VM: Fix more places with isolate embedded into unoptimized code.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index ec0bbc7602be704c3684b4f7aa88580c51a95693..7aaf5619acb2dc9f6031c27ad75dd4513e2502ba 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -2638,9 +2638,14 @@ void CheckStackOverflowInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 
   Register temp = locs()->temp(0).reg();
   // Generate stack overflow check.
-  __ LoadImmediate(
-      temp, Immediate(Isolate::Current()->stack_limit_address()), PP);
-  __ cmpq(RSP, Address(temp, 0));
+  if (compiler->is_optimizing()) {
+    __ LoadImmediate(
+        temp, Immediate(Isolate::Current()->stack_limit_address()), PP);
+    __ cmpq(RSP, Address(temp, 0));
+  } else {
+    __ LoadIsolate(temp);
+    __ cmpq(RSP, Address(temp, Isolate::stack_limit_offset()));
+  }
   __ j(BELOW_EQUAL, slow_path->entry_label());
   if (compiler->CanOSRFunction() && in_loop()) {
     // In unoptimized code check the usage counter to trigger OSR at loop