//===-- lib/Semantics/compute-offsets.cpp -----------------------*- C++ -*-===//
//
// 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 "compute-offsets.h"
#include "flang/Evaluate/fold-designator.h"
#include "flang/Evaluate/fold.h"
#include "flang/Evaluate/shape.h"
#include "flang/Evaluate/type.h"
#include "flang/Runtime/descriptor.h"
#include "flang/Semantics/scope.h"
#include "flang/Semantics/semantics.h"
#include "flang/Semantics/symbol.h"
#include "flang/Semantics/tools.h"
#include "flang/Semantics/type.h"
#include <algorithm>
#include <vector>
namespace Fortran::semantics {
class ComputeOffsetsHelper {
public:
ComputeOffsetsHelper(SemanticsContext &context) : context_{context} {}
void Compute(Scope &);
private:
struct SizeAndAlignment {
SizeAndAlignment() {}
SizeAndAlignment(std::size_t bytes) : size{bytes}, alignment{bytes} {}
SizeAndAlignment(std::size_t bytes, std::size_t align)
: size{bytes}, alignment{align} {}
std::size_t size{0};
std::size_t alignment{0};
};
struct SymbolAndOffset {
SymbolAndOffset(Symbol &s, std::size_t off, const EquivalenceObject &obj)
: symbol{s}, offset{off}, object{&obj} {}
SymbolAndOffset(const SymbolAndOffset &) = default;
MutableSymbolRef symbol;
std::size_t offset;
const EquivalenceObject *object;
};
void DoCommonBlock(Symbol &);
void DoEquivalenceBlockBase(Symbol &, SizeAndAlignment &);
void DoEquivalenceSet(const EquivalenceSet &);
SymbolAndOffset Resolve(const SymbolAndOffset &);
std::size_t ComputeOffset(const EquivalenceObject &);
// Returns amount of padding that was needed for alignment
std::size_t DoSymbol(Symbol &);
SizeAndAlignment GetSizeAndAlignment(const Symbol &, bool entire);
std::size_t Align(std::size_t, std::size_t);
SemanticsContext &context_;
std::size_t offset_{0};
std::size_t alignment_{1};
// symbol -> symbol+offset that determines its location, from EQUIVALENCE
std::map<MutableSymbolRef, SymbolAndOffset, SymbolAddressCompare> dependents_;
// base symbol -> SizeAndAlignment for each distinct EQUIVALENCE block
std::map<MutableSymbolRef, SizeAndAlignment, SymbolAddressCompare>
equivalenceBlock_;
};
void ComputeOffsetsHelper::Compute(Scope &scope) {
for (Scope &child : scope.children()) {
ComputeOffsets(context_, child);
}
if (scope.symbol() && scope.IsDerivedTypeWithKindParameter()) {
return; // only process instantiations of kind parameterized derived types
}
if (scope.alignment().has_value()) {
return; // prevent infinite recursion in error cases
}
scope.SetAlignment(0);
// Build dependents_ from equivalences: symbol -> symbol+offset
for (const EquivalenceSet &set : scope.equivalenceSets()) {
DoEquivalenceSet(set);
}
// Compute a base symbol and overall block size for each
// disjoint EQUIVALENCE storage sequence.
for (auto &[symbol, dep] : dependents_) {
dep = Resolve(dep);
CHECK(symbol->size() == 0);
auto symInfo{GetSizeAndAlignment(*symbol, true)};
symbol->set_size(symInfo.size);
Symbol &base{*dep.symbol};
auto iter{equivalenceBlock_.find(base)};
std::size_t minBlockSize{dep.offset + symInfo.size};
if (iter == equivalenceBlock_.end()) {
equivalenceBlock_.emplace(
base, SizeAndAlignment{minBlockSize, symInfo.alignment});
} else {
SizeAndAlignment &blockInfo{iter->second};
blockInfo.size = std::max(blockInfo.size, minBlockSize);
blockInfo.alignment = std::max(blockInfo.alignment, symInfo.alignment);
}
}
// Assign offsets for non-COMMON EQUIVALENCE blocks
for (auto &[symbol, blockInfo] : equivalenceBlock_) {
if (!FindCommonBlockContaining(*symbol)) {
DoSymbol(*symbol);
DoEquivalenceBlockBase(*symbol, blockInfo);
offset_ = std::max(offset_, symbol->offset() + blockInfo.size);
}
}
// Process remaining non-COMMON symbols; this is all of them if there
// was no use of EQUIVALENCE in the scope.
