Subzero: Simplify the FakeKill instruction.
Even after earlier simplifications, FakeKill was still handled somewhat inefficiently for the register allocator. For x86-32, any function containing call instructions would result in about 11 pre-colored Variables, each with an identical and relatively complex live range consisting of points. They would start out on the UnhandledPrecolored list, then all move to the Inactive list, where they would be repeatedly compared against each register allocation candidate via overlapsRange().
We improve this by keeping around a single copy of that live range and directly masking out the Free[] register set when that live range overlaps the current candidate's live range. This saves ~10 overlaps() calculations per candidate while FakeKills are still pending.
Also, slightly rearrange the initialization of the Unhandled etc. sets into a separate init routine, which will make it easier to reuse the register allocator in other situations such as Om1 post-lowering.
BUG= none
R=jvoung@chromium.org
Review URL: https://codereview.chromium.org/720343003
10 files changed