xref: /llvm-project/flang/lib/Semantics/rewrite-parse-tree.cpp (revision fbbd8b0741586794721639715d1d974db56f83ac) 
1 //===-- lib/Semantics/rewrite-parse-tree.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 "rewrite-parse-tree.h"
10 #include "rewrite-directives.h"
11 #include "flang/Common/indirection.h"
12 #include "flang/Parser/parse-tree-visitor.h"
13 #include "flang/Parser/parse-tree.h"
14 #include "flang/Parser/tools.h"
15 #include "flang/Semantics/scope.h"
16 #include "flang/Semantics/semantics.h"
17 #include "flang/Semantics/symbol.h"
18 #include "flang/Semantics/tools.h"
19 #include <list>
20 
21 namespace Fortran::semantics {
22 
23 using namespace parser::literals;
24 
25 /// Convert misidentified statement functions to array element assignments
26 /// or pointer-valued function result assignments.
27 /// Convert misidentified format expressions to namelist group names.
28 /// Convert misidentified character variables in I/O units to integer
29 /// unit number expressions.
30 /// Convert misidentified named constants in data statement values to
31 /// initial data targets
32 class RewriteMutator {
33 public:
34   RewriteMutator(SemanticsContext &context)
35       : context_{context}, errorOnUnresolvedName_{!context.AnyFatalError()},
36         messages_{context.messages()} {}
37 
38   // Default action for a parse tree node is to visit children.
39   template <typename T> bool Pre(T &) { return true; }
40   template <typename T> void Post(T &) {}
41 
42   void Post(parser::Name &);
43   bool Pre(parser::MainProgram &);
44   bool Pre(parser::FunctionSubprogram &);
45   bool Pre(parser::SubroutineSubprogram &);
46   bool Pre(parser::SeparateModuleSubprogram &);
47   bool Pre(parser::BlockConstruct &);
48   bool Pre(parser::ActionStmt &);
49   void Post(parser::ReadStmt &);
50   void Post(parser::WriteStmt &);
51 
52   // Name resolution yet implemented:
53   // TODO: Can some/all of these now be enabled?
54   bool Pre(parser::EquivalenceStmt &) { return false; }
55   bool Pre(parser::Keyword &) { return false; }
56   bool Pre(parser::EntryStmt &) { return false; }
57   bool Pre(parser::CompilerDirective &) { return false; }
58 
59   // Don't bother resolving names in end statements.
60   bool Pre(parser::EndBlockDataStmt &) { return false; }
61   bool Pre(parser::EndFunctionStmt &) { return false; }
62   bool Pre(parser::EndInterfaceStmt &) { return false; }
63   bool Pre(parser::EndModuleStmt &) { return false; }
64   bool Pre(parser::EndMpSubprogramStmt &) { return false; }
65   bool Pre(parser::EndProgramStmt &) { return false; }
66   bool Pre(parser::EndSubmoduleStmt &) { return false; }
67   bool Pre(parser::EndSubroutineStmt &) { return false; }
68   bool Pre(parser::EndTypeStmt &) { return false; }
69 
70 private:
71   void FixMisparsedStmtFuncs(parser::SpecificationPart &, parser::Block &);
72 
73   SemanticsContext &context_;
74   bool errorOnUnresolvedName_{true};
75   parser::Messages &messages_;
76 };
77 
78 // Check that name has been resolved to a symbol
79 void RewriteMutator::Post(parser::Name &name) {
80   if (!name.symbol && errorOnUnresolvedName_) {
81     messages_.Say(name.source, "Internal: no symbol found for '%s'"_err_en_US,
82         name.source);
83   }
84 }
85 
86 static bool ReturnsDataPointer(const Symbol &symbol) {
87   if (const Symbol * funcRes{FindFunctionResult(symbol)}) {
88     return IsPointer(*funcRes) && !IsProcedure(*funcRes);
89   } else if (const auto *generic{symbol.detailsIf<GenericDetails>()}) {
90     for (auto ref : generic->specificProcs()) {
91       if (ReturnsDataPointer(*ref)) {
92         return true;
93       }
94     }
95   }
96   return false;
97 }
98 
99 // Finds misparsed statement functions in a specification part, rewrites
100 // them into array element assignment statements, and moves them into the
101 // beginning of the corresponding (execution part's) block.
