In BasicBlock::splitBasicBlock, just use islist::splice to move the instructions,

instead of a loop that is really inefficient with large basic blocks.

This speeds up the inliner pass on the testcase in PR209 from 13.8s to 2.24s
which still isn't exactly speedy, but is a lot better.  :)

llvm-svn: 11105

1 files changed, 3 insertions, 8 deletions

diff --git a/llvm/lib/VMCore/BasicBlock.cpp b/llvm/lib/VMCore/BasicBlock.cpp
index f2b551bbd90..c83b316672c 100644
--- a/llvm/lib/VMCore/BasicBlock.cpp
+++ b/llvm/lib/VMCore/BasicBlock.cpp
@@ -233,14 +233,9 @@ BasicBlock *BasicBlock::splitBasicBlock(iterator I, const std::string &BBName) {
 
   BasicBlock *New = new BasicBlock(BBName, getParent());
 
-  // Go from the end of the basic block through to the iterator pointer, moving
-  // to the new basic block...
-  Instruction *Inst = 0;
-  do {
-    iterator EndIt = end();
-    Inst = InstList.remove(--EndIt);                  // Remove from end
-    New->InstList.push_front(Inst);                   // Add to front
-  } while (Inst != &*I);   // Loop until we move the specified instruction.
+  // Move all of the specified instructions from the original basic block into
+  // the new basic block.
+  New->getInstList().splice(New->end(), this->getInstList(), I, end());
 
   // Add a branch instruction to the newly formed basic block.
   new BranchInst(New, this);