VM: Small generated code size improvements on x64.

VM: Small generated code size improvements on x64.

Addtional cleanup in code_patcher on all platforms.

R=zra@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42700

[Florian Schneider, 2015-01-08 15:05:15]

fschneider@google.com changed reviewers:
+ zra@google.com

[zra, 2015-01-08 15:50:09]

Just to get a rough idea of the % improvement in code-size, have you tried
passing --compiler-stats when running a large program like dart2js?

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/flow_graph_co...
File runtime/vm/flow_graph_compiler_x64.cc (right):

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/flow_graph_co...
runtime/vm/flow_graph_compiler_x64.cc:1252: __ Drop(argument_count, RCX);
A comment here (and below for other situations) about why TMP can't be used
would be useful. Also, it seems like this is a bug-fix. Is there a test that
fails?

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/intermediate_...
File runtime/vm/intermediate_language_x64.cc (right):

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/intermediate_...
runtime/vm/intermediate_language_x64.cc:1282: locs->set_in(2,
Location::RequiresRegister());
Merge with Int64 case?

[Florian Schneider, 2015-01-08 16:15:31]

No, I have not run --compiler-stats. It's a few bytes at almost every call, plus
better code for LoadIndexed from Int32-/Uint32Array

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/flow_graph_co...
File runtime/vm/flow_graph_compiler_x64.cc (right):

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/flow_graph_co...
runtime/vm/flow_graph_compiler_x64.cc:1252: __ Drop(argument_count, RCX);
On 2015/01/08 15:50:09, zra wrote:
> A comment here (and below for other situations) about why TMP can't be used
> would be useful. Also, it seems like this is a bug-fix. Is there a test that
> fails?

No bug fix, but TMP requires a REX prefix. Using RCX saves 1 byte.

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/intermediate_...
File runtime/vm/intermediate_language_x64.cc (right):

https://codereview.chromium.org/829133006/diff/40001/runtime/vm/intermediate_...
runtime/vm/intermediate_language_x64.cc:1282: locs->set_in(2,
Location::RequiresRegister());
On 2015/01/08 15:50:09, zra wrote:
> Merge with Int64 case?

Done.

[zra, 2015-01-08 16:23:24]

lgtm

If you have time to grab the numbers it would be interesting to know the extent
of the improvement.

[Florian Schneider, 2015-01-08 16:42:14]

Committed patchset #4 (id:50011) manually as r42700 (presubmit successful).