This optimization is the dual to load elimination. It uses
the same infrastructure for handling aliasing. Since dead
store elimination is a backward data-flow analysis it inherits
from LivenessAnalysis.
Instead of eliminating upward exposed loads, it eliminates
downward exposed stores.
First local intra-block analysis is done in ComputeInitialSets.
Afte the fixed point iteration EliminateDeadStores performs the
global optimization on downward exposed stores in each block.
Only fully dead stores are eliminated. No partially dead
stores yet.
Example:
1: o.x = null;
2: if (cond) {
3: o.x = 1;
4: } else {
5: o.x = 2;
6: }
The store in line 1 is fully dead and will be removed. Note that
any deoptimization in "cond" will make the store only partially
dead and it won't be removed yet.
R=vegorov@google.com
Review URL: https://codereview.chromium.org//143263010
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@35909 260f80e4-7a28-3924-810f-c04153c831b5
fschneider@google.com
16e03db724