Subzero: Implement InstList in terms of llvm::ilist<> .

Subzero: Implement InstList in terms of llvm::ilist<> .

Use LLVM's intrusive list ADT template to implement instruction lists.  This embeds prev/next pointers into the instruction, and as such, iterators essentially double as instruction pointers.  This means stripping off one level of indirection when dereferencing, and also the range-based for loop can't be used.

The performance difference in translation time seems to be 1-2%.

I tried to also do this for the much less used PhiList and AssignList, but ran into SFINAE problems.

BUG= none
R=jvoung@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=607e9f0e947305da9b54df6573920299c9f6610e

[Jim Stichnoth, 2014-11-06 19:46:35]

stichnot@chromium.org changed reviewers:
+ jvoung@chromium.org

[jvoung (off chromium), 2014-11-06 21:20:53]

otherwise LGTM

https://codereview.chromium.org/709533002/diff/1/src/IceInst.h
File src/IceInst.h (right):

https://codereview.chromium.org/709533002/diff/1/src/IceInst.h#newcode841
src/IceInst.h:841: template <>
Can you leave a comment about why the default traits aren't appropriate?

It seems to me that it's because you don't want the "delete".

[Jim Stichnoth, 2014-11-06 21:31:58]

https://codereview.chromium.org/709533002/diff/1/src/IceInst.h
File src/IceInst.h (right):

https://codereview.chromium.org/709533002/diff/1/src/IceInst.h#newcode841
src/IceInst.h:841: template <>
On 2014/11/06 21:20:53, jvoung wrote:
> Can you leave a comment about why the default traits aren't appropriate?
> 
> It seems to me that it's because you don't want the "delete".

Done.  (It's also the private ctor that needs to be avoided.)

Also, I realized that deleteNode() could be combined with the rest of the struct
specialization.

[Jim Stichnoth, 2014-11-06 21:32:08]

Committed patchset #2 (id:20001) manually as
607e9f0e947305da9b54df6573920299c9f6610e (presubmit successful).