Optimize functions needing a local context....

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 119 matching lines @@
       info_->function()->name()->IsEqualTo(CStrVector(FLAG_stop_at))) {
     __ int3();
   }
 #endif
 
   __ push(ebp);  // Caller's frame pointer.
   __ mov(ebp, esp);
   __ push(esi);  // Callee's context.
   __ push(edi);  // Callee's JS function.
 
+  // Possibly allocate a local context.
+  int heap_slots = scope()->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;

[Vyacheslav Egorov (Chromium), 2011/02/18 10:23:49]

Drive by question: this code is basically shared with full-codegen (except for
safepoint).

Can we avoid code duplication?

[rossberg, 2011/02/21 16:40:42]

According to Kevin, there unfortunately is no good place to put this code such
that it can be shared. Nor is there a nice way to factor out the (minor)
differences.

+  if (heap_slots > 0) {
+    Comment(";;; Allocate local context");
+    // Argument to NewContext is the function, which is still in edi.
+    __ push(edi);
+    if (heap_slots <= FastNewContextStub::kMaximumSlots) {
+      FastNewContextStub stub(heap_slots);
+      __ CallStub(&stub);

[Mads Ager (chromium), 2011/02/17 15:49:07]

Is there a reason for not using CallCode here which would deal with the
safepoint?

[rossberg, 2011/02/21 16:40:42]

Yes: that function needs an explicit LInstruction, which we don't have here.

+    } else {
+      __ CallRuntime(Runtime::kNewContext, 1);

[Mads Ager (chromium), 2011/02/17 15:49:07]

Ditto, is there a reason for not using CallRuntime here which would deal with
the safepoint?

[rossberg, 2011/02/21 16:40:42]

Same here.

+    }
+    safepoints_.DefineSafepoint(masm(), Safepoint::kSimple, 0,

[Mads Ager (chromium), 2011/02/17 15:49:07]

If you cannot use the function above, could you use the RecordSafepoint function
here?

[rossberg, 2011/02/21 16:40:42]

Same problem, we'd need an LPointerMap to use that function.

+                                Safepoint::kNoDeoptimizationIndex);
+    // Context is returned in both eax and esi.  It replaces the context
+    // passed to us.  It's saved in the stack and kept live in esi.
+    __ mov(Operand(ebp, StandardFrameConstants::kContextOffset), esi);
+
+    // Copy parameters into context if necessary.
+    int num_parameters = scope()->num_parameters();
+    for (int i = 0; i < num_parameters; i++) {
+      Slot* slot = scope()->parameter(i)->AsSlot();
+      if (slot != NULL && slot->type() == Slot::CONTEXT) {
+        int parameter_offset = StandardFrameConstants::kCallerSPOffset +
+            (num_parameters - 1 - i) * kPointerSize;
+        // Load parameter from stack.
+        __ mov(eax, Operand(ebp, parameter_offset));
+        // Store it in the context.
+        int context_offset = Context::SlotOffset(slot->index());
+        __ mov(Operand(esi, context_offset), eax);
+        // Update the write barrier. This clobbers all involved
+        // registers, so we have use a third register to avoid

[Mads Ager (chromium), 2011/02/17 15:49:07]

we have use -> we have to use

[rossberg, 2011/02/21 16:40:42]

Done.

+        // clobbering esi.
+        __ mov(ecx, esi);
+        __ RecordWrite(ecx, context_offset, eax, ebx);
+      }
+    }
+    Comment(";;; End allocate local context");
+  }
+
   // Reserve space for the stack slots needed by the code.
   int slots = StackSlotCount();
   if (slots > 0) {
     if (FLAG_debug_code) {
       __ mov(Operand(eax), Immediate(slots));
       Label loop;
       __ bind(&loop);
       __ push(Immediate(kSlotsZapValue));
       __ dec(eax);
       __ j(not_zero, &loop);
@@ skipping 3654 matching lines @@
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32