Be careful with predecessor/successor index.
When we simplify the CFG, we must preserve things that were already
simplified. For example, the index in the predecessor list or
successor list of a block must be preserved for ensuring the
first block is a loop pre header.
bug:21867463
Change-Id: Ic3fcb3eb2c3fb109d8a57ee2a6b6d4d65fdb9410
diff --git a/compiler/optimizing/constant_folding_test.cc b/compiler/optimizing/constant_folding_test.cc
index 422223f..11f6362 100644
--- a/compiler/optimizing/constant_folding_test.cc
+++ b/compiler/optimizing/constant_folding_test.cc
@@ -627,8 +627,8 @@
" 9: If(8)\n"
"BasicBlock 2, pred: 1, succ: 3\n"
" 12: Goto 3\n"
- "BasicBlock 3, pred: 2, 5, succ: 4\n"
- " 22: Phi(3, 5) [15]\n"
+ "BasicBlock 3, pred: 5, 2, succ: 4\n"
+ " 22: Phi(5, 3) [15]\n"
" 15: Add(22, 3)\n"
" 17: ReturnVoid\n"
"BasicBlock 4, pred: 3\n"
diff --git a/compiler/optimizing/dead_code_elimination_test.cc b/compiler/optimizing/dead_code_elimination_test.cc
index 3209d3e..ee3a61a 100644
--- a/compiler/optimizing/dead_code_elimination_test.cc
+++ b/compiler/optimizing/dead_code_elimination_test.cc
@@ -89,8 +89,8 @@
" 9: If(8)\n"
"BasicBlock 2, pred: 1, succ: 3\n"
" 12: Goto 3\n"
- "BasicBlock 3, pred: 2, 5, succ: 4\n"
- " 22: Phi(3, 5) [15]\n"
+ "BasicBlock 3, pred: 5, 2, succ: 4\n"
+ " 22: Phi(5, 3) [15]\n"
" 15: Add(22, 3)\n"
" 17: ReturnVoid\n"
"BasicBlock 4, pred: 3\n"
@@ -101,7 +101,7 @@
// Expected difference after dead code elimination.
diff_t expected_diff = {
{ " 3: IntConstant [15, 22, 8]\n", " 3: IntConstant [22, 8]\n" },
- { " 22: Phi(3, 5) [15]\n", " 22: Phi(3, 5)\n" },
+ { " 22: Phi(5, 3) [15]\n", " 22: Phi(5, 3)\n" },
{ " 15: Add(22, 3)\n", removed }
};
std::string expected_after = Patch(expected_before, expected_diff);
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 68c197e..01eb2d7 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -180,8 +180,9 @@
HBasicBlock* new_block = new (arena_) HBasicBlock(this, successor->GetDexPc());
AddBlock(new_block);
new_block->AddInstruction(new (arena_) HGoto());
- block->ReplaceSuccessor(successor, new_block);
- new_block->AddSuccessor(successor);
+ // Use `InsertBetween` to ensure the predecessor index and successor index of
+ // `block` and `successor` are preserved.
+ new_block->InsertBetween(block, successor);
if (successor->IsLoopHeader()) {
// If we split at a back edge boundary, make the new block the back edge.
HLoopInformation* info = successor->GetLoopInformation();
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 9443653..edd66ec 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -625,6 +625,20 @@
predecessors_.Put(predecessor_index, new_block);
}
+ // Insert `this` between `predecessor` and `successor. This method
+ // preserves the indicies, and will update the first edge found between
+ // `predecessor` and `successor`.
+ void InsertBetween(HBasicBlock* predecessor, HBasicBlock* successor) {
+ size_t predecessor_index = successor->GetPredecessorIndexOf(predecessor);
+ DCHECK_NE(predecessor_index, static_cast<size_t>(-1));
+ size_t successor_index = predecessor->GetSuccessorIndexOf(successor);
+ DCHECK_NE(successor_index, static_cast<size_t>(-1));
+ successor->predecessors_.Put(predecessor_index, this);
+ predecessor->successors_.Put(successor_index, this);
+ successors_.Add(successor);
+ predecessors_.Add(predecessor);
+ }
+
void RemovePredecessor(HBasicBlock* block) {
predecessors_.Delete(block);
}
diff --git a/compiler/optimizing/ssa_test.cc b/compiler/optimizing/ssa_test.cc
index fb3e7d7..0e8c058 100644
--- a/compiler/optimizing/ssa_test.cc
+++ b/compiler/optimizing/ssa_test.cc
@@ -115,7 +115,7 @@
" 3: If(2)\n"
"BasicBlock 2, pred: 1, succ: 3\n"
" 4: Goto\n"
- "BasicBlock 3, pred: 2, 5, succ: 4\n"
+ "BasicBlock 3, pred: 5, 2, succ: 4\n"
" 5: ReturnVoid\n"
"BasicBlock 4, pred: 3\n"
" 6: Exit\n"
@@ -145,8 +145,8 @@
" 4: If(3)\n"
"BasicBlock 2, pred: 1, succ: 3\n"
" 5: Goto\n"
- "BasicBlock 3, pred: 2, 5, succ: 4\n"
- " 6: Phi(1, 0) [7]\n"
+ "BasicBlock 3, pred: 5, 2, succ: 4\n"
+ " 6: Phi(0, 1) [7]\n"
" 7: Return(6)\n"
"BasicBlock 4, pred: 3\n"
" 8: Exit\n"
@@ -428,8 +428,8 @@
" 10: Goto\n"
"BasicBlock 5, pred: 3, succ: 2\n"
" 11: Goto\n"
- "BasicBlock 6, pred: 4, 8, succ: 7\n"
- " 12: Phi(2, 5) [13]\n"
+ "BasicBlock 6, pred: 8, 4, succ: 7\n"
+ " 12: Phi(5, 2) [13]\n"
" 13: Return(12)\n"
"BasicBlock 7, pred: 6\n"
" 14: Exit\n"
@@ -480,7 +480,7 @@
" 4: If(3)\n"
"BasicBlock 2, pred: 1, succ: 3\n"
" 5: Goto\n"
- "BasicBlock 3, pred: 2, 5, succ: 4\n"
+ "BasicBlock 3, pred: 5, 2, succ: 4\n"
" 6: ReturnVoid\n"
"BasicBlock 4, pred: 3\n"
" 7: Exit\n"
@@ -517,7 +517,7 @@
" 8: Add(0, 0)\n"
" 9: Goto\n"
// This block should not get a phi for local 1.
- "BasicBlock 5, pred: 2, 4, 7, succ: 6\n"
+ "BasicBlock 5, pred: 2, 7, 4, succ: 6\n"
" 10: ReturnVoid\n"
"BasicBlock 6, pred: 5\n"
" 11: Exit\n"