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/call_arm64.cc b/compiler/dex/quick/arm64/call_arm64.cc
index d319f53..56dcbe5 100644
--- a/compiler/dex/quick/arm64/call_arm64.cc
+++ b/compiler/dex/quick/arm64/call_arm64.cc
@@ -202,7 +202,7 @@
     null_check_branch = nullptr;  // No null check.
   } else {
     // If the null-check fails its handled by the slow-path to reduce exception related meta-data.
-    if (!cu_->compiler_driver->GetCompilerOptions().GetImplicitNullChecks()) {
+    if (cu_->compiler_driver->GetCompilerOptions().GetExplicitNullChecks()) {
       null_check_branch = OpCmpImmBranch(kCondEq, rs_x0, 0, NULL);
     }
   }
@@ -250,7 +250,7 @@
     null_check_branch = nullptr;  // No null check.
   } else {
     // If the null-check fails its handled by the slow-path to reduce exception related meta-data.
-    if (!cu_->compiler_driver->GetCompilerOptions().GetImplicitNullChecks()) {
+    if (cu_->compiler_driver->GetCompilerOptions().GetExplicitNullChecks()) {
       null_check_branch = OpCmpImmBranch(kCondEq, rs_x0, 0, NULL);
     }
   }
@@ -338,7 +338,7 @@
   const int frame_size_without_spills = frame_size_ - spill_size;
 
   if (!skip_overflow_check) {
-    if (!cu_->compiler_driver->GetCompilerOptions().GetImplicitStackOverflowChecks()) {
+    if (cu_->compiler_driver->GetCompilerOptions().GetExplicitStackOverflowChecks()) {
       if (!large_frame) {
         // Load stack limit
         LoadWordDisp(rs_xSELF, Thread::StackEndOffset<8>().Int32Value(), rs_x9);
@@ -371,7 +371,7 @@
   }
 
   if (!skip_overflow_check) {
-    if (!cu_->compiler_driver->GetCompilerOptions().GetImplicitStackOverflowChecks()) {
+    if (cu_->compiler_driver->GetCompilerOptions().GetExplicitStackOverflowChecks()) {
       class StackOverflowSlowPath: public LIRSlowPath {
       public:
         StackOverflowSlowPath(Mir2Lir* m2l, LIR* branch, size_t sp_displace) :