[flang] Use module file hashes for more checking and disambiguation

flang/include/flang/Parser/provenance.h

@@ -151,6 +151,7 @@ class AllSources {
 
   void ClearSearchPath();
   void AppendSearchPathDirectory(std::string); // new last directory
+  const SourceFile *OpenPath(std::string path, llvm::raw_ostream &error);
   const SourceFile *Open(std::string path, llvm::raw_ostream &error,
       std::optional<std::string> &&prependPath = std::nullopt);
   const SourceFile *ReadStandardInput(llvm::raw_ostream &error);

flang/include/flang/Parser/source.h

@@ -36,6 +36,8 @@ namespace Fortran::parser {
 std::string DirectoryName(std::string path);
 std::optional<std::string> LocateSourceFile(
     std::string name, const std::list<std::string> &searchPath);
+std::vector<std::string> LocateSourceFileAll(
+    std::string name, const std::vector<std::string> &searchPath);
 
 class SourceFile;
 

flang/include/flang/Semantics/module-dependences.h

@@ -0,0 +1,51 @@
+//===-- include/flang/Semantics/module-dependences.h ------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_SEMANTICS_MODULE_DEPENDENCES_H_
+#define FORTRAN_SEMANTICS_MODULE_DEPENDENCES_H_
+
+#include <cinttypes>
+#include <map>
+#include <optional>
+#include <string>
+
+namespace Fortran::semantics {
+
+using ModuleCheckSumType = std::uint64_t;
+
+class ModuleDependences {
+public:
+  void AddDependence(
+      std::string &&name, bool intrinsic, ModuleCheckSumType hash) {
+    if (intrinsic) {
+      intrinsicMap_.emplace(std::move(name), hash);
+    } else {
+      nonIntrinsicMap_.emplace(std::move(name), hash);
+    }
+  }
+  std::optional<ModuleCheckSumType> GetRequiredHash(
+      const std::string &name, bool intrinsic) {
+    if (intrinsic) {
+      if (auto iter{intrinsicMap_.find(name)}; iter != intrinsicMap_.end()) {
+        return iter->second;
+      }
+    } else {
+      if (auto iter{nonIntrinsicMap_.find(name)};
+          iter != nonIntrinsicMap_.end()) {
+        return iter->second;
+      }
+    }
+    return std::nullopt;
+  }
+
+private:
+  std::map<std::string, ModuleCheckSumType> intrinsicMap_, nonIntrinsicMap_;
+};
+
+} // namespace Fortran::semantics
+#endif // FORTRAN_SEMANTICS_MODULE_DEPENDENCES_H_

flang/include/flang/Semantics/semantics.h

@@ -16,6 +16,7 @@
 #include "flang/Evaluate/intrinsics.h"
 #include "flang/Evaluate/target.h"
 #include "flang/Parser/message.h"
+#include "flang/Semantics/module-dependences.h"
 #include <iosfwd>
 #include <set>
 #include <string>
@@ -108,6 +109,7 @@ class SemanticsContext {
   parser::Messages &messages() { return messages_; }
   evaluate::FoldingContext &foldingContext() { return foldingContext_; }
   parser::AllCookedSources &allCookedSources() { return allCookedSources_; }
+  ModuleDependences &moduleDependences() { return moduleDependences_; }
 
   SemanticsContext &set_location(
       const std::optional<parser::CharBlock> &location) {
@@ -293,6 +295,7 @@ class SemanticsContext {
   const Scope *ppcBuiltinsScope_{nullptr}; // module __ppc_intrinsics
   std::list<parser::Program> modFileParseTrees_;
   std::unique_ptr<CommonBlockMap> commonBlockMap_;
+  ModuleDependences moduleDependences_;
 };
 
 class Semantics {

flang/include/flang/Semantics/symbol.h

@@ -14,6 +14,7 @@
 #include "flang/Common/enum-set.h"
 #include "flang/Common/reference.h"
 #include "flang/Common/visit.h"
+#include "flang/Semantics/module-dependences.h"
 #include "llvm/ADT/DenseMapInfo.h"
 
 #include <array>
@@ -86,11 +87,16 @@ class ModuleDetails : public WithOmpDeclarative {
   void set_scope(const Scope *);
   bool isDefaultPrivate() const { return isDefaultPrivate_; }
   void set_isDefaultPrivate(bool yes = true) { isDefaultPrivate_ = yes; }
+  std::optional<ModuleCheckSumType> moduleFileHash() const {
+    return moduleFileHash_;
+  }
+  void set_moduleFileHash(ModuleCheckSumType x) { moduleFileHash_ = x; }
 
 private:
   bool isSubmodule_;
   bool isDefaultPrivate_{false};
   const Scope *scope_{nullptr};
+  std::optional<ModuleCheckSumType> moduleFileHash_;
 };
 
 class MainProgramDetails : public WithOmpDeclarative {
@@ -1035,7 +1041,7 @@ struct SymbolAddressCompare {
 // Symbol comparison is usually based on the order of cooked source
 // stream creation and, when both are from the same cooked source,
 // their positions in that cooked source stream.
-// Don't use this comparator or OrderedSymbolSet to hold
+// Don't use this comparator or SourceOrderedSymbolSet to hold
 // Symbols that might be subject to ReplaceName().
 struct SymbolSourcePositionCompare {
   // These functions are implemented in Evaluate/tools.cpp to

flang/lib/Parser/provenance.cpp

@@ -167,6 +167,16 @@ void AllSources::AppendSearchPathDirectory(std::string directory) {
   searchPath_.push_back(directory);
 }
 
+const SourceFile *AllSources::OpenPath(
+    std::string path, llvm::raw_ostream &error) {
+  std::unique_ptr<SourceFile> source{std::make_unique<SourceFile>(encoding_)};
+  if (source->Open(path, error)) {
+    return ownedSourceFiles_.emplace_back(std::move(source)).get();
+  } else {
+    return nullptr;
+  }
+}
+
 const SourceFile *AllSources::Open(std::string path, llvm::raw_ostream &error,
     std::optional<std::string> &&prependPath) {
   std::unique_ptr<SourceFile> source{std::make_unique<SourceFile>(encoding_)};
@@ -180,12 +190,10 @@ const SourceFile *AllSources::Open(std::string path, llvm::raw_ostream &error,
   if (prependPath) {
     searchPath_.pop_front();
   }
-  if (!found) {
-    error << "Source file '" << path << "' was not found";
-    return nullptr;
-  } else if (source->Open(*found, error)) {
-    return ownedSourceFiles_.emplace_back(std::move(source)).get();
+  if (found) {
+    return OpenPath(*found, error);
   } else {
+    error << "Source file '" << path << "' was not found";
     return nullptr;
   }
 }

flang/lib/Parser/source.cpp

@@ -75,6 +75,24 @@ std::optional<std::string> LocateSourceFile(
   return std::nullopt;
 }
 
+std::vector<std::string> LocateSourceFileAll(
+    std::string name, const std::vector<std::string> &searchPath) {
+  if (name == "-" || llvm::sys::path::is_absolute(name)) {
+    return {name};
+  }
+  std::vector<std::string> result;
+  for (const std::string &dir : searchPath) {
+    llvm::SmallString<128> path{dir};
+    llvm::sys::path::append(path, name);
+    bool isDir{false};
+    auto er = llvm::sys::fs::is_directory(path, isDir);
+    if (!er && !isDir) {
+      result.emplace_back(path.str().str());
+    }
+  }
+  return result;
+}
+
 std::size_t RemoveCarriageReturns(llvm::MutableArrayRef<char> buf) {
   std::size_t wrote{0};
   char *buffer{buf.data()};