment = 1 << 2,
  25   ComponentCanBeDefinedAssignment = 1 << 3,
  26   ExplicitLengthCharacterLHS = 1 << 4,
  27   PolymorphicLHS = 1 << 5,
  28   DeallocateLHS = 1 << 6
  29 };
  30
  31 // Predicate: is the left-hand side of an assignment an allocated allocatable
  32 // that must be deallocated?
  33 static inline RT_API_ATTRS bool MustDeallocateLHS(
  34     Descriptor &to, const Descriptor &from, Terminator &terminator, int flags) {
  35   // Top-level assignments to allocatable variables (*not* components)
  36   // may first deallocate existing content if there's about to be a
  37   // change in type or shape; see F'2018 10.2.1.3(3).
  38   if (!(flags & MaybeReallocate)) {
  39     return false;
  40   }
  41   if (!to.IsAllocatable() || !to.IsAllocated()) {
  42     return false;
  43   }
  44   if (to.type() != from.type()) {
  45     return true;
  46   }
  47   if (!(flags & ExplicitLengthCharacterLHS) && to.type().IsCharacter() &&
  48       to.ElementBytes() != from.ElementBytes()) {
  49     return true;
  50   }
  51   if (flags & PolymorphicLHS) {
  52     DescriptorAddendum *toAddendum{to.Addendum()};
  53     const typeInfo::DerivedType *toDerived{
  54         toAddendum ? toAddendum->derivedType() : nullptr};
  55     const DescriptorAddendum *fromAddendum{from.Addendum()};
  56     const typeInfo::DerivedType *fromDerived{
  57         fromAddendum ? fromAddendum->derivedType() : nullptr};
  58     if (toDerived != fromDerived) {
  59       return true;
  60     }
  61     if (fromDerived) {
  62       // Distinct LEN parameters? Deallocate
  63       std::size_t lenParms{fromDerived->LenParameters()};
  64       for (std::size_t j{0}; j < lenParms; ++j) {
  65         if (toAddendum->LenParameterValue(j) !=
  66             fromAddendum->LenParameterValue(j)) {
  67           return true;
  68         }
  69       }
  70     }
  71   }
  72   if (from.rank() > 0) {
  73     // Distinct shape? Deallocate
  74     int rank{to.rank()};
  75     for (int j{0}; j < rank; ++j) {
  76       if (to.GetDimension(j).Extent() != from.GetDimension(j).Extent()) {
  77         return true;
  78       }
  79     }
  80   }
  81   return false;
  82 }
  83
  84 // Utility: allocate the allocatable left-hand side, either because it was
  85 // originally deallocated or because it required reallocation
  86 static RT_API_ATTRS int AllocateAssignmentLHS(
  87     Descriptor &to, const Descriptor &from, Terminator &terminator, int flags) {
  88   to.raw().type = from.raw().type;
  89   if (!(flags & ExplicitLengthCharacterLHS)) {
  90     to.raw().elem_len = from.ElementBytes();
  91   }
  92   const typeInfo::DerivedType *derived{nullptr};
  93   if (const DescriptorAddendum * fromAddendum{from.Addendum()}) {
  94     derived = fromAddendum->derivedType();
  95     if (DescriptorAddendum * toAddendum{to.Addendum()}) {
  96       toAddendum->set_derivedType(derived);
  97       std::size_t lenParms{derived ? derived->LenParameters() : 0};
