Quick: Fix optimizations for empty if blocks.
If a block ending with if-eqz or if-nez has the same "taken"
and "fallthrough", we cannot assume that the value has been
checked against zero in one of the succesors. This affects
the null check elimination pass as well as GVN. Refactor all
those checks to a single function in BasicBlock and check
that the "taken" and "falthrough" are different when needed.
Bug: 21614284
Change-Id: I8c6ac23e96cdaf5984786a555ebbd28110f095cb
diff --git a/compiler/dex/global_value_numbering.cc b/compiler/dex/global_value_numbering.cc
index e2b9987..94ba4fa 100644
--- a/compiler/dex/global_value_numbering.cc
+++ b/compiler/dex/global_value_numbering.cc
@@ -160,20 +160,10 @@
return location;
}
-bool GlobalValueNumbering::HasNullCheckLastInsn(const BasicBlock* pred_bb,
- BasicBlockId succ_id) {
- if (pred_bb->block_type != kDalvikByteCode || pred_bb->last_mir_insn == nullptr) {
- return false;
- }
- Instruction::Code last_opcode = pred_bb->last_mir_insn->dalvikInsn.opcode;
- return ((last_opcode == Instruction::IF_EQZ && pred_bb->fall_through == succ_id) ||
- (last_opcode == Instruction::IF_NEZ && pred_bb->taken == succ_id));
-}
-
bool GlobalValueNumbering::NullCheckedInAllPredecessors(
const ScopedArenaVector<uint16_t>& merge_names) const {
// Implicit parameters:
- // - *work_lvn: the LVN for which we're checking predecessors.
+ // - *work_lvn_: the LVN for which we're checking predecessors.
// - merge_lvns_: the predecessor LVNs.
DCHECK_EQ(merge_lvns_.size(), merge_names.size());
for (size_t i = 0, size = merge_lvns_.size(); i != size; ++i) {
@@ -198,7 +188,7 @@
bool GlobalValueNumbering::DivZeroCheckedInAllPredecessors(
const ScopedArenaVector<uint16_t>& merge_names) const {
// Implicit parameters:
- // - *work_lvn: the LVN for which we're checking predecessors.
+ // - *work_lvn_: the LVN for which we're checking predecessors.
// - merge_lvns_: the predecessor LVNs.
DCHECK_EQ(merge_lvns_.size(), merge_names.size());
for (size_t i = 0, size = merge_lvns_.size(); i != size; ++i) {
@@ -217,15 +207,11 @@
if (bb->predecessors.size() == 1u) {
BasicBlockId pred_id = bb->predecessors[0];
BasicBlock* pred_bb = mir_graph_->GetBasicBlock(pred_id);
- if (pred_bb->last_mir_insn != nullptr) {
- Instruction::Code opcode = pred_bb->last_mir_insn->dalvikInsn.opcode;
- if ((opcode == Instruction::IF_NEZ && pred_bb->taken == bb_id) ||
- (opcode == Instruction::IF_EQZ && pred_bb->fall_through == bb_id)) {
- DCHECK(lvns_[pred_id] != nullptr);
- uint16_t operand = lvns_[pred_id]->GetSregValue(pred_bb->last_mir_insn->ssa_rep->uses[0]);
- if (operand == cond) {
- return true;
- }
+ if (pred_bb->BranchesToSuccessorOnlyIfNotZero(bb_id)) {
+ DCHECK(lvns_[pred_id] != nullptr);
+ uint16_t operand = lvns_[pred_id]->GetSregValue(pred_bb->last_mir_insn->ssa_rep->uses[0]);
+ if (operand == cond) {
+ return true;
}
}
}