Introduce locations based code generation.

runtime/vm/locations.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/locations.h"
+
+#include "vm/intermediate_language.h"
+
+namespace dart {
+
+
+static Register AllocateFreeRegister(
+    EmbeddedArray<bool, kNumberOfCpuRegisters>* blocked_registers) {
+  for (int regno = 0; regno < kNumberOfCpuRegisters; regno++) {

[srdjan, 2012/05/21 16:05:22]

intptr_t

[Vyacheslav Egorov (Google), 2012/05/21 19:53:46]

Done.

+    if (!blocked_registers->At(regno)) {

[Florian Schneider, 2012/05/21 18:33:38]

(*blocked_registers)[regno] should also work here.

[srdjan, 2012/05/21 19:49:43]

I like the idea of getting rid of const overloaded operators and use At and
SetAt, but keeping an open mind :-). Maybe we should agree on using one, and
ditch the other?

[Vyacheslav Egorov (Google), 2012/05/21 19:53:46]

I'll go with a method, it looks nicer.

+      blocked_registers->SetAt(regno, true);

[Florian Schneider, 2012/05/21 18:33:38]

(*blocked_registers)[regno] = true;

should also work here.

[Vyacheslav Egorov (Google), 2012/05/21 19:53:46]

I'll go with a method, it looks nicer.

+      return static_cast<Register>(regno);
+    }
+  }
+  UNREACHABLE();
+  return kNoRegister;
+}
+
+
+void LocationSummary::AllocateRegisters() {
+  EmbeddedArray<bool, kNumberOfCpuRegisters> blocked_registers;
+
+  // Mark all registers free.
+  for (intptr_t i = 0; i < kNumberOfCpuRegisters; i++) {
+    blocked_registers[i] = false;
+  }
+
+  // Mark all fixed registers as used.
+  for (intptr_t i = 0; i < count(); i++) {
+    Location loc = in(i);
+    if (loc.kind() == Location::kRegister) {
+      ASSERT(!blocked_registers[loc.AsRegister()]);
+      blocked_registers[loc.value()] = true;
+    }
+  }
+
+  // Allocate all unallocated input locations.
+  for (intptr_t i = 0; i < count(); i++) {
+    Location loc = in(i);
+    if (loc.kind() == Location::kUnallocated) {
+      ASSERT(UnallocatedLocation::Cast(loc).policy() ==
+             UnallocatedLocation::kRegister);
+      set_in(i, RegisterLocation(
+          AllocateFreeRegister(&blocked_registers)));
+    }
+  }
+
+  Location result_location = out();
+  if (result_location.kind() == Location::kUnallocated) {
+    switch (UnallocatedLocation::Cast(result_location).policy()) {
+      case UnallocatedLocation::kRegister:
+        result_location = RegisterLocation(
+            AllocateFreeRegister(&blocked_registers));
+        break;
+      case UnallocatedLocation::kSameAsFirstInput:
+        result_location = in(0);
+        break;
+    }
+    set_out(result_location);
+  }
+}
+
+
+}  // namespace dart
+