Subzero: Improve the use of NodeList objects.

Subzero: Improve the use of NodeList objects.

Currently NodeList is defined as std::vector<CfgNode*>, but in the future it may be desirable to change it to something like std::list<CfgNode*> so that it is easier to split edges and insert the new nodes at the right locations, rather than re-sorting them in a separate pass.

This gets us closer by using foo.front() instead of foo[0].  There are still a couple more places using the [] operator, but the changes would be more intrusive.

Also, a few instances of ".size()==0" are changed to the possibly more efficient ".empty()".

BUG= none
R=jvoung@chromium.org, kschimpf@google.com

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=bfb410dd04d46ca34b2ea437151af2dc26930b5b

[Jim Stichnoth, 2014-11-05 23:14:05]

stichnot@chromium.org changed reviewers:
+ jvoung@chromium.org, kschimpf@google.com

[Karl, 2014-11-05 23:24:38]

https://codereview.chromium.org/704753007/diff/1/src/IceCfg.cpp
File src/IceCfg.cpp (right):

https://codereview.chromium.org/704753007/diff/1/src/IceCfg.cpp#newcode192
src/IceCfg.cpp:192: SizeT OldSize = Nodes.size();
Note: One of the downsides to this is that size is O(N) if it is a list.

https://codereview.chromium.org/704753007/diff/1/src/IceCfg.cpp#newcode193
src/IceCfg.cpp:193: (void)OldSize;
Why is this necessary?

[Jim Stichnoth, 2014-11-05 23:39:46]

https://codereview.chromium.org/704753007/diff/1/src/IceCfg.cpp
File src/IceCfg.cpp (right):

https://codereview.chromium.org/704753007/diff/1/src/IceCfg.cpp#newcode192
src/IceCfg.cpp:192: SizeT OldSize = Nodes.size();
On 2014/11/05 23:24:37, Karl wrote:
> Note: One of the downsides to this is that size is O(N) if it is a list.

In C++11, the complexity is constant.

https://codereview.chromium.org/704753007/diff/1/src/IceCfg.cpp#newcode193
src/IceCfg.cpp:193: (void)OldSize;
On 2014/11/05 23:24:37, Karl wrote:
> Why is this necessary?

OldSize is only used in the assert, so otherwise you get a warning with the
NOASSERT=1 build.

[Karl, 2014-11-05 23:42:07]

lgtm

[jvoung (off chromium), 2014-11-05 23:57:44]

lgtm

[Jim Stichnoth, 2014-11-06 00:04:11]

Committed patchset #1 (id:1) manually as
bfb410dd04d46ca34b2ea437151af2dc26930b5b (presubmit successful).