[PATCH] MIR Serialization: Create dummy functions for the parsed machine functions when MIR file doesn't contain LLVM IR.

[Alex Lorenz]

Hi dexonsmith, bogner, bob.wilson,

This patch is based on the patch that connects MIRParser to the machine function analysis pass (http://reviews.llvm.org/D9928).

This patch creates dummy LLVM functions with one basic block and a return instruction for the parsed machine functions when the MIR file doesn't include LLVM IR.
This is needed as the machine function analysis pass creates machine functions only for the functions defined in the current LLVM module.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D10135

Files:
  lib/CodeGen/MIRParser/MIRParser.cpp
  test/CodeGen/MIR/llvmIRMissing.mir

Index: lib/CodeGen/MIRParser/MIRParser.cpp
===================================================================
--- lib/CodeGen/MIRParser/MIRParser.cpp
+++ lib/CodeGen/MIRParser/MIRParser.cpp
@@ -19,6 +19,7 @@
 #include "llvm/AsmParser/Parser.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MIRYamlMapping.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/SourceMgr.h"
@@ -51,13 +52,17 @@
   /// Parse the machine function in the current YAML document.
   ///
   /// Return true if an error occurred.
-  bool parseMachineFunction(yaml::Input &In);
+  bool parseMachineFunction(yaml::Input &In, Module &M, bool NoLLVMIR);
 
   /// Initialize the machine function to the state that's described in the MIR
   /// file.
   ///
   /// Return true if error occurred.
   bool initializeMachineFunction(MachineFunction &MF, SMDiagnostic &Error);
+
+private:
+  /// Create an empty function with the given name.
+  void createDummyFunction(StringRef Name, Module &M);
 };
 
 } // end namespace llvm
@@ -84,6 +89,7 @@
   }
 
   std::unique_ptr<Module> M;
+  bool NoLLVMIR = false;
   // Parse the block scalar manually so that we can return unique pointer
   // without having to go trough YAML traits.
   if (const auto *BSN =
@@ -98,28 +104,40 @@
   } else {
     // Create an new, empty module.
     M = llvm::make_unique<Module>(Filename, Context);
+    NoLLVMIR = true;
   }
 
   // Parse the machine functions.
   do {
-    if (parseMachineFunction(In))
+    if (parseMachineFunction(In, *M, NoLLVMIR))
       return nullptr;
     In.nextDocument();
   } while (In.setCurrentDocument());
 
   return M;
 }
 
-bool MIRParserImpl::parseMachineFunction(yaml::Input &In) {
+bool MIRParserImpl::parseMachineFunction(yaml::Input &In, Module &M,
+                                         bool NoLLVMIR) {
   auto MF = llvm::make_unique<yaml::MachineFunction>();
   yaml::yamlize(In, *MF, false);
   if (In.error())
     return true;
   auto FunctionName = MF->Name;
   Functions.insert(std::make_pair(FunctionName, std::move(MF)));
+  if (NoLLVMIR)
+    createDummyFunction(FunctionName, M);
   return false;
 }
 
+void MIRParserImpl::createDummyFunction(StringRef Name, Module &M) {
+  auto &Context = M.getContext();
+  Function *F = cast<Function>(M.getOrInsertFunction(
+      Name, FunctionType::get(Type::getVoidTy(Context), false)));
+  BasicBlock *BB = BasicBlock::Create(Context, "Entry", F);
+  ReturnInst::Create(Context, nullptr, BB);
+}
+
 bool MIRParserImpl::initializeMachineFunction(MachineFunction &MF,
                                               SMDiagnostic &Error) {
   auto It = Functions.find(MF.getName());
Index: test/CodeGen/MIR/llvmIRMissing.mir
===================================================================
--- test/CodeGen/MIR/llvmIRMissing.mir
+++ test/CodeGen/MIR/llvmIRMissing.mir
@@ -1,5 +1,7 @@
-# RUN: llc -start-after branch-folder -stop-after branch-folder -o /dev/null %s
+# RUN: llc -start-after branch-folder -stop-after branch-folder -o /dev/null %s | FileCheck %s
 # This test ensures that the MIR parser accepts files without the LLVM IR.
 
 ---
+# CHECK: name: foo
+name: foo
 ...

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