[flang][driver] Fix support for `-x`

Until now, `-x` wasn't really taken into account in Flang's compiler and
frontend drivers. `flang-new` and `flang-new -fc1` only recently gained
powers to consume inputs other than Fortran files and that's probably
why this hasn't been noticed yet.

This patch makes sure that `-x` is supported correctly and consistently
with Clang. To this end, verification is added when reading LLVM IR
files (i.e. IR modules are verified with `llvm::verifyModule`). This
way, LLVM IR parsing errors are correctly reported to Flang users. This
also aids testing.

With the new functionality, we can verify that `-x ir` breaks
compilation for e.g. Fortran files and vice-versa. Tests are updated
accordingly.

Differential Revision: https://reviews.llvm.org/D127207

2 files changed, 21 insertions, 6 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 9ea4810..cc376f3 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -263,7 +263,10 @@ static bool parseFrontendArgs(FrontendOptions &opts, llvm::opt::ArgList &args,
     llvm::StringRef xValue = a->getValue();
     // Principal languages.
     dashX = llvm::StringSwitch<InputKind>(xValue)
-                .Case("f90", Language::Fortran)
+                // Flang does not differentiate between pre-processed and not
+                // pre-processed inputs.
+                .Case("f95", Language::Fortran)
+                .Case("f95-cpp-input", Language::Fortran)
                 .Default(Language::Unknown);
 
     // Some special cases cannot be combined with suffixes.
diff --git a/flang/lib/Frontend/FrontendActions.cpp b/flang/lib/Frontend/FrontendActions.cpp
index 334849c..57b6203 100644
--- a/flang/lib/Frontend/FrontendActions.cpp
+++ b/flang/lib/Frontend/FrontendActions.cpp
@@ -41,6 +41,7 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Bitcode/BitcodeWriterPass.h"
 #include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Verifier.h"
 #include "llvm/IRReader/IRReader.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Passes/PassBuilder.h"
@@ -78,25 +79,36 @@ bool PrescanAndSemaDebugAction::beginSourceFileAction() {
 
 bool CodeGenAction::beginSourceFileAction() {
   llvmCtx = std::make_unique<llvm::LLVMContext>();
+  CompilerInstance &ci = this->getInstance();
 
   // If the input is an LLVM file, just parse it and return.
   if (this->getCurrentInput().getKind().getLanguage() == Language::LLVM_IR) {
     llvm::SMDiagnostic err;
     llvmModule = llvm::parseIRFile(getCurrentInput().getFile(), err, *llvmCtx);
+    if (!llvmModule || llvm::verifyModule(*llvmModule, &llvm::errs())) {
+      err.print("flang-new", llvm::errs());
+      unsigned diagID = ci.getDiagnostics().getCustomDiagID(
+          clang::DiagnosticsEngine::Error, "Could not parse IR");
+      ci.getDiagnostics().Report(diagID);
+      return false;
+    }
 
-    return (nullptr != llvmModule);
+    return true;
   }
 
   // Otherwise, generate an MLIR module from the input Fortran source
-  assert(getCurrentInput().getKind().getLanguage() == Language::Fortran &&
-         "Invalid input type - expecting a Fortran file");
+  if (getCurrentInput().getKind().getLanguage() != Language::Fortran) {
+    unsigned diagID = ci.getDiagnostics().getCustomDiagID(
+        clang::DiagnosticsEngine::Error,
+        "Invalid input type - expecting a Fortran file");
+    ci.getDiagnostics().Report(diagID);
+    return false;
+  }
   bool res = runPrescan() && runParse() && runSemanticChecks() &&
              generateRtTypeTables();
   if (!res)
     return res;
 
-  CompilerInstance &ci = this->getInstance();
-
   // Load the MLIR dialects required by Flang
   mlir::DialectRegistry registry;
   mlirCtx = std::make_unique<mlir::MLIRContext>(registry);