MIR Serialization: Create dummy functions when the MIR file doesn't have LLVM IR.

This commit creates a dummy LLVM IR function with one basic block and an unreachable
instruction for each parsed machine function when the MIR file doesn't have LLVM IR.
This change is required as the machine function analysis pass creates machine
functions only for the functions that are defined in the current LLVM module.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10135


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239778 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MIRParser/MIRParser.cpp

@@ -20,6 +20,7 @@
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MIRYamlMapping.h"
 #include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/LineIterator.h"
@@ -60,8 +61,12 @@ public:
 
   /// Parse the machine function in the current YAML document.
   ///
+  /// \param NoLLVMIR - set to true when the MIR file doesn't have LLVM IR.
+  /// A dummy IR function is created and inserted into the given module when
+  /// this parameter is true.
+  ///
   /// 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.
@@ -73,6 +78,9 @@ private:
   /// Return a MIR diagnostic converted from an LLVM assembly diagnostic.
   SMDiagnostic diagFromLLVMAssemblyDiag(const SMDiagnostic &Error,
                                         SMRange SourceRange);
+
+  /// Create an empty function with the given name.
+  void createDummyFunction(StringRef Name, Module &M);
 };
 
 } // end namespace llvm
@@ -121,6 +129,7 @@ std::unique_ptr<Module> MIRParserImpl::parse() {
   }
 
   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 =
@@ -138,11 +147,12 @@ std::unique_ptr<Module> MIRParserImpl::parse() {
   } 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());
@@ -150,7 +160,8 @@ std::unique_ptr<Module> MIRParserImpl::parse() {
   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())
@@ -160,9 +171,19 @@ bool MIRParserImpl::parseMachineFunction(yaml::Input &In) {
     return error(Twine("redefinition of machine function '") + FunctionName +
                  "'");
   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);
+  new UnreachableInst(Context, BB);
+}
+
 bool MIRParserImpl::initializeMachineFunction(MachineFunction &MF) {
   auto It = Functions.find(MF.getName());
   if (It == Functions.end())

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
 ...