Add MachineBasicBlock::isPredecessor().

A->isPredecessor(B) is the same as B->isSuccessor(A), but it can
tolerate a B that is null or dangling. This shouldn't happen normally,
but it it useful for verification code.

llvm-svn: 160968

2 files changed, 9 insertions, 2 deletions

diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 4371aa5261d..c917bd8b818 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -379,6 +379,10 @@ public:
   /// which refer to fromMBB to refer to this.
   void transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB);
 
+  /// isPredecessor - Return true if the specified MBB is a predecessor of this
+  /// block.
+  bool isPredecessor(const MachineBasicBlock *MBB) const;
+
   /// isSuccessor - Return true if the specified MBB is a successor of this
   /// block.
   bool isSuccessor(const MachineBasicBlock *MBB) const;
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index ecc1e951fad..f361d1ac293 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -540,9 +540,12 @@ MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
   }
 }
 
+bool MachineBasicBlock::isPredecessor(const MachineBasicBlock *MBB) const {
+  return std::find(pred_begin(), pred_end(), MBB) != pred_end();
+}
+
 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
-  const_succ_iterator I = std::find(Successors.begin(), Successors.end(), MBB);
-  return I != Successors.end();
+  return std::find(succ_begin(), succ_end(), MBB) != succ_end();
 }
 
 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {