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//===-- 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 "../../runtime/descriptor.h"
#include "flang/Evaluate/fold-designator.h"
#include "flang/Evaluate/fold.h"
#include "flang/Evaluate/shape.h"
#include "flang/Evaluate/type.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:
// TODO: configure based on target
static constexpr std::size_t maxAlignment{8};
ComputeOffsetsHelper(SemanticsContext &context) : context_{context} {}
void Compute() { Compute(context_.globalScope()); }
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;
Symbol *symbol;
std::size_t offset;
const EquivalenceObject *object;
};
void Compute(Scope &);
void DoScope(Scope &);
void DoCommonBlock(Symbol &);
void DoEquivalenceSet(const EquivalenceSet &);
SymbolAndOffset Resolve(const SymbolAndOffset &);
std::size_t ComputeOffset(const EquivalenceObject &);
void DoSymbol(Symbol &);
SizeAndAlignment GetSizeAndAlignment(const Symbol &);
SizeAndAlignment GetElementSize(const Symbol &);
std::size_t CountElements(const Symbol &);
static std::size_t Align(std::size_t, std::size_t);
static SizeAndAlignment GetIntrinsicSizeAndAlignment(TypeCategory, int);
SemanticsContext &context_;
evaluate::FoldingContext &foldingContext_{context_.foldingContext()};
std::size_t offset_{0};
std::size_t alignment_{0};
// symbol -> symbol+offset that determines its location, from EQUIVALENCE
std::map<MutableSymbolRef, SymbolAndOffset> dependents_;
};
void ComputeOffsetsHelper::Compute(Scope &scope) {
for (Scope &child : scope.children()) {
Compute(child);
}
DoScope(scope);
}
static bool InCommonBlock(const Symbol &symbol) {
const auto *details{symbol.detailsIf<ObjectEntityDetails>()};
return details && details->commonBlock();
}
void ComputeOffsetsHelper::DoScope(Scope &scope) {
if (scope.symbol() && scope.IsParameterizedDerivedType()) {
return; // only process instantiations of parameterized derived types
}
// Symbols in common block get offsets from the beginning of the block
for (auto &pair : scope.commonBlocks()) {
DoCommonBlock(*pair.second);
}
// Build dependents_ from equivalences: symbol -> symbol+offset
for (const EquivalenceSet &set : scope.equivalenceSets()) {
DoEquivalenceSet(set);
}
offset_ = 0;
alignment_ = 0;
for (auto &symbol : scope.GetSymbols()) {
if (!InCommonBlock(*symbol) &&
dependents_.find(symbol) == dependents_.end()) {
DoSymbol(*symbol);
}
}
for (auto &[symbol, dep] : dependents_) {
if (symbol->size() == 0) {
SizeAndAlignment s{GetSizeAndAlignment(*symbol)};
symbol->set_size(s.size);
SymbolAndOffset resolved{Resolve(dep)};
symbol->set_offset(dep.symbol->offset() + resolved.offset);
offset_ = std::max(offset_, symbol->offset() + symbol->size());
}
}
scope.set_size(offset_);
scope.set_alignment(alignment_);
}
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;
for (auto &object : details.objects()) {
DoSymbol(*object);
}
commonBlock.set_size(offset_);
details.set_alignment(alignment_);
}
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()) {
const ArraySpec &shape{object.symbol.get<ObjectEntityDetails>().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 * GetElementSize(object.symbol).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;
}
void ComputeOffsetsHelper::DoSymbol(Symbol &symbol) {
if (symbol.has<TypeParamDetails>() || symbol.has<SubprogramDetails>() ||
symbol.has<UseDetails>() || symbol.has<ProcBindingDetails>()) {
return; // these have type but no size
}
SizeAndAlignment s{GetSizeAndAlignment(symbol)};
if (s.size == 0) {
return;
}
offset_ = Align(offset_, s.alignment);
symbol.set_size(s.size);
symbol.set_offset(offset_);
offset_ += s.size;
alignment_ = std::max(alignment_, s.alignment);
}
auto ComputeOffsetsHelper::GetSizeAndAlignment(const Symbol &symbol)
-> SizeAndAlignment {
SizeAndAlignment result{GetElementSize(symbol)};
std::size_t elements{CountElements(symbol)};
if (elements > 1) {
result.size = Align(result.size, result.alignment);
}
result.size *= elements;
return result;
}
auto ComputeOffsetsHelper::GetElementSize(const Symbol &symbol)
-> SizeAndAlignment {
const DeclTypeSpec *type{symbol.GetType()};
if (!type) {
return {};
}
// TODO: The size of procedure pointers is not yet known
// and is independent of rank (and probably also the number
// of length type parameters).
if (IsDescriptor(symbol) || IsProcedure(symbol)) {
int lenParams{0};
if (const DerivedTypeSpec * derived{type->AsDerived()}) {
lenParams = CountLenParameters(*derived);
}
std::size_t size{
runtime::Descriptor::SizeInBytes(symbol.Rank(), false, lenParams)};
return {size, maxAlignment};
}
SizeAndAlignment result;
if (const IntrinsicTypeSpec * intrinsic{type->AsIntrinsic()}) {
if (auto kind{ToInt64(intrinsic->kind())}) {
result = GetIntrinsicSizeAndAlignment(intrinsic->category(), *kind);
}
if (type->category() == DeclTypeSpec::Character) {
ParamValue length{type->characterTypeSpec().length()};
CHECK(length.isExplicit()); // else should be descriptor
if (MaybeIntExpr lengthExpr{length.GetExplicit()}) {
if (auto lengthInt{ToInt64(*lengthExpr)}) {
result.size *= *lengthInt;
}
}
}
} else if (const DerivedTypeSpec * derived{type->AsDerived()}) {
if (derived->scope()) {
result.size = derived->scope()->size();
result.alignment = derived->scope()->alignment();
}
} else {
DIE("not intrinsic or derived");
}
return result;
}
std::size_t ComputeOffsetsHelper::CountElements(const Symbol &symbol) {
if (auto shape{GetShape(foldingContext_, symbol)}) {
if (auto sizeExpr{evaluate::GetSize(std::move(*shape))}) {
if (auto size{ToInt64(Fold(foldingContext_, std::move(*sizeExpr)))}) {
return *size;
}
}
}
return 1;
}
// Align a size to its natural alignment, up to maxAlignment.
std::size_t ComputeOffsetsHelper::Align(std::size_t x, std::size_t alignment) {
if (alignment > maxAlignment) {
alignment = maxAlignment;
}
return (x + alignment - 1) & -alignment;
}
auto ComputeOffsetsHelper::GetIntrinsicSizeAndAlignment(
TypeCategory category, int kind) -> SizeAndAlignment {
if (category == TypeCategory::Character) {
return {static_cast<std::size_t>(kind)};
}
std::optional<std::size_t> size{
evaluate::DynamicType{category, kind}.MeasureSizeInBytes()};
CHECK(size.has_value());
if (category == TypeCategory::Complex) {
return {*size, *size >> 1};
} else {
return {*size};
}
}
void ComputeOffsets(SemanticsContext &context) {
ComputeOffsetsHelper{context}.Compute();
}
} // namespace Fortran::semantics
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