Skip null check in MarkGCCard() for known non-null values.

Use GVN's knowledge of non-null values to set a new MIR flag
for IPUT/SPUT/APUT to skip the value null check.

Change-Id: I97a8d1447acb530c9bbbf7b362add366d1486ee1
diff --git a/compiler/dex/compiler_enums.h b/compiler/dex/compiler_enums.h
index b56fd6f..4d377df 100644
--- a/compiler/dex/compiler_enums.h
+++ b/compiler/dex/compiler_enums.h
@@ -316,9 +316,8 @@
 
 enum MIROptimizationFlagPositions {
   kMIRIgnoreNullCheck = 0,
-  kMIRNullCheckOnly,
   kMIRIgnoreRangeCheck,
-  kMIRRangeCheckOnly,
+  kMIRStoreNonNullValue,              // Storing non-null value, always mark GC card.
   kMIRClassIsInitialized,
   kMIRClassIsInDexCache,
   kMirIgnoreDivZeroCheck,