From db51efb3617d15f1cd9e5ff0cc2d934777014e9a Mon Sep 17 00:00:00 2001 From: David Brazdil Date: Fri, 6 Nov 2015 01:36:20 +0000 Subject: ART: Fix critical edge splitting under try/catch A critical edge would not be split if the predecessor ends with TryBoundary. This would eventually trip liveness analysis because a back edge block would have smaller liveness position than a nested loop. Another implication of this change is that an edge between a loop's pre-header ending with TryBoundary and the header will be split, guaranteeing that a pre-header always has just one successor. Bug: 25493695 Bug: 25454012 Change-Id: I5a13b8bb74509b48f5d628906f7158af007f99ae --- compiler/optimizing/nodes.cc | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) (limited to 'compiler/optimizing/nodes.cc') diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc index af3d8f4a60..3e137ff17c 100644 --- a/compiler/optimizing/nodes.cc +++ b/compiler/optimizing/nodes.cc @@ -383,19 +383,27 @@ void HGraph::ComputeTryBlockInformation() { } void HGraph::SimplifyCFG() { - // Simplify the CFG for future analysis, and code generation: +// Simplify the CFG for future analysis, and code generation: // (1): Split critical edges. - // (2): Simplify loops by having only one back edge, and one preheader. + // (2): Simplify loops by having only one preheader. // NOTE: We're appending new blocks inside the loop, so we need to use index because iterators // can be invalidated. We remember the initial size to avoid iterating over the new blocks. for (size_t block_id = 0u, end = blocks_.size(); block_id != end; ++block_id) { HBasicBlock* block = blocks_[block_id]; if (block == nullptr) continue; - if (block->NumberOfNormalSuccessors() > 1) { - for (size_t j = 0; j < block->GetSuccessors().size(); ++j) { + if (block->GetSuccessors().size() > 1) { + // Only split normal-flow edges. We cannot split exceptional edges as they + // are synthesized (approximate real control flow), and we do not need to + // anyway. Moves that would be inserted there are performed by the runtime. + for (size_t j = 0, e = block->NumberOfNormalSuccessors(); j < e; ++j) { HBasicBlock* successor = block->GetSuccessors()[j]; DCHECK(!successor->IsCatchBlock()); - if (successor->GetPredecessors().size() > 1) { + if (successor == exit_block_) { + // Throw->TryBoundary->Exit. Special case which we do not want to split + // because Goto->Exit is not allowed. + DCHECK(block->IsSingleTryBoundary()); + DCHECK(block->GetSinglePredecessor()->GetLastInstruction()->IsThrow()); + } else if (successor->GetPredecessors().size() > 1) { SplitCriticalEdge(block, successor); --j; } -- cgit v1.2.3-59-g8ed1b