Remove isolate pointer from context objects.

runtime/vm/stub_code_x64.cc

Index: runtime/vm/stub_code_x64.cc
===================================================================
--- runtime/vm/stub_code_x64.cc	(revision 41244)
+++ runtime/vm/stub_code_x64.cc	(working copy)
@@ -44,8 +44,7 @@
 
   __ EnterFrame(0);
 
-  // Load current Isolate pointer from Context structure into RAX.
-  __ movq(RAX, FieldAddress(CTX, Context::isolate_offset()));
+  __ LoadIsolate(RAX);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
@@ -156,8 +155,7 @@
 
   __ EnterFrame(0);
 
-  // Load current Isolate pointer from Context structure into R8.
-  __ movq(R8, FieldAddress(CTX, Context::isolate_offset()));
+  __ LoadIsolate(R8);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
@@ -245,8 +243,7 @@
 
   __ EnterFrame(0);
 
-  // Load current Isolate pointer from Context structure into R8.
-  __ movq(R8, FieldAddress(CTX, Context::isolate_offset()));
+  __ LoadIsolate(R8);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
@@ -979,13 +976,6 @@
     // R10: number of context variables as integer value (not object).
     __ movq(FieldAddress(RAX, Context::num_variables_offset()), R10);
 
-    // Setup isolate field.
-    // RAX: new object.
-    // R10: number of context variables.
-    // R13: Isolate, not an object.
-    __ LoadIsolate(R13);
-    __ movq(FieldAddress(RAX, Context::isolate_offset()), R13);
-
     // Setup the parent field.
     // RAX: new object.
     // R10: number of context variables.
@@ -1754,7 +1744,7 @@
 void StubCode::GenerateDebugStepCheckStub(Assembler* assembler) {
   // Check single stepping.
   Label stepping, done_stepping;
-  __ movq(RAX, FieldAddress(CTX, Context::isolate_offset()));
+  __ LoadIsolate(RAX);
   __ movzxb(RAX, Address(RAX, Isolate::single_step_offset()));
   __ cmpq(RAX, Immediate(0));
   __ j(NOT_EQUAL, &stepping, Assembler::kNearJump);
@@ -2021,7 +2011,7 @@
     Assembler* assembler) {
   // Check single stepping.
   Label stepping, done_stepping;
-  __ movq(RAX, FieldAddress(CTX, Context::isolate_offset()));
+  __ LoadIsolate(RAX);
   __ movzxb(RAX, Address(RAX, Isolate::single_step_offset()));
   __ cmpq(RAX, Immediate(0));
   __ j(NOT_EQUAL, &stepping);