  98       for (std::size_t j{0}; j < lenParms; ++j) {
  99         toAddendum->SetLenParameterValue(j, fromAddendum->LenParameterValue(j));
 100       }
 101     }
 102   }
 103   // subtle: leave bounds in place when "from" is scalar (10.2.1.3(3))
 104   int rank{from.rank()};
 105   auto stride{static_cast<SubscriptValue>(to.ElementBytes())};
 106   for (int j{0}; j < rank; ++j) {
 107     auto &toDim{to.GetDimension(j)};
 108     const auto &fromDim{from.GetDimension(j)};
 109     toDim.SetBounds(fromDim.LowerBound(), fromDim.UpperBound());
 110     toDim.SetByteStride(stride);
 111     stride *= toDim.Extent();
 112   }
 113   int result{ReturnError(terminator, to.Allocate())};
 114   if (result == StatOk && derived && !derived->noInitializationNeeded()) {
 115     result = ReturnError(terminator, Initialize(to, *derived, terminator));
 116   }
 117   return result;
 118 }
 119
 120 // least <= 0, most >= 0
 121 static RT_API_ATTRS void MaximalByteOffsetRange(
 122     const Descriptor &desc, std::int64_t &least, std::int64_t &most) {
 123   least = most = 0;
 124   if (desc.ElementBytes() == 0) {
 125     return;
 126   }
 127   int n{desc.raw().rank};
 128   for (int j{0}; j < n; ++j) {
 129     const auto &dim{desc.GetDimension(j)};
 130     auto extent{dim.Extent()};
 131     if (extent > 0) {
 132       auto sm{dim.ByteStride()};
 133       if (sm < 0) {
 134         least += (extent - 1) * sm;
 135       } else {
 136         most += (extent - 1) * sm;
 137       }
 138     }
 139   }
 140   most += desc.ElementBytes() - 1;
 141 }
 142
 143 static inline RT_API_ATTRS bool RangesOverlap(const char *aStart,
 144     const char *aEnd, const char *bStart, const char *bEnd) {
 145   return aEnd >= bStart && bEnd >= aStart;
 146 }
 147
 148 // Predicate: could the left-hand and right-hand sides of the assignment
 149 // possibly overlap in memory?  Note that the descriptors themeselves
 150 // are included in the test.
 151 static RT_API_ATTRS bool MayAlias(const Descriptor &x, const Descriptor &y) {
 152   const char *xBase{x.OffsetElement()};
 153   const char *yBase{y.OffsetElement()};
 154   if (!xBase || !yBase) {
 155     return false; // not both allocated
 156   }
 157   const char *xDesc{reinterpret_cast<const char *>(&x)};
 158   const char *xDescLast{xDesc + x.SizeInBytes()};
 159   const char *yDesc{reinterpret_cast<const char *>(&y)};
 160   const char *yDescLast{yDesc + y.SizeInBytes()};
 161   std::int64_t xLeast, xMost, yLeast, yMost;
 162   MaximalByteOffsetRange(x, xLeast, xMost);
 163   MaximalByteOffsetRange(y, yLeast, yMost);
 164   if (RangesOverlap(xDesc, xDescLast, yBase + yLeast, yBase + yMost) ||
 165       RangesOverlap(yDesc, yDescLast, xBase + xLeast, xBase + xMost)) {
 166     // A descriptor overlaps with the storage described by the other;
 167     // this can arise when an allocatable or pointer component is
 168     // being assigned to/from.