for (auto &symbol : scope.GetSymbols()) {
if (!FindCommonBlockContaining(*symbol) &&
dependents_.find(symbol) == dependents_.end() &&
equivalenceBlock_.find(symbol) == equivalenceBlock_.end()) {
DoSymbol(*symbol);
if (auto *generic{symbol->detailsIf<GenericDetails>()}) {
if (Symbol * specific{generic->specific()};
specific && !FindCommonBlockContaining(*specific)) {
// might be a shadowed procedure pointer
DoSymbol(*specific);
}
}
}
}
// Ensure that the size is a multiple of the alignment
offset_ = Align(offset_, alignment_);
scope.set_size(offset_);
scope.SetAlignment(alignment_);
// Assign offsets in COMMON blocks, unless this scope is a BLOCK construct,
// where COMMON blocks are illegal (C1107 and C1108).
if (scope.kind() != Scope::Kind::BlockConstruct) {
for (auto &pair : scope.commonBlocks()) {
DoCommonBlock(*pair.second);
}
}
for (auto &[symbol, dep] : dependents_) {
symbol->set_offset(dep.symbol->offset() + dep.offset);
if (const auto *block{FindCommonBlockContaining(*dep.symbol)}) {
symbol->get<ObjectEntityDetails>().set_commonBlock(*block);
}
}
}
auto ComputeOffsetsHelper::Resolve(const SymbolAndOffset &dep)
-> SymbolAndOffset {
auto it{dependents_.find(*dep.symbol)};
if (it == dependents_.end()) {
return dep;
} else {
SymbolAndOffset result{Resolve(it->second)};
result.offset += dep.offset;
result.object = dep.object;
return result;
}
}
void ComputeOffsetsHelper::DoCommonBlock(Symbol &commonBlock) {
auto &details{commonBlock.get<CommonBlockDetails>()};
offset_ = 0;
alignment_ = 0;
std::size_t minSize{0};
std::size_t minAlignment{0};
UnorderedSymbolSet previous;
for (auto object : details.objects()) {
Symbol &symbol{*object};
auto errorSite{
commonBlock.name().empty() ? symbol.name() : commonBlock.name()};
if (std::size_t padding{DoSymbol(symbol.GetUltimate())}) {
if (context_.ShouldWarn(common::UsageWarning::CommonBlockPadding)) {
context_.Say(errorSite,
"COMMON block /%s/ requires %zd bytes of padding before '%s' for alignment"_port_en_US,
commonBlock.name(), padding, symbol.name());
}
}
previous.emplace(symbol);
auto eqIter{equivalenceBlock_.end()};
auto iter{dependents_.find(symbol)};
if (iter == dependents_.end()) {
eqIter = equivalenceBlock_.find(symbol);
if (eqIter != equivalenceBlock_.end()) {
DoEquivalenceBlockBase(symbol, eqIter->second);
}
} else {
SymbolAndOffset &dep{iter->second};
Symbol &base{*dep.symbol};
if (const auto *baseBlock{FindCommonBlockContaining(base)}) {
if (baseBlock == &commonBlock) {
if (previous.find(SymbolRef{base}) == previous.end() ||
base.offset() != symbol.offset() - dep.offset) {
context_.Say(errorSite,
"'%s' is storage associated with '%s' by EQUIVALENCE elsewhere in COMMON block /%s/"_err_en_US,
symbol.name(), base.name(), commonBlock.name());
}
} else { // F'2023 8.10.3 p1
context_.Say(errorSite,
"'%s' in COMMON block /%s/ must not be storage associated with '%s' in COMMON block /%s/ by EQUIVALENCE"_err_en_US,
