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
diff --git a/compiler/dex/mir_dataflow.cc b/compiler/dex/mir_dataflow.cc
index 9c8ce23..11e19dc 100644
--- a/compiler/dex/mir_dataflow.cc
+++ b/compiler/dex/mir_dataflow.cc
@@ -1243,7 +1243,8 @@
if (mir->ssa_rep == NULL) {
continue;
}
- uint32_t weight = std::min(16U, static_cast<uint32_t>(bb->nesting_depth));
+ // Each level of nesting adds *16 to count, up to 3 levels deep.
+ uint32_t weight = std::min(3U, static_cast<uint32_t>(bb->nesting_depth) * 4);
for (int i = 0; i < mir->ssa_rep->num_uses; i++) {
int s_reg = mir->ssa_rep->uses[i];
raw_use_counts_.Increment(s_reg);