 169     return true;
 170   }
 171   if (!RangesOverlap(
 172           xBase + xLeast, xBase + xMost, yBase + yLeast, yBase + yMost)) {
 173     return false; // no storage overlap
 174   }
 175   // TODO: check dimensions: if any is independent, return false
 176   return true;
 177 }
 178
 179 static RT_API_ATTRS void DoScalarDefinedAssignment(const Descriptor &to,
 180     const Descriptor &from, const typeInfo::SpecialBinding &special) {
 181   bool toIsDesc{special.IsArgDescriptor(0)};
 182   bool fromIsDesc{special.IsArgDescriptor(1)};
 183   if (toIsDesc) {
 184     if (fromIsDesc) {
 185       auto *p{
 186           special.GetProc<void (*)(const Descriptor &, const Descriptor &)>()};
 187       p(to, from);
 188     } else {
 189       auto *p{special.GetProc<void (*)(const Descriptor &, void *)>()};
 190       p(to, from.raw().base_addr);
 191     }
 192   } else {
 193     if (fromIsDesc) {
 194       auto *p{special.GetProc<void (*)(void *, const Descriptor &)>()};
 195       p(to.raw().base_addr, from);
 196     } else {
 197       auto *p{special.GetProc<void (*)(void *, void *)>()};
 198       p(to.raw().base_addr, from.raw().base_addr);
 199     }
 200   }
 201 }
 202
 203 static RT_API_ATTRS void DoElementalDefinedAssignment(const Descriptor &to,
 204     const Descriptor &from, const typeInfo::DerivedType &derived,
 205     const typeInfo::SpecialBinding &special) {
 206   SubscriptValue toAt[maxRank], fromAt[maxRank];
 207   to.GetLowerBounds(toAt);
 208   from.GetLowerBounds(fromAt);
 209   StaticDescriptor<maxRank, true, 8 /*?*/> statDesc[2];
 210   Descriptor &toElementDesc{statDesc[0].descriptor()};
 211   Descriptor &fromElementDesc{statDesc[1].descriptor()};
 212   toElementDesc.Establish(derived, nullptr, 0, nullptr, CFI_attribute_pointer);
 213   fromElementDesc.Establish(
 214       derived, nullptr, 0, nullptr, CFI_attribute_pointer);
 215   for (std::size_t toElements{to.Elements()}; toElements-- > 0;
 216        to.IncrementSubscripts(toAt), from.IncrementSubscripts(fromAt)) {
 217     toElementDesc.set_base_addr(to.Element<char>(toAt));
 218     fromElementDesc.set_base_addr(from.Element<char>(fromAt));
 219     DoScalarDefinedAssignment(toElementDesc, fromElementDesc, special);
 220   }
 221 }
 222
 223 template <typename CHAR>
 224 static RT_API_ATTRS void BlankPadCharacterAssignment(Descriptor &to,
 225     const Descriptor &from, SubscriptValue toAt[], SubscriptValue fromAt[],
 226     std::size_t elements, std::size_t toElementBytes,
 227     std::size_t fromElementBytes) {
 228   std::size_t padding{(toElementBytes - fromElementBytes) / sizeof(CHAR)};
 229   std::size_t copiedCharacters{fromElementBytes / sizeof(CHAR)};
 230   for (; elements-- > 0;
 231        to.IncrementSubscripts(toAt), from.IncrementSubscripts(fromAt)) {
 232     CHAR *p{to.Element<CHAR>(toAt)};
 233     Fortran::runtime::memmove(
 234         p, from.Element<std::add_const_t<CHAR>>(fromAt), fromElementBytes);
 235     p += copiedCharacters;
 236     for (auto n{padding}; n-- > 0;) {
 237       *p++ = CHAR{' '};
 238     }
 239   }
 240 }
 241
 242 // Common implementation of assignments, both intrinsic assignments and
 243 // those cases of polymorphic user-defined ASSIGNMENT(=) TBPs that could not
 244 // be resolved in semantics.  Most assignment statements do not need any
 245 // of the capabilities of this function -- but when the LHS is allocatable,
 246 // the type might have a user-defined ASSIGNMENT(=), or the type might be
 247 // finalizable, this function should be used.
 248 // When "to" is not a whole allocatable, "from" is an array, and defined
 249 // assignments are not used, "to" and "from" only need to have the same number
 250 // of elements, but their shape need not to conform (the assignment is done in
 251 // element sequence order). This facilitates some internal usages, like when
 252 // dealing with array constructors.
