Initial code to convert ResumeInsts into calls to _Unwind_Resume.

This should be the only code necessary for DWARF EH prepare.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136387 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 57 insertions, 1 deletions

diff --git a/lib/CodeGen/DwarfEHPrepare.cpp b/lib/CodeGen/DwarfEHPrepare.cpp
index 03604b0a17..3aa72ee196 100644
--- a/lib/CodeGen/DwarfEHPrepare.cpp
+++ b/lib/CodeGen/DwarfEHPrepare.cpp
@@ -63,6 +63,8 @@ namespace {
     typedef SmallPtrSet<BasicBlock*, 8> BBSet;
     BBSet LandingPads;
 
+    bool InsertUnwindResumeCalls();
+
     bool NormalizeLandingPads();
     bool LowerUnwindsAndResumes();
     bool MoveExceptionValueCalls();
@@ -658,13 +660,67 @@ Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
   return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
 }
 
+/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
+/// into calls to the appropriate _Unwind_Resume function.
+bool DwarfEHPrepare::InsertUnwindResumeCalls() {
+  SmallVector<ResumeInst*, 16> Resumes;
+  for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
+    for (BasicBlock::iterator II = I->begin(), IE = I->end(); II != IE; ++II)
+      if (ResumeInst *RI = dyn_cast<ResumeInst>(II))
+        Resumes.push_back(RI);
+
+  if (Resumes.empty())
+    return false;
+
+  // Find the rewind function if we didn't already.
+  if (!RewindFunction) {
+    LLVMContext &Ctx = Resumes[0]->getContext();
+    FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
+                                          Type::getInt8PtrTy(Ctx), false);
+    const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
+    RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
+  }
+
+  // Create the basic block where the _Unwind_Resume call will live.
+  LLVMContext &Ctx = F->getContext();
+  BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", F);
+  PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), Resumes.size(),
+                                "exn.obj", UnwindBB);
+
+  // Extract the exception object from the ResumeInst and add it to the PHI node
+  // that feeds the _Unwind_Resume call.
+  for (SmallVectorImpl<ResumeInst*>::iterator
+         I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
+    ResumeInst *RI = *I;
+    BranchInst::Create(UnwindBB, RI->getParent());
+    ExtractValueInst *ExnObj = ExtractValueInst::Create(RI->getOperand(0),
+                                                        0, "exn.obj", RI);
+    PN->addIncoming(ExnObj, RI->getParent());
+    RI->eraseFromParent();
+  }
+
+  // Call the function.
+  CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
+  CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
+
+  // We never expect _Unwind_Resume to return.
+  new UnreachableInst(Ctx, UnwindBB);
+  return true;
+}
+
 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
   bool Changed = false;
 
   // Initialize internal state.
-  DT = &getAnalysis<DominatorTree>();
+  DT = &getAnalysis<DominatorTree>(); // FIXME: We won't need this with the new EH.
   F = &Fn;
 
+  if (InsertUnwindResumeCalls()) {
+    // FIXME: The reset of this function can go once the new EH is done.
+    LandingPads.clear();
+    return true;
+  }
+
   // Ensure that only unwind edges end at landing pads (a landing pad is a
   // basic block where an invoke unwind edge ends).
   Changed |= NormalizeLandingPads();