[clang] Use VFS for -fopenmp-host-ir-file-path (llvm#156727)

This is a follow-up to llvm#150124. This PR makes it so that the
`-fopenmp-host-ir-file-path` respects VFS overlays, like any other input
file.

(cherry picked from commit d1c0b1b)

Author: jansvoboda11

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -1038,7 +1038,8 @@ CGOpenMPRuntime::CGOpenMPRuntime(CodeGenModule &CGM)
       /*HasRequiresReverseOffload*/ false, /*HasRequiresUnifiedAddress*/ false,
       hasRequiresUnifiedSharedMemory(), /*HasRequiresDynamicAllocators*/ false);
   OMPBuilder.initialize();
-  OMPBuilder.loadOffloadInfoMetadata(CGM.getLangOpts().OpenMPIsTargetDevice
+  OMPBuilder.loadOffloadInfoMetadata(*CGM.getFileSystem(),
+                                     CGM.getLangOpts().OpenMPIsTargetDevice
                                          ? CGM.getLangOpts().OMPHostIRFile
                                          : StringRef{});
   OMPBuilder.setConfig(Config);

clang/lib/CodeGen/CodeGenModule.cpp

@@ -588,8 +588,7 @@ void CodeGenModule::createOpenCLRuntime() {
 }
 
 void CodeGenModule::createOpenMPRuntime() {
-  if (!LangOpts.OMPHostIRFile.empty() &&
-      !llvm::sys::fs::exists(LangOpts.OMPHostIRFile))
+  if (!LangOpts.OMPHostIRFile.empty() && !FS->exists(LangOpts.OMPHostIRFile))
     Diags.Report(diag::err_omp_host_ir_file_not_found)
         << LangOpts.OMPHostIRFile;
 

clang/test/OpenMP/host-ir-file-vfs.c

@@ -0,0 +1,33 @@
+// This test checks that the OpenMP host IR file goes through VFS overlays.
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+// RUN: sed -e "s|DIR|%/t|g" %t/vfs.json.in > %t/vfs.json
+// RUN: %clang_cc1 -fopenmp-simd -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-llvm-bc %t/host.c -o %t/host.bc
+
+// RUN: %clang_cc1 -fopenmp-simd -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-llvm %t/device.c -o - \
+// RUN:   -fopenmp-is-target-device -fopenmp-host-ir-file-path %t/virtual/host.bc -ivfsoverlay %t/vfs.json -verify
+
+//--- vfs.json.in
+{
+  'version': 0,
+  'use-external-names': true,
+  'roots': [
+    {
+      'name': 'DIR/virtual',
+      'type': 'directory',
+      'contents': [
+        {
+          'name': 'host.bc',
+          'type': 'file',
+          'external-contents': 'DIR/host.bc'
+        }
+      ]
+    }
+  ]
+}
+
+//--- host.c
+//--- device.c
+// expected-no-diagnostics

llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h

@@ -38,6 +38,10 @@ class Loop;
 class LoopAnalysis;
 class LoopInfo;
 
+namespace vfs {
+class FileSystem;
+} // namespace vfs
+
 /// Move the instruction after an InsertPoint to the beginning of another
 /// BasicBlock.
 ///
@@ -3491,7 +3495,8 @@ class OpenMPIRBuilder {
   /// \param HostFilePath The path to the host IR file,
   /// used to load in offload metadata for the device, allowing host and device
   /// to maintain the same metadata mapping.
-  LLVM_ABI void loadOffloadInfoMetadata(StringRef HostFilePath);
+  LLVM_ABI void loadOffloadInfoMetadata(vfs::FileSystem &VFS,
+                                        StringRef HostFilePath);
 
   /// Gets (if variable with the given name already exist) or creates
   /// internal global variable with the specified Name. The created variable has

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -51,6 +51,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
@@ -10083,11 +10084,12 @@ void OpenMPIRBuilder::loadOffloadInfoMetadata(Module &M) {
   }
 }
 
-void OpenMPIRBuilder::loadOffloadInfoMetadata(StringRef HostFilePath) {
+void OpenMPIRBuilder::loadOffloadInfoMetadata(vfs::FileSystem &VFS,
+                                              StringRef HostFilePath) {
   if (HostFilePath.empty())
     return;
 
-  auto Buf = MemoryBuffer::getFile(HostFilePath);
+  auto Buf = VFS.getBufferForFile(HostFilePath);
   if (std::error_code Err = Buf.getError()) {
     report_fatal_error(("error opening host file from host file path inside of "
                         "OpenMPIRBuilder: " +

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -36,6 +36,7 @@
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/ReplaceConstant.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TargetParser/Triple.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 
@@ -6185,7 +6186,9 @@ LogicalResult OpenMPDialectLLVMIRTranslationInterface::amendOperation(
               if (auto filepathAttr = dyn_cast<StringAttr>(attr)) {
                 llvm::OpenMPIRBuilder *ompBuilder =
                     moduleTranslation.getOpenMPBuilder();
-                ompBuilder->loadOffloadInfoMetadata(filepathAttr.getValue());
+                auto VFS = llvm::vfs::getRealFileSystem();
+                ompBuilder->loadOffloadInfoMetadata(*VFS,
+                                                    filepathAttr.getValue());
                 return success();
               }
               return failure();