102 void RewriteMutator::FixMisparsedStmtFuncs(
103     parser::SpecificationPart &specPart, parser::Block &block) {
104   auto &list{std::get<std::list<parser::DeclarationConstruct>>(specPart.t)};
105   auto origFirst{block.begin()}; // insert each elem before origFirst
106   for (auto it{list.begin()}; it != list.end();) {
107     bool convert{false};
108     if (auto *stmt{std::get_if<
109             parser::Statement<common::Indirection<parser::StmtFunctionStmt>>>(
110             &it->u)}) {
111       if (const Symbol *
112           symbol{std::get<parser::Name>(stmt->statement.value().t).symbol}) {
113         const Symbol &ultimate{symbol->GetUltimate()};
114         convert =
115             ultimate.has<ObjectEntityDetails>() || ReturnsDataPointer(ultimate);
116         if (convert) {
117           auto newStmt{stmt->statement.value().ConvertToAssignment()};
118           newStmt.source = stmt->source;
119           block.insert(origFirst,
120               parser::ExecutionPartConstruct{
121                   parser::ExecutableConstruct{std::move(newStmt)}});
122         }
123       }
124     }
125     if (convert) {
126       it = list.erase(it);
127     } else {
128       ++it;
129     }
130   }
131 }
132 
133 bool RewriteMutator::Pre(parser::MainProgram &program) {
134   FixMisparsedStmtFuncs(std::get<parser::SpecificationPart>(program.t),
135       std::get<parser::ExecutionPart>(program.t).v);
136   return true;
137 }
138 
139 bool RewriteMutator::Pre(parser::FunctionSubprogram &func) {
140   FixMisparsedStmtFuncs(std::get<parser::SpecificationPart>(func.t),
141       std::get<parser::ExecutionPart>(func.t).v);
142   return true;
143 }
144 
145 bool RewriteMutator::Pre(parser::SubroutineSubprogram &subr) {
146   FixMisparsedStmtFuncs(std::get<parser::SpecificationPart>(subr.t),
147       std::get<parser::ExecutionPart>(subr.t).v);
148   return true;
149 }
150 
151 bool RewriteMutator::Pre(parser::SeparateModuleSubprogram &subp) {
152   FixMisparsedStmtFuncs(std::get<parser::SpecificationPart>(subp.t),
153       std::get<parser::ExecutionPart>(subp.t).v);
154   return true;
155 }
156 
157 bool RewriteMutator::Pre(parser::BlockConstruct &block) {
158   FixMisparsedStmtFuncs(std::get<parser::BlockSpecificationPart>(block.t).v,
159       std::get<parser::Block>(block.t));
160   return true;
161 }
162 
163 // Rewrite PRINT NML -> WRITE(*,NML=NML)
164 bool RewriteMutator::Pre(parser::ActionStmt &x) {
165   if (auto *print{std::get_if<common::Indirection<parser::PrintStmt>>(&x.u)};
166       print &&
167       std::get<std::list<parser::OutputItem>>(print->value().t).empty()) {
168     auto &format{std::get<parser::Format>(print->value().t)};
169     if (std::holds_alternative<parser::Expr>(format.u)) {
170       if (auto *name{parser::Unwrap<parser::Name>(format)}; name &&
171           name->symbol && name->symbol->GetUltimate().has<NamelistDetails>() &&
172           context_.IsEnabled(common::LanguageFeature::PrintNamelist)) {
173         context_.Warn(common::LanguageFeature::PrintNamelist, name->source,
174             "nonstandard: namelist in PRINT statement"_port_en_US);
175         std::list<parser::IoControlSpec> controls;
176         controls.emplace_back(std::move(*name));
177         x.u = common::Indirection<parser::WriteStmt>::Make(
178             parser::IoUnit{parser::Star{}}, std::optional<parser::Format>{},
179             std::move(controls), std::list<parser::OutputItem>{});
180       }
181     }
182   }
183   return true;
184 }
185 
186 // When a namelist group name appears (without NML=) in a READ or WRITE
187 // statement in such a way that it can be misparsed as a format expression,
188 // rewrite the I/O statement's parse tree node as if the namelist group
189 // name had appeared with NML=.
190 template <typename READ_OR_WRITE>
191 void FixMisparsedUntaggedNamelistName(READ_OR_WRITE &x) {
192   if (x.iounit && x.format &&
193       std::holds_alternative<parser::Expr>(x.format->u)) {
194     if (const parser::Name * name{parser::Unwrap<parser::Name>(x.format)}) {
195       if (name->symbol && name->symbol->GetUltimate().has<NamelistDetails>()) {
196         x.controls.emplace_front(parser::IoControlSpec{std::move(*name)});
197         x.format.reset();
198       }
199     }
200   }
201 }
202 
203 // READ(CVAR) [, ...] will be misparsed as UNIT=CVAR; correct
204 // it to READ CVAR [,...] with CVAR as a format rather than as
205 // an internal I/O unit for unformatted I/O, which Fortran does
206 // not support.
207 void RewriteMutator::Post(parser::ReadStmt &x) {
208   if (x.iounit && !x.format && x.controls.empty()) {
209     if (auto *var{std::get_if<parser::Variable>(&x.iounit->u)}) {
210       const parser::Name &last{parser::GetLastName(*var)};
211       DeclTypeSpec *type{last.symbol ? last.symbol->GetType() : nullptr};
212       if (type && type->category() == DeclTypeSpec::Character) {
213         x.format = common::visit(
214             [](auto &&indirection) {
215               return parser::Expr{std::move(indirection)};
216             },
217             std::move(var->u));
218         x.iounit.reset();
219       }
220     }
221   }
222   FixMisparsedUntaggedNamelistName(x);
223 }
224 
225 void RewriteMutator::Post(parser::WriteStmt &x) {
226   FixMisparsedUntaggedNamelistName(x);
227 }
228 
229 bool RewriteParseTree(SemanticsContext &context, parser::Program &program) {
230   RewriteMutator mutator{context};
231   parser::Walk(program, mutator);
232   return !context.AnyFatalError() && RewriteOmpParts(context, program);
233 }
234 
235 } // namespace Fortran::semantics
236