Optimize functions needing a local context....

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
===================================================================
--- src/ia32/lithium-codegen-ia32.cc	(revision 6838)
+++ src/ia32/lithium-codegen-ia32.cc	(working copy)
@@ -137,6 +137,46 @@
   __ 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) {