MIPS: port Remove the fcontext field from all contexts.

Ported 8452 (8a2a360)

Original commit message:
Before: every context cached the nearest enclosing function context. This
assumed that for nested contexts (i.e., with and catch contexts) the
enclosing function had a materialized link in the context chain.
Now: when necessary, we loop up the context chain to find such a context.
This enables catch contexts without forcing the enclosing function to
allocate its own context.

BUG=
TEST=

Review URL: http://codereview.chromium.org/7284025

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8477 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/code-stubs-mips.cc

@@ -166,7 +166,6 @@ void FastNewContextStub::Generate(MacroAssembler* masm) {
   // Setup the fixed slots.
   __ li(a1, Operand(Smi::FromInt(0)));
   __ sw(a3, MemOperand(v0, Context::SlotOffset(Context::CLOSURE_INDEX)));
-  __ sw(v0, MemOperand(v0, Context::SlotOffset(Context::FCONTEXT_INDEX)));
   __ sw(cp, MemOperand(v0, Context::SlotOffset(Context::PREVIOUS_INDEX)));
   __ sw(a1, MemOperand(v0, Context::SlotOffset(Context::EXTENSION_INDEX)));
 

src/mips/full-codegen-mips.cc

@@ -718,10 +718,14 @@ void FullCodeGenerator::EmitDeclaration(Variable* variable,
         // context.
         ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
         if (FLAG_debug_code) {
-          // Check that we're not inside a 'with'.
-          __ lw(a1, ContextOperand(cp, Context::FCONTEXT_INDEX));
-          __ Check(eq, "Unexpected declaration in current context.",
-                   a1, Operand(cp));
+          // Check that we're not inside a with or catch context.
+          __ lw(a1, FieldMemOperand(cp, HeapObject::kMapOffset));
+          __ LoadRoot(t0, Heap::kWithContextMapRootIndex);
+          __ Check(ne, "Declaration in with context.",
+                   a1, Operand(t0));
+          __ LoadRoot(t0, Heap::kCatchContextMapRootIndex);
+          __ Check(ne, "Declaration in catch context.",
+                   a1, Operand(t0));
         }
         if (mode == Variable::CONST) {
           __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
@@ -1879,17 +1883,7 @@ void FullCodeGenerator::EmitVariableAssignment(Variable* var,
         __ Branch(&skip, ne, a1, Operand(t0));
         __ sw(result_register(), MemOperand(fp, SlotOffset(slot)));
         break;
-      case Slot::CONTEXT: {
-        __ lw(a1, ContextOperand(cp, Context::FCONTEXT_INDEX));
-        __ lw(a2, ContextOperand(a1, slot->index()));
-        __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
-        __ Branch(&skip, ne, a2, Operand(t0));
-        __ sw(result_register(), ContextOperand(a1, slot->index()));
-        int offset = Context::SlotOffset(slot->index());
-        __ mov(a3, result_register());  // Preserve the stored value in v0.
-        __ RecordWrite(a1, Operand(offset), a3, a2);
-        break;
-      }
+      case Slot::CONTEXT:
       case Slot::LOOKUP:
         __ push(result_register());
         __ li(a0, Operand(slot->var()->name()));

src/mips/macro-assembler-mips.cc

@@ -3715,17 +3715,6 @@ void MacroAssembler::LoadContext(Register dst, int context_chain_length) {
     // cannot be allowed to destroy the context in esi).
     Move(dst, cp);
   }
-
-  // We should not have found a 'with' context by walking the context chain
-  // (i.e., the static scope chain and runtime context chain do not agree).
-  // A variable occurring in such a scope should have slot type LOOKUP and
-  // not CONTEXT.
-  if (emit_debug_code()) {
-    lw(t9, MemOperand(dst, Context::SlotOffset(Context::FCONTEXT_INDEX)));
-    Check(eq, "Yo dawg, I heard you liked function contexts "
-              "so I put function contexts in all your contexts",
-               dst, Operand(t9));
-  }
 }