Remove isolate pointer from context objects.

runtime/vm/stub_code_arm64.cc

Index: runtime/vm/stub_code_arm64.cc
===================================================================
--- runtime/vm/stub_code_arm64.cc	(revision 41244)
+++ runtime/vm/stub_code_arm64.cc	(working copy)
@@ -44,8 +44,7 @@
   __ Comment("CallToRuntimeStub");
   __ EnterFrame(0);
 
-  // Load current Isolate pointer from Context structure into R0.
-  __ LoadFieldFromOffset(R0, CTX, Context::isolate_offset(), kNoPP);
+  __ LoadIsolate(R0, kNoPP);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
@@ -161,8 +160,7 @@
 
   __ EnterFrame(0);
 
-  // Load current Isolate pointer from Context structure into R0.
-  __ LoadFieldFromOffset(R0, CTX, Context::isolate_offset(), kNoPP);
+  __ LoadIsolate(R0, kNoPP);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
@@ -278,8 +276,7 @@
 
   __ EnterFrame(0);
 
-  // Load current Isolate pointer from Context structure into R0.
-  __ LoadFieldFromOffset(R0, CTX, Context::isolate_offset(), kNoPP);
+  __ LoadIsolate(R0, kNoPP);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
@@ -1054,14 +1051,6 @@
     // R1: number of context variables as integer value (not object).
     __ StoreFieldToOffset(R1, R0, Context::num_variables_offset(), kNoPP);
 
-    // Setup isolate field.
-    // Load Isolate pointer into R2.
-    // R0: new object.
-    // R1: number of context variables.
-    __ LoadIsolate(R2, kNoPP);
-    // R2: isolate, not an object.
-    __ StoreFieldToOffset(R2, R0, Context::isolate_offset(), kNoPP);
-
     // Setup the parent field.
     // R0: new object.
     // R1: number of context variables.
@@ -1836,7 +1825,7 @@
     Assembler* assembler) {
   // Check single stepping.
   Label stepping, done_stepping;
-  __ LoadFieldFromOffset(R1, CTX, Context::isolate_offset(), kNoPP);
+  __ LoadIsolate(R1, kNoPP);
   __ LoadFromOffset(
       R1, R1, Isolate::single_step_offset(), kNoPP, kUnsignedByte);
   __ CompareImmediate(R1, 0, kNoPP);
@@ -2088,7 +2077,7 @@
     Assembler* assembler) {
   // Check single stepping.
   Label stepping, done_stepping;
-  __ LoadFieldFromOffset(R1, CTX, Context::isolate_offset(), kNoPP);
+  __ LoadIsolate(R1, kNoPP);
   __ LoadFromOffset(
       R1, R1, Isolate::single_step_offset(), kNoPP, kUnsignedByte);
   __ CompareImmediate(R1, 0, kNoPP);