 253 RT_API_ATTRS static void Assign(
 254     Descriptor &to, const Descriptor &from, Terminator &terminator, int flags) {
 255   bool mustDeallocateLHS{(flags & DeallocateLHS) ||
 256       MustDeallocateLHS(to, from, terminator, flags)};
 257   DescriptorAddendum *toAddendum{to.Addendum()};
 258   const typeInfo::DerivedType *toDerived{
 259       toAddendum ? toAddendum->derivedType() : nullptr};
 260   if (toDerived && (flags & NeedFinalization) &&
 261       toDerived->noFinalizationNeeded()) {
 262     flags &= ~NeedFinalization;
 263   }
 264   std::size_t toElementBytes{to.ElementBytes()};
 265   std::size_t fromElementBytes{from.ElementBytes()};
 266   // The following lambda definition violates the conding style,
 267   // but cuda-11.8 nvcc hits an internal error with the brace initialization.
 268   auto isSimpleMemmove = [&]() {
 269     return !toDerived && to.rank() == from.rank() && to.IsContiguous() &&
 270         from.IsContiguous() && toElementBytes == fromElementBytes;
 271   };
 272   StaticDescriptor<maxRank, true, 10 /*?*/> deferredDeallocStatDesc;
 273   Descriptor *deferDeallocation{nullptr};
 274   if (MayAlias(to, from)) {
 275     if (mustDeallocateLHS) {
 276       deferDeallocation = &deferredDeallocStatDesc.descriptor();
 277       std::memcpy(deferDeallocation, &to, to.SizeInBytes());
 278       to.set_base_addr(nullptr);
 279     } else if (!isSimpleMemmove()) {
 280       // Handle LHS/RHS aliasing by copying RHS into a temp, then
 281       // recursively assigning from that temp.
 282       auto descBytes{from.SizeInBytes()};
 283       StaticDescriptor<maxRank, true, 16> staticDesc;
 284       Descriptor &newFrom{staticDesc.descriptor()};
 285       std::memcpy(&newFrom, &from, descBytes);
 286       // Pretend the temporary descriptor is for an ALLOCATABLE
 287       // entity, otherwise, the Deallocate() below will not
 288       // free the descriptor memory.
 289       newFrom.raw().attribute = CFI_attribute_allocatable;
 290       auto stat{ReturnError(terminator, newFrom.Allocate())};
 291       if (stat == StatOk) {
 292         if (HasDynamicComponent(from)) {
 293           // If 'from' has allocatable/automatic component, we cannot
 294           // just make a shallow copy of the descriptor member.
 295           // This will still leave data overlap in 'to' and 'newFrom'.
 296           // For example:
 297           //   type t
 298           //     character, allocatable :: c(:)
 299           //   end type t
 300           //   type(t) :: x(3)
 301           //   x(2:3) = x(1:2)
 302           // We have to make a deep copy into 'newFrom' in this case.
 303           RTNAME(AssignTemporary)
 304           (newFrom, from, terminator.sourceFileName(), terminator.sourceLine());
 305         } else {
 306           ShallowCopy(newFrom, from, true, from.IsContiguous());
 307         }
 308         Assign(to, newFrom, terminator,
 309             flags &
 310                 (NeedFinalization | ComponentCanBeDefinedAssignment |
 311                     ExplicitLengthCharacterLHS | CanBeDefinedAssignment));
 312         newFrom.Deallocate();
 313       }
 314       return;
 315     }
 316   }
 317   if (to.IsAllocatable()) {
 318     if (mustDeallocateLHS) {
 319       if (deferDeallocation) {
 320         if ((flags & NeedFinalization) && toDerived) {
 321           Finalize(to, *toDerived, &terminator);
 322           flags &= ~NeedFinalization;
 323         } else if (toDerived && !toDerived->noDestructionNeeded()) {
 324           Destroy(to, /*finalize=*/false, *toDerived, &terminator);
 325         }
 326       } else {
 327         to.Destroy((flags & NeedFinalization) != 0, /*destroyPointers=*/false,
 328             &terminator);
 329         flags &= ~NeedFinalization;
 330       }
 331     } else if (to.rank() != from.rank() && !to.IsAllocated()) {
 332       terminator.Crash("Assign: mismatched ranks (%d != %d) in assignment to "
 333                        "unallocated allocatable",
 334           to.rank(), from.rank());
 335     }
 336     if (!to.IsAllocated()) {
 337       if (AllocateAssignmentLHS(to, from, terminator, flags) != StatOk) {
 338         return;
 339       }
 340       flags &= ~NeedFinalization;
 341       toElementBytes = to.ElementBytes(); // may have changed
 342     }
 343   }
 344   if (toDerived && (flags & CanBeDefinedAssignment)) {
 345     // Check for a user-defined assignment type-bound procedure;
 346     // see 10.2.1.4-5.  A user-defined assignment TBP defines all of
 347     // the semantics, including allocatable (re)allocation and any
 348     // finalization.
