Fix self-verification to handle loop traces with single-step instructions.
(cherry-picked from dalvik-dev)
Change-Id: If1414d0e6767d36e33db8837e52dc91d11b4969b
diff --git a/vm/interp/Jit.c b/vm/interp/Jit.c
index 4129e8a..fda9f18 100644
--- a/vm/interp/Jit.c
+++ b/vm/interp/Jit.c
@@ -173,6 +173,28 @@
// Special case when punting after a single instruction
if (exitState == kSVSPunt && pc == shadowSpace->startPC) {
shadowSpace->selfVerificationState = kSVSIdle;
+ } else if (exitState == kSVSBackwardBranch && pc != shadowSpace->startPC) {
+ /*
+ * Consider a loop which contains the following instructions:
+ * 1: ..
+ * 2: ..
+ * 3: ..(single-stepped)
+ * 4: ..
+ * 5: Goto 1
+ *
+ * The state comparisons are conducted in two batches: 1,2 as the
+ * first batch and 4,5 as the second batch. If the execution in the
+ * JIT'ed code is resumed from 4, the start PC for self-verification
+ * will be set to 4. The exit point for 5 is a backward branch and
+ * will suggest the end PC to be 1, and will do the state comparison
+ * when 1 is hit for the second time in the interpreter. It is incorrect
+ * in this case as the work for 1,2 from the current iteration have been
+ * committed and the state comparison has been conducted.
+ *
+ * So we alter the state from BackwardBranch to Normal and state
+ * comparison will be issued immediate following the goto.
+ */
+ shadowSpace->selfVerificationState = kSVSNormal;
} else {
shadowSpace->selfVerificationState = exitState;
}
