From 179481419851ca4bd3643dc89d3d83056246c4a8 Mon Sep 17 00:00:00 2001 From: Evgeniy Stepanov Date: Mon, 17 Dec 2012 14:28:00 +0000 Subject: [PATCH] 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 --- lib/Transforms/Scalar/SimplifyCFGPass.cpp | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp index 9160f04fe22..3af62ebcef1 100644 --- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp +++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp @@ -111,13 +111,11 @@ static bool markAliveBlocks(BasicBlock *BB, SmallVector 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 @@ static bool markAliveBlocks(BasicBlock *BB, 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; }