 349     //
 350     // Note that the aliasing and LHS (re)allocation handling above
 351     // needs to run even with CanBeDefinedAssignment flag, when
 352     // the Assign() is invoked recursively for component-per-component
 353     // assignments.
 354     if (to.rank() == 0) {
 355       if (const auto *special{toDerived->FindSpecialBinding(
 356               typeInfo::SpecialBinding::Which::ScalarAssignment)}) {
 357         return DoScalarDefinedAssignment(to, from, *special);
 358       }
 359     }
 360     if (const auto *special{toDerived->FindSpecialBinding(
 361             typeInfo::SpecialBinding::Which::ElementalAssignment)}) {
 362       return DoElementalDefinedAssignment(to, from, *toDerived, *special);
 363     }
 364   }
 365   SubscriptValue toAt[maxRank];
 366   to.GetLowerBounds(toAt);
 367   // Scalar expansion of the RHS is implied by using the same empty
 368   // subscript values on each (seemingly) elemental reference into
 369   // "from".
 370   SubscriptValue fromAt[maxRank];
 371   from.GetLowerBounds(fromAt);
 372   std::size_t toElements{to.Elements()};
 373   if (from.rank() > 0 && toElements != from.Elements()) {
 374     terminator.Crash("Assign: mismatching element counts in array assignment "
 375                      "(to %zd, from %zd)",
 376         toElements, from.Elements());
 377   }
 378   if (to.type() != from.type()) {
 379     terminator.Crash("Assign: mismatching types (to code %d != from code %d)",
 380         to.type().raw(), from.type().raw());
 381   }
 382   if (toElementBytes > fromElementBytes && !to.type().IsCharacter()) {
 383     terminator.Crash("Assign: mismatching non-character element sizes (to %zd "
 384                      "bytes != from %zd bytes)",
 385         toElementBytes, fromElementBytes);
 386   }
 387   if (const typeInfo::DerivedType *
 388       updatedToDerived{toAddendum ? toAddendum->derivedType() : nullptr}) {
 389     // Derived type intrinsic assignment, which is componentwise and elementwise
 390     // for all components, including parent components (10.2.1.2-3).
 391     // The target is first finalized if still necessary (7.5.6.3(1))
 392     if (flags & NeedFinalization) {
 393       Finalize(to, *updatedToDerived, &terminator);
 394     } else if (updatedToDerived && !updatedToDerived->noDestructionNeeded()) {
 395       Destroy(to, /*finalize=*/false, *updatedToDerived, &terminator);
 396     }
 397     // Copy the data components (incl. the parent) first.
 398     const Descriptor &componentDesc{updatedToDerived->component()};
 399     std::size_t numComponents{componentDesc.Elements()};
 400     for (std::size_t j{0}; j < toElements;
 401          ++j, to.IncrementSubscripts(toAt), from.IncrementSubscripts(fromAt)) {
 402       for (std::size_t k{0}; k < numComponents; ++k) {
 403         const auto &comp{
 404             *componentDesc.ZeroBasedIndexedElement<typeInfo::Component>(
 405                 k)}; // TODO: exploit contiguity here
 406         // Use PolymorphicLHS for components so that the right things happen
 407         // when the components are polymorphic; when they're not, they're both
 408         // not, and their declared types will match.
