Keep list of uses sorted when building it.

Keep list of uses sorted when building it.

We were violating sorting at instructions that use the same value as both fixed register input and an unallocated one producing a list that contained use at P, followed by a use at P-1.

This would later cause a problem when we split live-range at P-1 and spill [..., P-1) prefix.

Use at P-1 would be attributed to unspilled part of the range leading to completely incorrect parallel move at P-1: [rx <- S+X, ry <- rx], where rx - is the aforementioned fixed register and ry is a register selected for an unallocated use of the value.

R=srdjan@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=40681

[srdjan, 2014-09-25 16:32:44]

lgtm

https://codereview.chromium.org/601103004/diff/1/runtime/vm/flow_graph_alloca...
File runtime/vm/flow_graph_allocator.cc (right):

https://codereview.chromium.org/601103004/diff/1/runtime/vm/flow_graph_alloca...
runtime/vm/flow_graph_allocator.cc:267: UsePosition* LiveRange::AddUse(intptr_t
pos, Location* location_slot) {
Who is using result of LiveRange::AddUse?

[Vyacheslav Egorov (Google), 2014-09-25 17:10:13]

Committed patchset #1 (id:1) manually as 40681 (presubmit successful).