Refactor HGraphBuilder and SsaBuilder to remove HLocals

This patch merges the instruction-building phases from HGraphBuilder
and SsaBuilder into a single HInstructionBuilder class. As a result,
it is not necessary to generate HLocal, HLoadLocal and HStoreLocal
instructions any more, as the builder produces SSA form directly.

Saves 5-15% of arena-allocated memory (see bug for more data):
  GMS      20.46MB  =>  19.26MB  (-5.86%)
  Maps     24.12MB  =>  21.47MB  (-10.98%)
  YouTube  28.60MB  =>  26.01MB  (-9.05%)

Bug: 27894376
Change-Id: Iefe28d40600c169c5d306fd2c77034ae19476d90

1 files changed, 4 insertions, 13 deletions

diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 9f448af73a..1086cbf503 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -318,21 +318,11 @@ void HGraph::SimplifyLoop(HBasicBlock* header) {
     }
   }
 
-  // Place the suspend check at the beginning of the header, so that live registers
-  // will be known when allocating registers. Note that code generation can still
-  // generate the suspend check at the back edge, but needs to be careful with
-  // loop phi spill slots (which are not written to at back edge).
   HInstruction* first_instruction = header->GetFirstInstruction();
-  if (first_instruction == nullptr) {
-    HSuspendCheck* check = new (arena_) HSuspendCheck(header->GetDexPc());
-    header->AddInstruction(check);
-    first_instruction = check;
-  } else if (!first_instruction->IsSuspendCheck()) {
-    HSuspendCheck* check = new (arena_) HSuspendCheck(header->GetDexPc());
-    header->InsertInstructionBefore(check, first_instruction);
-    first_instruction = check;
+  if (first_instruction != nullptr && first_instruction->IsSuspendCheck()) {
+    // Called from DeadBlockElimination. Update SuspendCheck pointer.
+    info->SetSuspendCheck(first_instruction->AsSuspendCheck());
   }
-  info->SetSuspendCheck(first_instruction->AsSuspendCheck());
 }
 
 void HGraph::ComputeTryBlockInformation() {
@@ -1882,6 +1872,7 @@ HInstruction* HGraph::InlineInto(HGraph* outer_graph, HInvoke* invoke) {
            instr_it.Advance()) {
         HInstruction* current = instr_it.Current();
         if (current->NeedsEnvironment()) {
+          DCHECK(current->HasEnvironment());
           current->GetEnvironment()->SetAndCopyParentChain(
               outer_graph->GetArena(), invoke->GetEnvironment());
         }