Support non-fallthrough unconditional branches in FastISel.

llvm-svn: 55191

2 files changed, 17 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 1462472ea4a..74174519fb3 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -145,6 +145,8 @@ BasicBlock::iterator
 FastISel::SelectInstructions(BasicBlock::iterator Begin,
                              BasicBlock::iterator End,
                              DenseMap<const Value*, unsigned> &ValueMap,
+                             std::map<const BasicBlock*,
+                                      MachineBasicBlock *> &MBBMap,
                              MachineBasicBlock *mbb) {
   MBB = mbb;
   BasicBlock::iterator I = Begin;
@@ -195,19 +197,25 @@ FastISel::SelectInstructions(BasicBlock::iterator Begin,
     case Instruction::Br: {
       BranchInst *BI = cast<BranchInst>(I);
 
-      // For now, check for and handle just the most trivial case: an
-      // unconditional fall-through branch.
       if (BI->isUnconditional()) {
-         MachineFunction::iterator NextMBB =
+        MachineFunction::iterator NextMBB =
            next(MachineFunction::iterator(MBB));
-         if (NextMBB != MF.end() &&
-             NextMBB->getBasicBlock() == BI->getSuccessor(0)) {
-          MBB->addSuccessor(NextMBB);
-          break;
+        BasicBlock *LLVMSucc = BI->getSuccessor(0);
+        MachineBasicBlock *MSucc = MBBMap[LLVMSucc];
+
+        if (NextMBB != MF.end() && MSucc == NextMBB) {
+          // The unconditional fall-through case, which needs no instructions.
+        } else {
+          // The unconditional branch case.
+          const SmallVector<MachineOperand, 0> NoCond(0);
+          TII.InsertBranch(*MBB, MSucc, NULL, NoCond);
         }
+        MBB->addSuccessor(MSucc);
+        break;
       }
 
-      // Something more complicated. Halt "fast" selection and bail.
+      // Conditional branches are not handed yet.
+      // Halt "fast" selection and bail.
       return I;
     }
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 9304c0e7a16..e13cfc0fa03 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -5113,7 +5113,7 @@ void SelectionDAGISel::BuildSelectionDAG(SelectionDAG &DAG, BasicBlock *LLVMBB,
       cast<BranchInst>(LLVMBB->getTerminator())->isUnconditional()) {
     if (FastISel *F = TLI.createFastISel(FuncInfo.MF)) {
       Begin = F->SelectInstructions(Begin, LLVMBB->end(),
-                                    FuncInfo.ValueMap, BB);
+                                    FuncInfo.ValueMap, FuncInfo.MBBMap, BB);
 
       // Clean up the FastISel object. TODO: Reorganize what data is
       // stored in the FastISel class itself and what is merely passed