Add support for fixed parameters in the register allocator.

runtime/vm/flow_graph_compiler_ia32.cc

Index: runtime/vm/flow_graph_compiler_ia32.cc
diff --git a/runtime/vm/flow_graph_compiler_ia32.cc b/runtime/vm/flow_graph_compiler_ia32.cc
index 15761b3c4210d39e308eeac76e768f2e171a7ff1..748b3bf57e0a920396dab420392e9fcd6f8f68d6 100644
--- a/runtime/vm/flow_graph_compiler_ia32.cc
+++ b/runtime/vm/flow_graph_compiler_ia32.cc
@@ -958,15 +958,24 @@ void FlowGraphCompiler::CompileGraph() {
   } else {
     CopyParameters();
   }
+
+  // TODO(vegorov): introduce stack maps and stop initializing all spill slots
+  // with null.
+  const int stack_slot_count =

[srdjan, 2012/07/26 00:33:56]

s/int/intptr_t/

[Vyacheslav Egorov (Google), 2012/07/26 11:33:53]

Done.

+      is_ssa_ ? block_order_[0]->AsGraphEntry()->spill_slot_count()
+              : local_count;
+
+  const int slot_base =

[srdjan, 2012/07/26 00:33:56]

ditto

[Vyacheslav Egorov (Google), 2012/07/26 11:33:53]

Done.

+      is_ssa_ ? -2 : parsed_function().first_stack_local_index();

[srdjan, 2012/07/26 00:33:56]

Why is this needed? parsed_function().first_stack_local_index() returns -2
except for natives -- which we can leave unoptimized -- and methods with
optional parameters -- which we do not compile anyway. Magic number -2 is also
strange.

[Vyacheslav Egorov (Google), 2012/07/26 11:33:53]

Removed.

+
   // Initialize (non-argument) stack allocated locals to null.
-  if (local_count > 0) {
+  if (stack_slot_count > 0) {
     const Immediate raw_null =
         Immediate(reinterpret_cast<intptr_t>(Object::null()));
     __ movl(EAX, raw_null);
-    const int base = parsed_function().first_stack_local_index();
-    for (int i = 0; i < local_count; ++i) {
+    for (int i = 0; i < stack_slot_count; ++i) {
       // Subtract index i (locals lie at lower addresses than EBP).
-      __ movl(Address(EBP, (base - i) * kWordSize), EAX);
+      __ movl(Address(EBP, (slot_base - i) * kWordSize), EAX);
     }
   }
 
@@ -1110,11 +1119,17 @@ void FlowGraphCompiler::LoadDoubleOrSmiToXmm(XmmRegister result,
 #define __ compiler_->assembler()->
 
 
-static Address ToSpillAddress(Location loc) {
-  ASSERT(loc.IsSpillSlot());
-  const intptr_t offset =
-      (ParsedFunction::kFirstLocalSlotIndex - loc.spill_index()) * kWordSize;
-  return Address(EBP, offset);
+static Address ToStackSlotAddress(Location loc) {
+  ASSERT(loc.IsStackSlot());
+  const intptr_t index = loc.stack_index();
+  if (index < 0) {
+    const intptr_t offset = (1 - index)  * kWordSize;
+    return Address(EBP, offset);
+  } else {
+    const intptr_t offset =
+        (ParsedFunction::kFirstLocalSlotIndex - index) * kWordSize;
+    return Address(EBP, offset);
+  }
 }
 
 
@@ -1127,23 +1142,24 @@ void ParallelMoveResolver::EmitMove(int index) {
     if (destination.IsRegister()) {
       __ movl(destination.reg(), source.reg());
     } else {
-      ASSERT(destination.IsSpillSlot());
-      __ movl(ToSpillAddress(destination), source.reg());
+      ASSERT(destination.IsStackSlot());
+      __ movl(ToStackSlotAddress(destination), source.reg());
     }
-  } else if (source.IsSpillSlot()) {
+  } else if (source.IsStackSlot()) {
     if (destination.IsRegister()) {
-      __ movl(destination.reg(), ToSpillAddress(source));
+      __ movl(destination.reg(), ToStackSlotAddress(source));
     } else {
-      ASSERT(destination.IsSpillSlot());
-      MoveMemoryToMemory(ToSpillAddress(destination), ToSpillAddress(source));
+      ASSERT(destination.IsStackSlot());
+      MoveMemoryToMemory(ToStackSlotAddress(destination),
+                         ToStackSlotAddress(source));
     }
   } else {
     ASSERT(source.IsConstant());
     if (destination.IsRegister()) {
       __ LoadObject(destination.reg(), source.constant());
     } else {
-      ASSERT(destination.IsSpillSlot());
-      StoreObject(ToSpillAddress(destination), source.constant());
+      ASSERT(destination.IsStackSlot());
+      StoreObject(ToStackSlotAddress(destination), source.constant());
     }
   }
 
@@ -1158,12 +1174,12 @@ void ParallelMoveResolver::EmitSwap(int index) {
 
   if (source.IsRegister() && destination.IsRegister()) {
     __ xchgl(destination.reg(), source.reg());
-  } else if (source.IsRegister() && destination.IsSpillSlot()) {
-    Exchange(source.reg(), ToSpillAddress(destination));
-  } else if (source.IsSpillSlot() && destination.IsRegister()) {
-    Exchange(destination.reg(), ToSpillAddress(source));
-  } else if (source.IsSpillSlot() && destination.IsSpillSlot()) {
-    Exchange(ToSpillAddress(destination), ToSpillAddress(source));
+  } else if (source.IsRegister() && destination.IsStackSlot()) {
+    Exchange(source.reg(), ToStackSlotAddress(destination));
+  } else if (source.IsStackSlot() && destination.IsRegister()) {
+    Exchange(destination.reg(), ToStackSlotAddress(source));
+  } else if (source.IsStackSlot() && destination.IsStackSlot()) {
+    Exchange(ToStackSlotAddress(destination), ToStackSlotAddress(source));
   } else {
     UNREACHABLE();
   }