Fail when clang FE returned an error

- Add check if clang diagnostics engine reported any errors
- Add basic tests for handling invalid C++ code by cgeist

Author: aobolensk

tools/cgeist/Lib/clang-mlir.cc

@@ -6136,6 +6136,10 @@ static bool parseMLIR(const char *Argv0, std::vector<std::string> filenames,
         Act.EndSourceFile();
       }
     }
+
+    if (Clang->getDiagnostics().hasErrorOccurred()) {
+      return false;
+    }
   }
   return true;
 }

tools/cgeist/Test/Verification/invalid/basic.cpp

@@ -0,0 +1,3 @@
+// RUN: not cgeist %s --function=* -S
+
+int main() {

tools/cgeist/Test/Verification/invalid/invalid_include.cpp

@@ -0,0 +1,3 @@
+// RUN: not cgeist %s --function=* -S
+
+#include "non-existing-header.h"

tools/cgeist/Test/Verification/ompParallelNumThreads.c

@@ -1,5 +1,6 @@
 // RUN: cgeist %s --function=* -fopenmp -S | FileCheck %s
-#include <omp.h>
+
+int omp_get_thread_num();
 
 void test_parallel_num_threads(double* x, int sinc) {
     // CHECK: %[[c32:.+]] = arith.constant 32 : i32

tools/cgeist/driver.cc

@@ -571,8 +571,11 @@ int main(int argc, char **argv) {
   llvm::DataLayout DL("");
   llvm::Triple gpuTriple;
   llvm::DataLayout gpuDL("");
-  parseMLIR(argv[0], files, cfunction, includeDirs, defines, module, triple, DL,
-            gpuTriple, gpuDL);
+  if (!parseMLIR(argv[0], files, cfunction, includeDirs, defines, module,
+                 triple, DL, gpuTriple, gpuDL)) {
+    llvm::errs() << "parseMLIR failed\n";
+    return 1;
+  }
 
   auto convertGepInBounds = [](llvm::Module &llvmModule) {
     for (auto &F : llvmModule) {