Revert "Revert "Revert "Add implicit null and stack checks for x86"""

Broke the build.

This reverts commit 7fb36ded9cd5b1d254b63b3091f35c1e6471b90e.

Change-Id: I9df0e7446ff0913a0e1276a558b2ccf6c8f4c949
diff --git a/compiler/dex/quick/arm64/target_arm64.cc b/compiler/dex/quick/arm64/target_arm64.cc
index 949295d..ef9dbdd 100644
--- a/compiler/dex/quick/arm64/target_arm64.cc
+++ b/compiler/dex/quick/arm64/target_arm64.cc
@@ -1190,7 +1190,7 @@
   call_state = next_call_insn(cu_, info, call_state, target_method, vtable_idx,
                            direct_code, direct_method, type);
   if (pcrLabel) {
-    if (!cu_->compiler_driver->GetCompilerOptions().GetImplicitNullChecks()) {
+    if (cu_->compiler_driver->GetCompilerOptions().GetExplicitNullChecks()) {
       *pcrLabel = GenExplicitNullCheck(TargetReg(kArg1), info->opt_flags);
     } else {
       *pcrLabel = nullptr;