 409         int nestedFlags{MaybeReallocate | PolymorphicLHS};
 410         if (flags & ComponentCanBeDefinedAssignment) {
 411           nestedFlags |=
 412               CanBeDefinedAssignment | ComponentCanBeDefinedAssignment;
 413         }
 414         switch (comp.genre()) {
 415         case typeInfo::Component::Genre::Data:
 416           if (comp.category() == TypeCategory::Derived) {
 417             StaticDescriptor<maxRank, true, 10 /*?*/> statDesc[2];
 418             Descriptor &toCompDesc{statDesc[0].descriptor()};
 419             Descriptor &fromCompDesc{statDesc[1].descriptor()};
 420             comp.CreatePointerDescriptor(toCompDesc, to, terminator, toAt);
 421             comp.CreatePointerDescriptor(
 422                 fromCompDesc, from, terminator, fromAt);
 423             Assign(toCompDesc, fromCompDesc, terminator, nestedFlags);
 424           } else { // Component has intrinsic type; simply copy raw bytes
 425             std::size_t componentByteSize{comp.SizeInBytes(to)};
 426             Fortran::runtime::memmove(to.Element<char>(toAt) + comp.offset(),
 427                 from.Element<const char>(fromAt) + comp.offset(),
 428                 componentByteSize);
 429           }
 430           break;
 431         case typeInfo::Component::Genre::Pointer: {
 432           std::size_t componentByteSize{comp.SizeInBytes(to)};
 433           Fortran::runtime::memmove(to.Element<char>(toAt) + comp.offset(),
 434               from.Element<const char>(fromAt) + comp.offset(),
 435               componentByteSize);
 436         } break;
 437         case typeInfo::Component::Genre::Allocatable:
 438         case typeInfo::Component::Genre::Automatic: {
 439           auto *toDesc{reinterpret_cast<Descriptor *>(
 440               to.Element<char>(toAt) + comp.offset())};
 441           const auto *fromDesc{reinterpret_cast<const Descriptor *>(
 442               from.Element<char>(fromAt) + comp.offset())};
 443           // Allocatable components of the LHS are unconditionally
 444           // deallocated before assignment (F'2018 10.2.1.3(13)(1)),
 445           // unlike a "top-level" assignment to a variable, where
 446           // deallocation is optional.
 447           //
 448           // Be careful not to destroy/reallocate the LHS, if there is
 449           // overlap between LHS and RHS (it seems that partial overlap
 450           // is not possible, though).
 451           // Invoke Assign() recursively to deal with potential aliasing.
 452           if (toDesc->IsAllocatable()) {
 453             if (!fromDesc->IsAllocated()) {
 454               // No aliasing.
 455               //
 456               // If to is not allocated, the Destroy() call is a no-op.
 457               // This is just a shortcut, because the recursive Assign()
 458               // below would initiate the destruction for to.
 459               // No finalization is required.
 460               toDesc->Destroy(
 461                   /*finalize=*/false, /*destroyPointers=*/false, &terminator);
 462               continue; // F'2018 10.2.1.3(13)(2)
 463             }
 464           }
 465           // Force LHS deallocation with DeallocateLHS flag.
 466           // The actual deallocation may be avoided, if the existing
 467           // location can be reoccupied.
