For 64-bit, use 32-bit DEXPREOPT if zygote64 isn't enabled.

Change-Id: Ia95d74517f8182031d6044ae55559010a98ec5ca
diff --git a/core/config.mk b/core/config.mk
index 653a9bc..4e65049 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -493,9 +493,24 @@
   TARGET_DEFAULT_JAVA_LIBRARIES := core core-junit ext framework framework2
 endif
 
+# Flags for DEX2OAT
+DEX2OAT_TARGET_ARCH := $(TARGET_ARCH)
+DEX2OAT_TARGET_CPU_VARIANT := $(TARGET_CPU_VARIANT)
 DEX2OAT_TARGET_INSTRUCTION_SET_FEATURES := default
-ifneq (,$(filter $(TARGET_CPU_VARIANT),cortex-a7 cortex-a15 krait))
-DEX2OAT_TARGET_INSTRUCTION_SET_FEATURES := div
+
+# If for a 64bit build we have a 2nd architecture but the zygote isn't 64bit,
+# assume DEX2OAT should DEXPREOPT for the 2nd architecture.
+ifdef TARGET_2ND_ARCH
+  ifeq (true,$(TARGET_IS_64_BIT))
+    ifeq ($(filter ro.zygote=zygote64,$(PRODUCT_DEFAULT_PROPERTY_OVERRIDES)),)
+      DEX2OAT_TARGET_ARCH := $(TARGET_2ND_ARCH)
+      DEX2OAT_TARGET_CPU_VARIANT := $(TARGET_2ND_CPU_VARIANT)
+    endif
+  endif
+endif
+
+ifneq (,$(filter $(DEX2OAT_TARGET_CPU_VARIANT),cortex-a7 cortex-a15 krait))
+  DEX2OAT_TARGET_INSTRUCTION_SET_FEATURES := div
 endif
 
 # define clang/llvm tools and global flags