[flang] CUDA Fortran - part 1/5: parsing

Begin upstreaming of CUDA Fortran support in LLVM Flang.

This first patch implements parsing for CUDA Fortran syntax,
including:
 - a new LanguageFeature enum value for CUDA Fortran
 - driver change to enable that feature for *.cuf and *.CUF source files
 - parse tree representation of CUDA Fortran syntax
 - dumping and unparsing of the parse tree
 - the actual parsers for CUDA Fortran syntax
 - prescanning support for !@CUF and !$CUF
 - basic sanity testing via unparsing and parse tree dumps

... along with any minimized changes elsewhere to make these
work, mostly no-op cases in common::visitors instances in
semantics and lowering to allow them to compile in the face
of new types in variant<> instances in the parse tree.

Because CUDA Fortran allows the kernel launch chevron syntax
("call foo<<<blocks, threads>>>()") only on CALL statements and
not on function references, the parse tree nodes for CallStmt,
FunctionReference, and their shared Call were rearranged a bit;
this caused a fair amount of one-line changes in many files.

More patches will follow that implement CUDA Fortran in the symbol
table and name resolution, and then semantic checking.

Differential Revision: https://reviews.llvm.org/D150159

1 files changed, 5 insertions, 4 deletions

diff --git a/flang/lib/Parser/preprocessor.cpp b/flang/lib/Parser/preprocessor.cpp
index 6dea129..1efe21a 100644
--- a/flang/lib/Parser/preprocessor.cpp
+++ b/flang/lib/Parser/preprocessor.cpp
@@ -622,11 +622,12 @@ void Preprocessor::Directive(const TokenSequence &dir, Prescanner &prescanner) {
       TokenSequence braced{dir, j + 1, k - j - 1};
       include = braced.ToString();
       j = k;
-    } else if ((include = dir.TokenAt(j).ToString()).substr(0, 1) == "\"" &&
-        include.substr(include.size() - 1, 1) == "\"") { // #include "foo"
+    } else if (((include = dir.TokenAt(j).ToString()).substr(0, 1) == "\"" ||
+                   include.substr(0, 1) == "'") &&
+        include.substr(include.size() - 1, 1) == include.substr(0, 1)) {
+      // #include "foo" and #include 'foo'
       include = include.substr(1, include.size() - 2);
-      // #include "foo" starts search in directory of file containing
-      // the directive
+      // Start search in directory of file containing the directive
       auto prov{dir.GetTokenProvenanceRange(dirOffset).start()};
       if (const auto *currentFile{allSources_.GetSourceFile(prov)}) {
         prependPath = DirectoryName(currentFile->path());