 468           Assign(*toDesc, *fromDesc, terminator, nestedFlags | DeallocateLHS);
 469         } break;
 470         }
 471       }
 472       // Copy procedure pointer components
 473       const Descriptor &procPtrDesc{updatedToDerived->procPtr()};
 474       std::size_t numProcPtrs{procPtrDesc.Elements()};
 475       for (std::size_t k{0}; k < numProcPtrs; ++k) {
 476         const auto &procPtr{
 477             *procPtrDesc.ZeroBasedIndexedElement<typeInfo::ProcPtrComponent>(
 478                 k)};
 479         Fortran::runtime::memmove(to.Element<char>(toAt) + procPtr.offset,
 480             from.Element<const char>(fromAt) + procPtr.offset,
 481             sizeof(typeInfo::ProcedurePointer));
 482       }
 483     }
 484   } else { // intrinsic type, intrinsic assignment
 485     if (isSimpleMemmove()) {
 486       Fortran::runtime::memmove(to.raw().base_addr, from.raw().base_addr,
 487           toElements * toElementBytes);
 488     } else if (toElementBytes > fromElementBytes) { // blank padding
 489       switch (to.type().raw()) {
 490       case CFI_type_signed_char:
 491       case CFI_type_char:
 492         BlankPadCharacterAssignment<char>(to, from, toAt, fromAt, toElements,
 493             toElementBytes, fromElementBytes);
 494         break;
 495       case CFI_type_char16_t:
 496         BlankPadCharacterAssignment<char16_t>(to, from, toAt, fromAt,
 497             toElements, toElementBytes, fromElementBytes);
 498         break;
 499       case CFI_type_char32_t:
 500         BlankPadCharacterAssignment<char32_t>(to, from, toAt, fromAt,
 501             toElements, toElementBytes, fromElementBytes);
 502         break;
 503       default:
 504         terminator.Crash("unexpected type code %d in blank padded Assign()",
 505             to.type().raw());
 506       }
 507     } else { // elemental copies, possibly with character truncation
 508       for (std::size_t n{toElements}; n-- > 0;
 509            to.IncrementSubscripts(toAt), from.IncrementSubscripts(fromAt)) {
 510         Fortran::runtime::memmove(to.Element<char>(toAt),
 511             from.Element<const char>(fromAt), toElementBytes);
 512       }
 513     }
 514   }
 515   if (deferDeallocation) {
 516     // deferDeallocation is used only when LHS is an allocatable.
 517     // The finalization has already been run for it.
 518     deferDeallocation->Destroy(
 519         /*finalize=*/false, /*destroyPointers=*/false, &terminator);
 520   }
 521 }
 522
 523 RT_OFFLOAD_API_GROUP_BEGIN
 524
 525 RT_API_ATTRS void DoFromSourceAssign(
 526     Descriptor &alloc, const Descriptor &source, Terminator &terminator) {
 527   if (alloc.rank() > 0 && source.rank() == 0) {
 528     // The value of each element of allocate object becomes the value of source.
 529     DescriptorAddendum *allocAddendum{alloc.Addendum()};
 530     const typeInfo::DerivedType *allocDerived{
 531         allocAddendum ? allocAddendum->derivedType() : nullptr};
 532     SubscriptValue allocAt[maxRank];
 533     alloc.GetLowerBounds(allocAt);
 534     if (allocDerived) {
 535       for (std::size_t n{alloc.Elements()}; n-- > 0;
 536            alloc.IncrementSubscripts(allocAt)) {
 537         Descriptor allocElement{*Descriptor::Create(*allocDerived,
 538             reinterpret_cast<void *>(alloc.Element<char>(allocAt)), 0)};
 539         Assign(allocElement, source, terminator, NoAssignFlags);
 540       }
 541     } else { // intrinsic type
 542       for (std::size_t n{alloc.Elements()}; n-- > 0;
 543            alloc.IncrementSubscripts(allocAt)) {
 544         Fortran::runtime::memmove(alloc.Element<char>(allocAt),
 545             source.raw().base_addr, alloc.ElementBytes());
 546       }
 547     }
 548   } else {
 549     Assign(alloc, source, terminator, NoAssignFlags);
 550   }
 551 }
 552
 553 RT_OFFLOAD_API_GROUP_END
 554
 555 extern "C" {
 556 RT_EXT_API_GROUP_BEGIN
 557
 558 void RTDEF(Assign)(Descriptor &to, const Descriptor &from,
 559     const char *sourceFile, int sourceLine) {
 560   Terminator terminator{sourceFile, sourceLine};
 561   // All top-level defined assignments can be recognized in semantics and
 562   // will have been already been converted to calls, so don't check for
 563   // defined assignment apart from components.
