tree 7b620a6ae14db367b2585363e7b032d398c6f805
parent c5abdc1301260c79f60d60ec1117e8044312da30
author Jim Stichnoth <stichnot@chromium.org> 1444426406 -0700
committer Jim Stichnoth <stichnot@chromium.org> 1444426406 -0700

Subzero: Implement "second-chance bin-packing" for register allocation.

If a variable gets a register but is later evicted because of a higher-weight variable, there's a chance that the first variable could have been allocated a register if only its initial choice had been different.

To improve this, we keep track of which variables are evicted, and then allow register allocation to run again, focusing only on those once-evicted variables, and not changing any previous register assignments.

This can iterate until there are no more evictions.

This is more or less what the linear-scan literature describes as "second-chance bin-packing".

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4095
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/1395693005 .