Implement deoptimization in the SSA compiler as a parallel move.

runtime/vm/flow_graph_compiler_x64.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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "lib/error.h"
@@ skipping 19 matching lines @@
   __ Comment("Deopt stub for id %d", deopt_id_);
   __ Bind(entry_label());
 
   if (deoptimization_env_ == NULL) {
     for (intptr_t i = 0; i < registers_.length(); i++) {
       if (registers_[i] != kNoRegister) {
         __ pushq(registers_[i]);
       }
     }
   } else {
-    // We have a deoptimization environment, we have to tear down optimized
-    // frame and recreate non-optimized one.
-    __ leaq(RSP,
-            Address(RBP, ParsedFunction::kFirstLocalSlotIndex * kWordSize));
+    // We have a deoptimization environment, we have to tear down the
+    // optimized frame and recreate a non-optimized one.
 
+    // 1. Set the stack pointer to the top of the non-optimized frame.
     const GrowableArray<Value*>& values = deoptimization_env_->values();
+    const int top_offset =
+        ParsedFunction::kFirstLocalSlotIndex - values.length();

[Vyacheslav Egorov (Google), 2012/07/26 12:59:56]

this should have been actually ParsedFunction::kFirstLocalSlotIndex -
(values.length() - 1)

Because if we have one local we should do Address(EBP, -2 * kWordSize) to get to
it. 

(yep it was incorrect initially as well).

+    __ leaq(RSP, Address(RBP, top_offset * kWordSize));
+
+    // 2. Build and emit a parallel move representing the frame translation.
+    ParallelMoveInstr* move = new ParallelMoveInstr();
     for (intptr_t i = 0; i < values.length(); i++) {
-      const Location loc = deoptimization_env_->LocationAt(i);
-      if (loc.IsInvalid()) {
-        ASSERT(values[i]->IsConstant());
-        __ PushObject(values[i]->AsConstant()->value());
-      } else if (loc.IsRegister()) {
-        __ pushq(loc.reg());
-      } else {
+      Location destination = Location::SpillSlot(i);
+      Location source = deoptimization_env_->LocationAt(i);
+      if (!source.IsRegister() && !source.IsInvalid()) {
         compiler->Bailout("unsupported deoptimization state");
       }
+      if (source.IsInvalid()) {
+        ASSERT(values[i]->IsConstant());
+        source = Location::Constant(values[i]->AsConstant()->value());
+      }
+      move->AddMove(destination, source);
     }
+    compiler->parallel_move_resolver()->EmitNativeCode(move);
   }
 
   if (compiler->IsLeaf()) {
     Label L;
     __ call(&L);
     const intptr_t offset = assem->CodeSize();
     __ Bind(&L);
     __ popq(RAX);
     __ subq(RAX,
         Immediate(offset - AssemblerMacros::kOffsetOfSavedPCfromEntrypoint));
@@ skipping 1140 matching lines @@
 void ParallelMoveResolver::Exchange(const Address& mem1, const Address& mem2) {
   __ Exchange(mem1, mem2);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64