Revert "Revert "Null check elimination improvement""
This reverts commit 31aa97cfec5ee76b2f2496464e1b6f9e11d21a29.
..and thereby brings back change 380165, which was reverted
because it was buggy.
Three problems with the original CL:
1. The author ran the pre-submit tests, but used -j24 and
failed to search the output for fail messages.
2. The new null check analysis pass uses an interative
approach to identify whether a null check is needed. It
is possible that the null-check-required state may
oscillate, and a logic error caused it to stick in the
"no check needed" state.
3. Our old nemesis Dalvik untyped constants, in which 0 values
can be used both as object reference and non-object references.
This CL conservatively treats all CONST definitions as
potential object definitions for the purposes of null
check elimination.
Change-Id: I3c1744e44318276e42989502a314585e56ac57a0
5 files changed