 564   Assign(to, from, terminator,
 565       MaybeReallocate | NeedFinalization | ComponentCanBeDefinedAssignment);
 566 }
 567
 568 void RTDEF(AssignTemporary)(Descriptor &to, const Descriptor &from,
 569     const char *sourceFile, int sourceLine) {
 570   Terminator terminator{sourceFile, sourceLine};
 571   // Initialize the "to" if it is of derived type that needs initialization.
 572   if (const DescriptorAddendum * addendum{to.Addendum()}) {
 573     if (const auto *derived{addendum->derivedType()}) {
 574       // Do not invoke the initialization, if the descriptor is unallocated.
 575       // AssignTemporary() is used for component-by-component assignments,
 576       // for example, for structure constructors. This means that the LHS
 577       // may be an allocatable component with unallocated status.
 578       // The initialization will just fail in this case. By skipping
 579       // the initialization we let Assign() automatically allocate
 580       // and initialize the component according to the RHS.
 581       // So we only need to initialize the LHS here if it is allocated.
 582       // Note that initializing already initialized entity has no visible
 583       // effect, though, it is assumed that the compiler does not initialize
 584       // the temporary and leaves the initialization to this runtime code.
 585       if (!derived->noInitializationNeeded() && to.IsAllocated()) {
 586         if (ReturnError(terminator, Initialize(to, *derived, terminator)) !=
 587             StatOk) {
 588           return;
 589         }
 590       }
 591     }
 592   }
 593
 594   Assign(to, from, terminator, PolymorphicLHS);
 595 }
 596
 597 void RTDEF(CopyInAssign)(Descriptor &temp, const Descriptor &var,
 598     const char *sourceFile, int sourceLine) {
 599   Terminator terminator{sourceFile, sourceLine};
 600   temp = var;
 601   temp.set_base_addr(nullptr);
 602   temp.raw().attribute = CFI_attribute_allocatable;
 603   RTNAME(AssignTemporary)(temp, var, sourceFile, sourceLine);
 604 }
 605
 606 void RTDEF(CopyOutAssign)(
 607     Descriptor *var, Descriptor &temp, const char *sourceFile, int sourceLine) {
 608   Terminator terminator{sourceFile, sourceLine};
 609
 610   // Copyout from the temporary must not cause any finalizations
 611   // for LHS. The variable must be properly initialized already.
 612   if (var)
 613     Assign(*var, temp, terminator, NoAssignFlags);
 614   temp.Destroy(/*finalize=*/false, /*destroyPointers=*/false, &terminator);
 615 }
 616
 617 void RTDEF(AssignExplicitLengthCharacter)(Descriptor &to,
 618     const Descriptor &from, const char *sourceFile, int sourceLine) {
 619   Terminator terminator{sourceFile, sourceLine};
 620   Assign(to, from, terminator,
 621       MaybeReallocate | NeedFinalization | ComponentCanBeDefinedAssignment |
 622           ExplicitLengthCharacterLHS);
 623 }
 624
 625 void RTDEF(AssignPolymorphic)(Descriptor &to, const Descriptor &from,
 626     const char *sourceFile, int sourceLine) {
 627   Terminator terminator{sourceFile, sourceLine};
 628   Assign(to, from, terminator,
 629       MaybeReallocate | NeedFinalization | ComponentCanBeDefinedAssignment |
 630           PolymorphicLHS);
 631 }
 632
 633 RT_EXT_API_GROUP_END
 634 } // extern "C"
 635 } // namespace Fortran::runtime