symbol.name(), commonBlock.name(), base.name(),
baseBlock->name());
}
} else if (dep.offset > symbol.offset()) { // 8.10.3(3)
context_.Say(errorSite,
"'%s' cannot backward-extend COMMON block /%s/ via EQUIVALENCE with '%s'"_err_en_US,
symbol.name(), commonBlock.name(), base.name());
} else {
eqIter = equivalenceBlock_.find(base);
base.get<ObjectEntityDetails>().set_commonBlock(commonBlock);
base.set_offset(symbol.offset() - dep.offset);
previous.emplace(base);
}
}
// Get full extent of any EQUIVALENCE block into size of COMMON ( see
// 8.10.2.2 point 1 (2))
if (eqIter != equivalenceBlock_.end()) {
SizeAndAlignment &blockInfo{eqIter->second};
minSize = std::max(
minSize, std::max(offset_, eqIter->first->offset() + blockInfo.size));
minAlignment = std::max(minAlignment, blockInfo.alignment);
}
}
commonBlock.set_size(std::max(minSize, offset_));
details.set_alignment(std::max(minAlignment, alignment_));
context_.MapCommonBlockAndCheckConflicts(commonBlock);
}
void ComputeOffsetsHelper::DoEquivalenceBlockBase(
Symbol &symbol, SizeAndAlignment &blockInfo) {
if (symbol.size() > blockInfo.size) {
blockInfo.size = symbol.size();
}
}
void ComputeOffsetsHelper::DoEquivalenceSet(const EquivalenceSet &set) {
std::vector<SymbolAndOffset> symbolOffsets;
std::optional<std::size_t> representative;
for (const EquivalenceObject &object : set) {
std::size_t offset{ComputeOffset(object)};
SymbolAndOffset resolved{
Resolve(SymbolAndOffset{object.symbol, offset, object})};
symbolOffsets.push_back(resolved);
if (!representative ||
resolved.offset >= symbolOffsets[*representative].offset) {
// The equivalenced object with the largest offset from its resolved
// symbol will be the representative of this set, since the offsets
// of the other objects will be positive relative to it.
representative = symbolOffsets.size() - 1;
}
}
CHECK(representative);
const SymbolAndOffset &base{symbolOffsets[*representative]};
for (const auto &[symbol, offset, object] : symbolOffsets) {
if (symbol == base.symbol) {
if (offset != base.offset) {
auto x{evaluate::OffsetToDesignator(
context_.foldingContext(), *symbol, base.offset, 1)};
auto y{evaluate::OffsetToDesignator(
context_.foldingContext(), *symbol, offset, 1)};
if (x && y) {
context_
.Say(base.object->source,
"'%s' and '%s' cannot have the same first storage unit"_err_en_US,
x->AsFortran(), y->AsFortran())
.Attach(object->source, "Incompatible reference to '%s'"_en_US,
y->AsFortran());
} else { // error recovery
context_
.Say(base.object->source,
"'%s' (offset %zd bytes and %zd bytes) cannot have the same first storage unit"_err_en_US,
symbol->name(), base.offset, offset)
.Attach(object->source,
"Incompatible reference to '%s' offset %zd bytes"_en_US,
symbol->name(), offset);
}
}
} else {
dependents_.emplace(*symbol,
SymbolAndOffset{*base.symbol, base.offset - offset, *object});
}
}
}
// Offset of this equivalence object from the start of its variable.
