Optimize tree walking in markAliveBlocks.
Check whether a BB is known as reachable before adding it to the worklist.
This way BB's with multiple predecessors are added to the list no more than
once.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170335 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index 9160f04..3af62eb 100644
--- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -111,13 +111,11 @@
SmallVector<BasicBlock*, 128> Worklist;
Worklist.push_back(BB);
+ Reachable.insert(BB);
bool Changed = false;
do {
BB = Worklist.pop_back_val();
- if (!Reachable.insert(BB))
- continue;
-
// Do a quick scan of the basic block, turning any obviously unreachable
// instructions into LLVM unreachable insts. The instruction combining pass
// canonicalizes unreachable insts into stores to null or undef.
@@ -176,7 +174,8 @@
Changed |= ConstantFoldTerminator(BB, true);
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- Worklist.push_back(*SI);
+ if (Reachable.insert(*SI))
+ Worklist.push_back(*SI);
} while (!Worklist.empty());
return Changed;
}