From 4e467043fbb5fc9c7c426019c40f9db85d84f31f Mon Sep 17 00:00:00 2001 From: Brian Gesiak Date: Thu, 7 Mar 2019 20:40:55 +0000 Subject: [PATCH] [CodeGen] Reuse BlockUtils for -unreachableblockelim pass (NFC) Summary: The logic in the -unreachableblockelim pass does the following: 1. It traverses the function it's given in depth-first order and creates a set of basic blocks that are unreachable from the function's entry node. 2. It iterates over each of those unreachable blocks and (1) removes any successors' references to the dead block, and (2) replaces any uses of instructions from the dead block with null. The logic in (2) above is identical to what the `llvm::DeleteDeadBlocks` function from `BasicBlockUtils.h` does. The only difference is that `llvm::DeleteDeadBlocks` replaces uses of instructions from dead blocks not with null, but with undef. Replace the duplicate logic in the -unreachableblockelim pass with a call to `llvm::DeleteDeadBlocks`. This results in less code but no functional change (NFC). Reviewers: mkazantsev, wmi, davidxl, silvas, davide Reviewed By: davide Subscribers: llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D59064 llvm-svn: 355634 --- llvm/lib/CodeGen/UnreachableBlockElim.cpp | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) diff --git a/llvm/lib/CodeGen/UnreachableBlockElim.cpp b/llvm/lib/CodeGen/UnreachableBlockElim.cpp index 9da7eb3..57e548c 100644 --- a/llvm/lib/CodeGen/UnreachableBlockElim.cpp +++ b/llvm/lib/CodeGen/UnreachableBlockElim.cpp @@ -37,6 +37,7 @@ #include "llvm/IR/Instructions.h" #include "llvm/IR/Type.h" #include "llvm/Pass.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" using namespace llvm; static bool eliminateUnreachableBlock(Function &F) { @@ -46,26 +47,16 @@ static bool eliminateUnreachableBlock(Function &F) { for (BasicBlock *BB : depth_first_ext(&F, Reachable)) (void)BB/* Mark all reachable blocks */; - // Loop over all dead blocks, remembering them and deleting all instructions - // in them. + // Collect all dead blocks. std::vector DeadBlocks; for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) if (!Reachable.count(&*I)) { BasicBlock *BB = &*I; DeadBlocks.push_back(BB); - while (PHINode *PN = dyn_cast(BB->begin())) { - PN->replaceAllUsesWith(Constant::getNullValue(PN->getType())); - BB->getInstList().pop_front(); - } - for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) - (*SI)->removePredecessor(BB); - BB->dropAllReferences(); } - // Actually remove the blocks now. - for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i) { - DeadBlocks[i]->eraseFromParent(); - } + // Delete the dead blocks. + DeleteDeadBlocks(DeadBlocks); return !DeadBlocks.empty(); } -- 2.7.4