std::size_t ComputeOffsetsHelper::ComputeOffset(
const EquivalenceObject &object) {
std::size_t offset{0};
if (!object.subscripts.empty()) {
if (const auto *details{object.symbol.detailsIf<ObjectEntityDetails>()}) {
const ArraySpec &shape{details->shape()};
auto lbound{[&](std::size_t i) {
return *ToInt64(shape[i].lbound().GetExplicit());
}};
auto ubound{[&](std::size_t i) {
return *ToInt64(shape[i].ubound().GetExplicit());
}};
for (std::size_t i{object.subscripts.size() - 1};;) {
offset += object.subscripts[i] - lbound(i);
if (i == 0) {
break;
}
--i;
offset *= ubound(i) - lbound(i) + 1;
}
}
}
auto result{offset * GetSizeAndAlignment(object.symbol, false).size};
if (object.substringStart) {
int kind{context_.defaultKinds().GetDefaultKind(TypeCategory::Character)};
if (const DeclTypeSpec * type{object.symbol.GetType()}) {
if (const IntrinsicTypeSpec * intrinsic{type->AsIntrinsic()}) {
kind = ToInt64(intrinsic->kind()).value_or(kind);
}
}
result += kind * (*object.substringStart - 1);
}
return result;
}
std::size_t ComputeOffsetsHelper::DoSymbol(Symbol &symbol) {
if (!symbol.has<ObjectEntityDetails>() && !symbol.has<ProcEntityDetails>()) {
return 0;
}
SizeAndAlignment s{GetSizeAndAlignment(symbol, true)};
if (s.size == 0) {
return 0;
}
std::size_t previousOffset{offset_};
offset_ = Align(offset_, s.alignment);
std::size_t padding{offset_ - previousOffset};
symbol.set_size(s.size);
symbol.set_offset(offset_);
offset_ += s.size;
alignment_ = std::max(alignment_, s.alignment);
return padding;
}
auto ComputeOffsetsHelper::GetSizeAndAlignment(
const Symbol &symbol, bool entire) -> SizeAndAlignment {
auto &targetCharacteristics{context_.targetCharacteristics()};
if (IsDescriptor(symbol)) {
auto dyType{evaluate::DynamicType::From(symbol)};
const auto *derived{evaluate::GetDerivedTypeSpec(dyType)};
int lenParams{derived ? CountLenParameters(*derived) : 0};
bool needAddendum{derived || (dyType && dyType->IsUnlimitedPolymorphic())};
std::size_t size{runtime::Descriptor::SizeInBytes(
symbol.Rank(), needAddendum, lenParams)};
return {size, targetCharacteristics.descriptorAlignment()};
}
if (IsProcedurePointer(symbol)) {
return {targetCharacteristics.procedurePointerByteSize(),
targetCharacteristics.procedurePointerAlignment()};
}
if (IsProcedure(symbol)) {
return {};
}
auto &foldingContext{context_.foldingContext()};
if (auto chars{evaluate::characteristics::TypeAndShape::Characterize(
symbol, foldingContext)}) {
if (entire) {
if (auto size{ToInt64(chars->MeasureSizeInBytes(foldingContext))}) {
return {static_cast<std::size_t>(*size),
chars->type().GetAlignment(targetCharacteristics)};
}
} else { // element size only
if (auto size{ToInt64(chars->MeasureElementSizeInBytes(
foldingContext, true /*aligned*/))}) {
return {static_cast<std::size_t>(*size),
chars->type().GetAlignment(targetCharacteristics)};
}
}
}
return {};
}
// Align a size to its natural alignment, up to maxAlignment.
std::size_t ComputeOffsetsHelper::Align(std::size_t x, std::size_t alignment) {
alignment =
std::min(alignment, context_.targetCharacteristics().maxAlignment());
return (x + alignment - 1) & -alignment;
}
void ComputeOffsets(SemanticsContext &context, Scope &scope) {
ComputeOffsetsHelper{context}.Compute(scope);
}
} // namespace Fortran::semantics
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