[NFC] PHINode: introduce replaceIncomingBlockWith() function, use it

Summary:
There is `PHINode::getBasicBlockIndex()`, `PHINode::setIncomingBlock()`
and `PHINode::getNumOperands()`, but no function to replace every
specified `BasicBlock*` predecessor with some other specified `BasicBlock*`.
Clearly, there are a lot of places that could use that functionality.

Reviewers: chandlerc, craig.topper, spatel, danielcdh

Reviewed By: craig.topper

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61011

llvm-svn: 359995

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
index 095c82f5c42..b49a91bdc45 100644
--- a/llvm/include/llvm/IR/Instructions.h
+++ b/llvm/include/llvm/IR/Instructions.h
@@ -2738,6 +2738,14 @@ public:
     block_begin()[i] = BB;
   }
 
+  /// Replace every incoming basic block \p Old to basic block \p New.
+  void replaceIncomingBlockWith(BasicBlock *Old, BasicBlock *New) {
+    assert(New && Old && "PHI node got a null basic block!");
+    for (unsigned Op = 0, NumOps = getNumOperands(); Op != NumOps; ++Op)
+      if (getIncomingBlock(Op) == Old)
+        setIncomingBlock(Op, New);
+  }
+
   /// Add an incoming value to the end of the PHI list
   ///
   void addIncoming(Value *V, BasicBlock *BB) {