Subzero: Optimize a common live range overlap calculation.

Subzero: Optimize a common live range overlap calculation.

Call instruction lowering includes the FakeKill instruction, which creates several precolored variables, one for each scratch register.  The live range for each of these variables consists of a set of "point" ranges, one point for every FakeKill instruction.  The overlaps() logic is such that a point range never overlaps with an individual instruction, but it can overlap with a normal non-point range.

It turns out that during register allocation, usually most of the variables on the Inactive list are these FakeKill instructions.  The live range representation can be quite large if there are many calls in the function.  In the "Check for inactive ranges that have expired or reactivated" section, a lot of time was spent on overlapsStart() calls that were doomed to return false.

This change lets the live range keep track of whether it contains non-point segments, and if not, optimize the overlaps(InstNumberT) method.

BUG= none
R=jvoung@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=df861f73ce9f3dff4502be794cfdc23a013427e3

[Jim Stichnoth, 2014-10-04 04:08:35]

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

[Jim Stichnoth, 2014-10-04 04:10:06]

Several of the spec2k components improve translation time by ~20%.

[jvoung (off chromium), 2014-10-04 05:06:34]

Cool! Otherwise LGTM

https://codereview.chromium.org/631483002/diff/1/src/IceOperand.h
File src/IceOperand.h (right):

https://codereview.chromium.org/631483002/diff/1/src/IceOperand.h#newcode305
src/IceOperand.h:305: Weight.setWeight(0);
Seems like reset() should reset IsNonpoints ?

[Jim Stichnoth, 2014-10-04 12:43:51]

Committed patchset #2 (id:20001) manually as
df861f73ce9f3dff4502be794cfdc23a013427e3 (presubmit successful).

[Jim Stichnoth, 2014-10-04 12:44:09]

https://codereview.chromium.org/631483002/diff/1/src/IceOperand.h
File src/IceOperand.h (right):

https://codereview.chromium.org/631483002/diff/1/src/IceOperand.h#newcode305
src/IceOperand.h:305: Weight.setWeight(0);
On 2014/10/04 05:06:34, jvoung wrote:
> Seems like reset() should reset IsNonpoints ?

Done.