Pass -backend-option to LLVM when there is no target machine

[yaxunl]

Summary

Clang should pass -backend-option to LLVM even though there is no target machine, since LLVM passes are used when emitting LLVM IR.

Differential Revision: http://reviews.llvm.org/D17552

[yaxunl]

Hi Anastasia/Richard,

I found this issue when investigating some codegen issues in Clang -cc1 with -emit-llvm. I need to pass an llvm option -print-after-all to the LLVM pass manager which is used to run the optimization passes before emitting llvm. However it did not work. Then I found ParseCommandLineOptions was only called when target machine was set. I fixed this by always call ParseCommandLineOptions even though there is no target machine.

This bug causes difficulty for OpenCL since it is usually compiled without target machine.

Could you please review this? Thanks.

[• tstellarAMD]

Do you have a test case for this?

[yaxunl]

Add a test for -backend-option with and w/o target machine as suggested by Tom.

[rsmith]

LGTM

[Anastasia]

LGTM, apart from small remark on the test!

test/Frontend/backend-option.c

2 ↗

(On Diff #49781)

I think conceptually it's not correct to pass spir target with C module, although it doesn't make any difference here for this test. I would still change it to some x86 one.

[yaxunl]

test/Frontend/backend-option.c

2 ↗

(On Diff #49781)

if we change it to x86, it has a target machine, so the test no longer reproduce the original issue.

How about add -x cl for the second command to force the source to be treated as cl source code, then it can reproduce the original issue and at the same time is valid for spir target?

[Anastasia]

test/Frontend/backend-option.c

2 ↗

(On Diff #49781)

Sure!

[yaxunl]

Add -x cl to the test when compiling it for spir target.

[yaxunl]

Ping. Tom, are you OK with this fix?

lib/CodeGen/BackendUtil.cpp

     return PerFunctionPasses;
   }
 
+  /// Set LLVM command line options passed through -backend-option.
+  void setCommandLineOpts();
+
   void CreatePasses(FunctionInfoIndex *FunctionIndex);
 
   /// Generates the TargetMachine.

   PMBuilder.populateModulePassManager(*MPM);
 }
 
+void EmitAssemblyHelper::setCommandLineOpts() {
+  SmallVector<const char *, 16> BackendArgs;
+  BackendArgs.push_back("clang"); // Fake program name.
+  if (!CodeGenOpts.DebugPass.empty()) {
+    BackendArgs.push_back("-debug-pass");
+    BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
+  }
+  if (!CodeGenOpts.LimitFloatPrecision.empty()) {
+    BackendArgs.push_back("-limit-float-precision");
+    BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
+  }
+  for (const std::string &BackendOption : CodeGenOpts.BackendOptions)
+    BackendArgs.push_back(BackendOption.c_str());
+  BackendArgs.push_back(nullptr);
+  llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
+                                    BackendArgs.data());
+}
+
 TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
   // Create the TargetMachine for generating code.
   std::string Error;

   assert(CodeModel != ~0u && "invalid code model!");
   llvm::CodeModel::Model CM = static_cast<llvm::CodeModel::Model>(CodeModel);
 
-  SmallVector<const char *, 16> BackendArgs;
-  BackendArgs.push_back("clang"); // Fake program name.
-  if (!CodeGenOpts.DebugPass.empty()) {
-    BackendArgs.push_back("-debug-pass");
-    BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
-  }
-  if (!CodeGenOpts.LimitFloatPrecision.empty()) {
-    BackendArgs.push_back("-limit-float-precision");
-    BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
-  }
-  for (const std::string &BackendOption : CodeGenOpts.BackendOptions)
-    BackendArgs.push_back(BackendOption.c_str());
-  BackendArgs.push_back(nullptr);
-  llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
-                                    BackendArgs.data());
-
   std::string FeaturesStr =
       llvm::join(TargetOpts.Features.begin(), TargetOpts.Features.end(), ",");
 

                                       raw_pwrite_stream *OS) {
   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : nullptr);
 
+  setCommandLineOpts();
+
   bool UsesCodeGen = (Action != Backend_EmitNothing &&
                       Action != Backend_EmitBC &&
                       Action != Backend_EmitLL);