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//===-- lib/Semantics/rewrite-directives.cpp ------------------------------===//
//
// 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 "rewrite-directives.h"
#include "flang/Parser/parse-tree-visitor.h"
#include "flang/Parser/parse-tree.h"
#include "flang/Semantics/semantics.h"
#include "flang/Semantics/symbol.h"
#include "llvm/Frontend/OpenMP/OMP.h"
#include <list>
namespace Fortran::semantics {
using namespace parser::literals;
class DirectiveRewriteMutator {
public:
explicit DirectiveRewriteMutator(SemanticsContext &context)
: context_{context} {}
// Default action for a parse tree node is to visit children.
template <typename T> bool Pre(T &) { return true; }
template <typename T> void Post(T &) {}
protected:
SemanticsContext &context_;
};
// Rewrite atomic constructs to add an explicit memory ordering to all that do
// not specify it, honoring in this way the `atomic_default_mem_order` clause of
// the REQUIRES directive.
class OmpRewriteMutator : public DirectiveRewriteMutator {
public:
explicit OmpRewriteMutator(SemanticsContext &context)
: DirectiveRewriteMutator(context) {}
template <typename T> bool Pre(T &) { return true; }
template <typename T> void Post(T &) {}
bool Pre(parser::OpenMPAtomicConstruct &);
bool Pre(parser::OpenMPRequiresConstruct &);
private:
bool atomicDirectiveDefaultOrderFound_{false};
};
bool OmpRewriteMutator::Pre(parser::OpenMPAtomicConstruct &x) {
// Find top-level parent of the operation.
Symbol *topLevelParent{common::visit(
[&](auto &atomic) {
Symbol *symbol{nullptr};
Scope *scope{
&context_.FindScope(std::get<parser::Verbatim>(atomic.t).source)};
do {
if (Symbol * parent{scope->symbol()}) {
symbol = parent;
}
scope = &scope->parent();
} while (!scope->IsGlobal());
assert(symbol &&
"Atomic construct must be within a scope associated with a symbol");
return symbol;
},
x.u)};
// Get the `atomic_default_mem_order` clause from the top-level parent.
std::optional<common::OmpAtomicDefaultMemOrderType> defaultMemOrder;
common::visit(
[&](auto &details) {
if constexpr (std::is_convertible_v<decltype(&details),
WithOmpDeclarative *>) {
if (details.has_ompAtomicDefaultMemOrder()) {
defaultMemOrder = *details.ompAtomicDefaultMemOrder();
}
}
},
topLevelParent->details());
if (!defaultMemOrder) {
return false;
}
auto findMemOrderClause =
[](const std::list<parser::OmpAtomicClause> &clauses) {
return std::find_if(
clauses.begin(), clauses.end(), [](const auto &clause) {
return std::get_if<parser::OmpMemoryOrderClause>(
&clause.u);
}) != clauses.end();
};
// Get the clause list to which the new memory order clause must be added,
// only if there are no other memory order clauses present for this atomic
// directive.
std::list<parser::OmpAtomicClause> *clauseList = common::visit(
common::visitors{[&](parser::OmpAtomic &atomicConstruct) {
// OmpAtomic only has a single list of clauses.
auto &clauses{std::get<parser::OmpAtomicClauseList>(
atomicConstruct.t)};
return !findMemOrderClause(clauses.v) ? &clauses.v
: nullptr;
},
[&](auto &atomicConstruct) {
// All other atomic constructs have two lists of clauses.
auto &clausesLhs{std::get<0>(atomicConstruct.t)};
auto &clausesRhs{std::get<2>(atomicConstruct.t)};
return !findMemOrderClause(clausesLhs.v) &&
!findMemOrderClause(clausesRhs.v)
? &clausesRhs.v
: nullptr;
}},
x.u);
// Add a memory order clause to the atomic directive.
if (clauseList) {
atomicDirectiveDefaultOrderFound_ = true;
switch (*defaultMemOrder) {
case common::OmpAtomicDefaultMemOrderType::AcqRel:
clauseList->emplace_back<parser::OmpMemoryOrderClause>(common::visit(
common::visitors{[](parser::OmpAtomicRead &) -> parser::OmpClause {
return parser::OmpClause::Acquire{};
},
[](parser::OmpAtomicCapture &) -> parser::OmpClause {
return parser::OmpClause::AcqRel{};
},
[](auto &) -> parser::OmpClause {
// parser::{OmpAtomic, OmpAtomicUpdate, OmpAtomicWrite}
return parser::OmpClause::Release{};
}},
x.u));
break;
case common::OmpAtomicDefaultMemOrderType::Relaxed:
clauseList->emplace_back<parser::OmpMemoryOrderClause>(
parser::OmpClause{parser::OmpClause::Relaxed{}});
break;
case common::OmpAtomicDefaultMemOrderType::SeqCst:
clauseList->emplace_back<parser::OmpMemoryOrderClause>(
parser::OmpClause{parser::OmpClause::SeqCst{}});
break;
}
}
return false;
}
bool OmpRewriteMutator::Pre(parser::OpenMPRequiresConstruct &x) {
for (parser::OmpClause &clause : std::get<parser::OmpClauseList>(x.t).v) {
if (std::holds_alternative<parser::OmpClause::AtomicDefaultMemOrder>(
clause.u) &&
atomicDirectiveDefaultOrderFound_) {
context_.Say(clause.source,
"REQUIRES directive with '%s' clause found lexically after atomic "
"operation without a memory order clause"_err_en_US,
parser::ToUpperCaseLetters(llvm::omp::getOpenMPClauseName(
llvm::omp::OMPC_atomic_default_mem_order)
.str()));
}
}
return false;
}
bool RewriteOmpParts(SemanticsContext &context, parser::Program &program) {
if (!context.IsEnabled(common::LanguageFeature::OpenMP)) {
return true;
}
OmpRewriteMutator ompMutator{context};
parser::Walk(program, ompMutator);
return !context.AnyFatalError();
}
} // namespace Fortran::semantics
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