Subzero: Add rudimentary statistics on generated code.

Subzero: Add rudimentary statistics on generated code.

The following are collected:
- Number of machine instructions emitted
- Number of registers saved/restored in prolog/epilog
- Number of stack frame bytes (non-alloca) allocated
- Number of "spills", or stores to stack slots
- Number of "fills", or loads/operations from stack slots
- Fill+Spill count (sum of above two)

These are somewhat reasonable approximations of code quality, and the primary intention is to compare before-and-after when trying out an optimization.

The statistics are dumped after translating each function.  Per-function and cumulative statistics are collected.  The output lines have a prefix that is easy to filter.

BUG= none
R=jvoung@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=1873560a5b49434905d52460532c7fcce9b7e6de

[Jim Stichnoth, 2014-09-16 23:58:13]

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

[jvoung (off chromium), 2014-09-17 01:21:12]

LGTM

https://codereview.chromium.org/580633002/diff/1/src/IceCfgNode.cpp
File src/IceCfgNode.cpp (right):

https://codereview.chromium.org/580633002/diff/1/src/IceCfgNode.cpp#newcode488
src/IceCfgNode.cpp:488: if (uint32_t Count = (*I)->getEmitInstCount()) {
At some point we'll have to have a convention for omitting code from Release
builds.

https://codereview.chromium.org/580633002/diff/1/src/IceGlobalContext.h
File src/IceGlobalContext.h (right):

https://codereview.chromium.org/580633002/diff/1/src/IceGlobalContext.h#newco...
src/IceGlobalContext.h:55: Str << "|" << Name << "|Spills+Fills|" <<
SpillsPlusFills << "\n";
nit: Seems like this could have been Spills + Fills w/out an extra field to
track the total?

[Jim Stichnoth, 2014-09-17 02:57:06]

https://codereview.chromium.org/580633002/diff/1/src/IceGlobalContext.h
File src/IceGlobalContext.h (right):

https://codereview.chromium.org/580633002/diff/1/src/IceGlobalContext.h#newco...
src/IceGlobalContext.h:55: Str << "|" << Name << "|Spills+Fills|" <<
SpillsPlusFills << "\n";
On 2014/09/17 01:21:12, jvoung wrote:
> nit: Seems like this could have been Spills + Fills w/out an extra field to
> track the total?

True!  Done.

[Jim Stichnoth, 2014-09-17 02:59:41]

Committed patchset #2 (id:20001) manually as 1873560 (presubmit successful).