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author | Nicolas Geoffray <ngeoffray@google.com> | 2014-06-04 12:12:08 +0100 |
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committer | Nicolas Geoffray <ngeoffray@google.com> | 2014-06-04 13:39:37 +0100 |
commit | 7c3560f2ce0ec9484004d05a94bfaa6e02f5a96a (patch) | |
tree | 44544a733178fe7416264e064477c681f08ae562 /compiler/optimizing/ssa_builder.cc | |
parent | 57795db7d44bcd6d106481fa192691400b2358c8 (diff) | |
download | art-7c3560f2ce0ec9484004d05a94bfaa6e02f5a96a.zip art-7c3560f2ce0ec9484004d05a94bfaa6e02f5a96a.tar.gz art-7c3560f2ce0ec9484004d05a94bfaa6e02f5a96a.tar.bz2 |
Fix a bug in SSA construction.
If a join block does not have an incoming value for a local
from a predecessor block, we should not create a phi. The
verifier has made sure the local is updated before any
following reads after this block.
Change-Id: Id2785efc73c9fb3224826fff2f4b4ad215905ff4
Diffstat (limited to 'compiler/optimizing/ssa_builder.cc')
-rw-r--r-- | compiler/optimizing/ssa_builder.cc | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/compiler/optimizing/ssa_builder.cc b/compiler/optimizing/ssa_builder.cc index 33084df..1284a97 100644 --- a/compiler/optimizing/ssa_builder.cc +++ b/compiler/optimizing/ssa_builder.cc @@ -95,14 +95,26 @@ void SsaBuilder::VisitBasicBlock(HBasicBlock* block) { // All predecessors have already been visited because we are visiting in reverse post order. // We merge the values of all locals, creating phis if those values differ. for (size_t local = 0; local < current_locals_->Size(); local++) { + bool one_predecessor_has_no_value = false; bool is_different = false; HInstruction* value = ValueOfLocal(block->GetPredecessors().Get(0), local); - for (size_t i = 1; i < block->GetPredecessors().Size(); i++) { - if (ValueOfLocal(block->GetPredecessors().Get(i), local) != value) { + + for (size_t i = 0, e = block->GetPredecessors().Size(); i < e; ++i) { + HInstruction* current = ValueOfLocal(block->GetPredecessors().Get(i), local); + if (current == nullptr) { +// one_predecessor_has_no_value = true; +// break; + } else if (current != value) { is_different = true; - break; } } + + if (one_predecessor_has_no_value) { + // If one predecessor has no value for this local, we trust the verifier has + // successfully checked that there is a store dominating any read after this block. + continue; + } + if (is_different) { HPhi* phi = new (GetGraph()->GetArena()) HPhi( GetGraph()->GetArena(), local, block->GetPredecessors().Size(), Primitive::kPrimVoid); |