Use structural loop info computed by register allocator to mark loop phis.

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph.h"
@@ skipping 704 matching lines @@
   // If this block is a join we need to add destinations of phi
   // resolution moves to phi's live range so that register allocator will
   // fill them with moves.
   JoinEntryInstr* join = block->AsJoinEntry();
   if (join == NULL) return;
 
   // All uses are recorded at the start position in the block.
   const intptr_t pos = join->start_pos();
 
   ZoneGrowableArray<PhiInstr*>* phis = join->phis();
-  if (phis != NULL) {
-    intptr_t move_idx = 0;
-    for (intptr_t phi_idx = 0; phi_idx < phis->length(); phi_idx++) {
-      PhiInstr* phi = (*phis)[phi_idx];
-      if (phi == NULL) continue;
+  if (phis == NULL) return;
 
-      const intptr_t vreg = phi->ssa_temp_index();
-      ASSERT(vreg != -1);
+  const bool is_loop_header = BlockInfoAt(join->start_pos())->is_loop_header();
 
-      // Expected shape of live range:
-      //
-      //                 B
-      //      phi        [--------
-      //
-      LiveRange* range = GetLiveRange(vreg);
-      range->DefineAt(pos);  // Shorten live range.
+  intptr_t move_idx = 0;
+  for (intptr_t phi_idx = 0; phi_idx < phis->length(); phi_idx++) {
+    PhiInstr* phi = (*phis)[phi_idx];
+    if (phi == NULL) continue;
 
-      if (join->loop_info() != NULL) range->mark_loop_phi();
+    const intptr_t vreg = phi->ssa_temp_index();
+    ASSERT(vreg != -1);
 
-      for (intptr_t pred_idx = 0; pred_idx < phi->InputCount(); pred_idx++) {
-        BlockEntryInstr* pred = block->PredecessorAt(pred_idx);
-        GotoInstr* goto_instr = pred->last_instruction()->AsGoto();
-        ASSERT((goto_instr != NULL) && (goto_instr->HasParallelMove()));
-        MoveOperands* move =
-            goto_instr->parallel_move()->MoveOperandsAt(move_idx);
-        move->set_dest(Location::PrefersRegister());
-        range->AddUse(pos, move->dest_slot());
-      }
+    // Expected shape of live range:
+    //
+    //                 B
+    //      phi        [--------
+    //
+    LiveRange* range = GetLiveRange(vreg);
+    range->DefineAt(pos);  // Shorten live range.
 
-      // All phi resolution moves are connected. Phi's live range is
-      // complete.
-      AssignSafepoints(range);
+    if (is_loop_header) range->mark_loop_phi();
 
-      CompleteRange(range, RegisterKindForResult(phi));
+    for (intptr_t pred_idx = 0; pred_idx < phi->InputCount(); pred_idx++) {
+      BlockEntryInstr* pred = block->PredecessorAt(pred_idx);
+      GotoInstr* goto_instr = pred->last_instruction()->AsGoto();
+      ASSERT((goto_instr != NULL) && (goto_instr->HasParallelMove()));
+      MoveOperands* move =
+          goto_instr->parallel_move()->MoveOperandsAt(move_idx);
+      move->set_dest(Location::PrefersRegister());
+      range->AddUse(pos, move->dest_slot());
+    }
 
-      move_idx++;
-    }
+    // All phi resolution moves are connected. Phi's live range is
+    // complete.
+    AssignSafepoints(range);
+
+    CompleteRange(range, RegisterKindForResult(phi));
+
+    move_idx++;
   }
 }
 
 
 void FlowGraphAllocator::ProcessEnvironmentUses(BlockEntryInstr* block,
                                                 Instruction* current) {
   ASSERT(current->env() != NULL);
   Environment* env = current->env();
   while (env != NULL) {
     // Any value mentioned in the deoptimization environment should survive
@@ skipping 1574 matching lines @@
     OS::Print("-- [after ssa allocator] ir [%s] -------------\n",
               function.ToFullyQualifiedCString());
     FlowGraphPrinter printer(flow_graph_, true);
     printer.PrintBlocks();
     OS::Print("----------------------------------------------\n");
   }
 }
 
 
 }  // namespace dart