[flang] Distinguish intrinsic from non-intrinsic modules

For "USE, INTRINSIC", search only for intrinsic modules;
for "USE, NON_INTRINSIC", do not recognize intrinsic modules.
Allow modules of both kinds with the same name to be used in
the same source file (but not in the same scoping unit, a
constraint of the standard that is now enforced).

The symbol table's scope tree now has a single instance of
a scope with a new kind, IntrinsicModules, whose children are
the USE'd intrinsic modules (explicit or not).  This separate
"top-level" scope is a child of the single global scope and
it allows both intrinsic and non-intrinsic modules of the same
name to exist in the symbol table.  Intrinsic modules' scopes'
symbols now have the INTRINSIC attribute set.

The search path directories need to make a distinction between
regular directories and the one(s) that point(s) to intrinsic
modules.  I allow for multiple intrinsic module directories in
the second search path, although only one is needed today.

Differential Revision: https://reviews.llvm.org/D118631

1 files changed, 3 insertions, 2 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 2d8c9e3..dcfa741 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -658,8 +658,8 @@ void CompilerInvocation::SetFortranOpts() {
       preprocessorOptions.searchDirectoriesFromIntrModPath.begin(),
       preprocessorOptions.searchDirectoriesFromIntrModPath.end());
 
-  //  Add the default intrinsic module directory at the end
-  fortranOptions.searchDirectories.emplace_back(getIntrinsicDir());
+  //  Add the default intrinsic module directory
+  fortranOptions.intrinsicModuleDirectories.emplace_back(getIntrinsicDir());
 
   // Add the directory supplied through -J/-module-dir to the list of search
   // directories
@@ -686,6 +686,7 @@ void CompilerInvocation::SetSemanticsOpts(
 
   semanticsContext_->set_moduleDirectory(moduleDir())
       .set_searchDirectories(fortranOptions.searchDirectories)
+      .set_intrinsicModuleDirectories(fortranOptions.intrinsicModuleDirectories)
       .set_warnOnNonstandardUsage(enableConformanceChecks())
       .set_warningsAreErrors(warnAsErr())
       .set_moduleFileSuffix(moduleFileSuffix());