diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -815,7 +815,7 @@
 
 void CompilerInvocation::setSemanticsOpts(
     Fortran::parser::AllCookedSources &allCookedSources) {
-  const auto &fortranOptions = getFortranOpts();
+  auto &fortranOptions = getFortranOpts();
 
   semanticsContext = std::make_unique<semantics::SemanticsContext>(
       getDefaultKinds(), fortranOptions.features, allCookedSources);
@@ -829,10 +829,14 @@
 
   llvm::Triple targetTriple{llvm::Triple(this->targetOpts.triple)};
   // FIXME: Handle real(3) ?
-  if (targetTriple.getArch() != llvm::Triple::ArchType::x86 &&
-      targetTriple.getArch() != llvm::Triple::ArchType::x86_64) {
+  if (targetTriple.getArch() != llvm::Triple::ArchType::x86_64) {
     semanticsContext->targetCharacteristics().DisableType(
         Fortran::common::TypeCategory::Real, /*kind=*/10);
+  } else {
+    const auto &preprocessorOptions = getPreprocessorOpts();
+    if (preprocessorOptions.macrosFlag == PPMacrosFlag::Include) {
+      fortranOptions.predefinitions.emplace_back("__x86_64__", "1");
+    }
   }
 }
 
diff --git a/flang/tools/f18/CMakeLists.txt b/flang/tools/f18/CMakeLists.txt
--- a/flang/tools/f18/CMakeLists.txt
+++ b/flang/tools/f18/CMakeLists.txt
@@ -39,7 +39,7 @@
     endif()
     add_custom_command(OUTPUT ${base}.mod
       COMMAND ${CMAKE_COMMAND} -E make_directory ${FLANG_INTRINSIC_MODULES_DIR}
-      COMMAND flang-new -fc1 -fsyntax-only -module-dir ${FLANG_INTRINSIC_MODULES_DIR}
+      COMMAND flang-new -fc1 -cpp -fsyntax-only -module-dir ${FLANG_INTRINSIC_MODULES_DIR}
         ${FLANG_SOURCE_DIR}/module/${filename}.f90
       DEPENDS flang-new ${FLANG_SOURCE_DIR}/module/${filename}.f90 ${depends}
     )