Add support to do suspend polling on backward branches in JIT'ed code.

The polling is expensive for now as it is done through three
instructions: ld/ld/branch. As a result, a bunch of bonus stuff has
been worked on to mitigate the extra overhead:

- Cleaned up resource flags for memory disambiguation.
- Rewrote load/store elimination and scheduler routines to hide
  the ld/ld latency for GC flag. Seperate the dependency checking into
  memory disambiguation part and resource conflict part.
- Allowed code motion for Dalvik/constant/non-aliasing loads to be
  hoisted above branches for null/range checks.
- Created extended basic blocks following goto instructions so that
  longer instruction streams can be optimized as a whole.

Without the bonus stuff, the performance dropped about ~5-10% on some
benchmarks because of the lack of headroom to hide the polling latency
in tight loops. With the bonus stuff, the performance delta is between
+/-5% with polling code generated. With the bonus stuff but disabling
polling, the new bonus stuff provides consistent performance
improvements:

CaffeineMark  3.6%
Linpack      11.1%
Scimark       9.7%
Sieve        33.0%
Checkers      6.0%

As a result, GC polling is disabled by default but can be turned on
through the -Xjitsuspendpoll flag for experimental purposes.

Change-Id: Ia81fc85de3e2b70e6cc93bc37c2b845892003cdb

1 files changed, 1 insertions, 0 deletions

diff --git a/vm/compiler/CompilerIR.h b/vm/compiler/CompilerIR.h
index 89cd1414d..271c31be2 100644
--- a/vm/compiler/CompilerIR.h
+++ b/vm/compiler/CompilerIR.h
@@ -251,6 +251,7 @@ typedef struct CompilationUnit {
     BasicBlock *entryBlock;
     BasicBlock *exitBlock;
     BasicBlock *curBlock;
+    BasicBlock *nextCodegenBlock;       // for extended trace codegen
     GrowableList dfsOrder;
     GrowableList domPostOrderTraversal;
     BitVector *tryBlockAddr;