Add enough compiler support to compile empty functions on x64.

Add enough compiler support to compile empty functions on x64.

Implement a simple compilation visitor for the intermediate language.  Copy
code from the x64 code generator to support compilation of functions with no
arguments, no locals, and that return a literal.

Compiled code is not used, but it can be disassembled and visually checked
against the code from the old code generator.

R=srdjan@google.com
BUG=
TEST=expected to pass all tests on x64

Committed: https://code.google.com/p/dart/source/detail?r=4601

[Kevin Millikin (Google), 2012-02-24 14:40:44]

I'm aware that this is *extremely* rough.  Think of it as a way to get the basic
infrastructure in place.

Obviously, copying and pasting from the existing code generator can not be a
long-term solution.

[Kevin Millikin (Google), 2012-02-24 14:42:22]

Also: it includes the changes from http://codereview.chromium.org/9463007/ which
I will land first or revert from this change as we decide.

[srdjan, 2012-02-24 23:13:01]

LGTM with comments

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/code_genera...
File runtime/vm/code_generator_x64.h (right):

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/code_genera...
runtime/vm/code_generator_x64.h:87: class DescriptorList;
Why the move?

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/code_genera...
runtime/vm/code_generator_x64.h:233: class CodeGenerator::DescriptorList :
public ZoneAllocated {
Remove since I have moved it into code_generator.h

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/compiler.cc
File runtime/vm/compiler.cc (right):

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/compiler.cc...
runtime/vm/compiler.cc:126: if (FLAG_use_new_compiler) {
ASSERT(!optimized).

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/compiler.cc...
runtime/vm/compiler.cc:140: graph_compiler.CompileGraph();
It would be better to implement "dummy" FlowGraphCompiler in _ia32 and simarm.
This can happen in a later CL (please add a TODO).

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/flow_graph_...
File runtime/vm/flow_graph_compiler_x64.h (right):

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/flow_graph_...
runtime/vm/flow_graph_compiler_x64.h:22: explicit FlowGraphCompiler(Assembler*
assembler,
remove explicit

https://chromiumcodereview.appspot.com/9464009/diff/11/runtime/vm/flow_graph_...
runtime/vm/flow_graph_compiler_x64.h:44: // Compile a Value into register RAX.
Why into RAX and not on TOS?

[Kevin Millikin (Google), 2012-02-27 08:22:06]

http://codereview.chromium.org/9464009/diff/11/runtime/vm/code_generator_x64.h
File runtime/vm/code_generator_x64.h (right):

http://codereview.chromium.org/9464009/diff/11/runtime/vm/code_generator_x64....
runtime/vm/code_generator_x64.h:87: class DescriptorList;
On 2012/02/24 23:13:02, srdjan wrote:
> Why the move?

Making it public for class FlowGraphCompiler.  A friend class seemed
unnecessary.

http://codereview.chromium.org/9464009/diff/11/runtime/vm/code_generator_x64....
runtime/vm/code_generator_x64.h:233: class CodeGenerator::DescriptorList :
public ZoneAllocated {
On 2012/02/24 23:13:02, srdjan wrote:
> Remove since I have moved it into code_generator.h

Thanks, done.

http://codereview.chromium.org/9464009/diff/11/runtime/vm/compiler.cc
File runtime/vm/compiler.cc (right):

http://codereview.chromium.org/9464009/diff/11/runtime/vm/compiler.cc#newcode126
runtime/vm/compiler.cc:126: if (FLAG_use_new_compiler) {
On 2012/02/24 23:13:02, srdjan wrote:
> ASSERT(!optimized).

Done.

http://codereview.chromium.org/9464009/diff/11/runtime/vm/compiler.cc#newcode140
runtime/vm/compiler.cc:140: graph_compiler.CompileGraph();
On 2012/02/24 23:13:02, srdjan wrote:
> It would be better to implement "dummy" FlowGraphCompiler in _ia32 and simarm.
> This can happen in a later CL (please add a TODO).

Agreed.  Done.

http://codereview.chromium.org/9464009/diff/11/runtime/vm/flow_graph_compiler...
File runtime/vm/flow_graph_compiler_x64.h (right):

http://codereview.chromium.org/9464009/diff/11/runtime/vm/flow_graph_compiler...
runtime/vm/flow_graph_compiler_x64.h:22: explicit FlowGraphCompiler(Assembler*
assembler,
On 2012/02/24 23:13:02, srdjan wrote:
> remove explicit

Thanks, done.

http://codereview.chromium.org/9464009/diff/11/runtime/vm/flow_graph_compiler...
runtime/vm/flow_graph_compiler_x64.h:44: // Compile a Value into register RAX.
On 2012/02/24 23:13:02, srdjan wrote:
> Why into RAX and not on TOS?

This is 'pop', when we consume a value (for temps they should already be on top
of the stack).

I'll rename it LoadValue.  Eventually we'll want an explicit register argument,
I think, but I'll wait until that's obvious.