Refactor Instruction classes to use a template base class.

vm/intermediate_language_ia32.cc

Index: vm/intermediate_language_ia32.cc
===================================================================
--- vm/intermediate_language_ia32.cc	(revision 10287)
+++ vm/intermediate_language_ia32.cc	(working copy)
@@ -1023,14 +1023,19 @@
 
 
 LocationSummary* CreateArrayComp::MakeLocationSummary() const {
-  return MakeCallSummary();
+  const intptr_t kNumInputs = 1;

[Kevin Millikin (Google), 2012/08/07 10:06:03]

I have a feeling that this is always InputCount() for all
instructions/computations.  I think it would be clearer to write:

new LocationSummary(InputCount(), kNumTemps, LocationSummary::kCall);

Let's consider that for a future change.

[Florian Schneider, 2012/08/07 10:23:55]

Yes, that will be the case once all call-instructions report the correct input
count via InputCount(). There are few instructions left, that don't right now,
but I'll fix those in my next couple of CLs.

+  const intptr_t kNumTemps = 0;
+  LocationSummary* locs =
+      new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kCall);
+  locs->set_in(0, Location::RegisterLocation(ECX));

[Kevin Millikin (Google), 2012/08/07 10:06:03]

I don't really like the number '0' here.  It has to agree in a bunch of places
(the initializer in the constructor, the get accessor, here, and in the codegen
when it's used).  It might be easier to have a "layout" enum describing the
inputs:

enum Layout {
  kElementType,
};

...

locs->set_in(kElementType, Location::RegisterLocation(ECX));

========

Another option is to make Value into a pair of the SSA value and the location
and Definition contain the output location, rather than splitting
(non-temporary) locations out into a separate location summary.  I suppose we
still need a platform-specific list of indexed temporary locations, but
otherwise it seems cleaner.

In class Value:

Location& location() { return location_; }

In class CreateArrayComp:

Value* element_type() const { return inputs_[0]; }

...

// and here:

element_type().location() = Location::RegisterLocation(ECX);

[Florian Schneider, 2012/08/07 10:23:55]

Agreed. Let's consider removing those 0s and 1s in a future CL.

+  locs->set_out(Location::RegisterLocation(EAX));
+  return locs;
 }
 
 
 void CreateArrayComp::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // TODO(fschneider): Support call-instructions that take inputs in registers.
   // Allocate the array.  EDX = length, ECX = element type.
-  __ popl(ECX);
+  ASSERT(locs()->in(0).reg() == ECX);

[Kevin Millikin (Google), 2012/08/07 10:06:03]

There's the 0 again.

   __ movl(EDX,  Immediate(Smi::RawValue(ElementCount())));
   compiler->GenerateCall(token_pos(),
                          try_index(),