Remove instructions from dead blocks when building the dominator tree

We now remove the instructions to free up memory. We have to refactor
methods a little bit to avoid removing instructions as users twice,
since we do not support that.

Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Change-Id: Ia34c4a6af204952d295e5a2cb534115ced97ab07

1 files changed, 8 insertions, 5 deletions

diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 103d318710..98bcd38609 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -1351,11 +1351,14 @@ class HBasicBlock : public ArenaObject<kArenaAllocBasicBlock> {
   // skip updating those phis.
   void DisconnectFromSuccessors(const ArenaBitVector* visited = nullptr);
 
-  // Removes the catch phi uses of the instructions in `this`. If `remove_instruction` is set to
-  // true, it will also remove the instructions themselves. This method assumes the instructions
-  // have been removed from all users with the exception of catch phis because of missing
-  // exceptional edges in the graph.
-  void RemoveCatchPhiUses(bool remove_instruction);
+  // Removes the catch phi uses of the instructions in `this`, and then remove the instruction
+  // itself. If `building_dominator_tree` is true, it will not remove the instruction as user, since
+  // we do it in a previous step. This is a special case for building up the dominator tree: we want
+  // to eliminate uses before inputs but we don't have domination information, so we remove all
+  // connections from input/uses first before removing any instruction.
+  // This method assumes the instructions have been removed from all users with the exception of
+  // catch phis because of missing exceptional edges in the graph.
+  void RemoveCatchPhiUsesAndInstruction(bool building_dominator_tree);
 
   void AddInstruction(HInstruction* instruction);
   // Insert `instruction` before/after an existing instruction `cursor`.