VM: move the frame_predecessor() method to the code_heap class

vm/callstack.cpp

@@ -20,7 +20,7 @@ be calling it at all, so we leave it as it is for now. */
 cell factor_vm::second_from_top_stack_frame(context* ctx) {
   cell frame_top = ctx->callstack_top;
   for (cell i = 0; i < 2; ++i) {
-    cell pred = frame_predecessor(frame_top);
+    cell pred = code->frame_predecessor(frame_top);
     if (pred >= ctx->callstack_bottom)
       return frame_top;
     frame_top = pred;
@@ -49,14 +49,6 @@ void factor_vm::primitive_callstack_for() {
   ctx->replace(capture_callstack(other_ctx));
 }
 
-cell factor_vm::frame_predecessor(cell frame_top) {
-  cell addr = *(cell*)frame_top;
-  FACTOR_ASSERT(addr != 0);
-  code_block* owner = code->code_block_for_address(addr);
-  cell frame_size = owner->stack_frame_size_for_address(addr);
-  return frame_top + frame_size;
-}
-
 struct stack_frame_in_array {
   cell cells[3];
 };

vm/code_heap.cpp

@@ -83,6 +83,16 @@ code_block* code_heap::code_block_for_address(cell address) {
   return found_block;
 }
 
+cell code_heap::frame_predecessor(cell frame_top) {
+  cell addr = *(cell*)frame_top;
+  FACTOR_ASSERT(seg->in_segment_p(addr));
+  //FACTOR_ASSERT(addr != 0);
+  code_block* owner = code_block_for_address(addr);
+  cell frame_size = owner->stack_frame_size_for_address(addr);
+  return frame_top + frame_size;
+}
+
+/* Recomputes the all_blocks set of code blocks */
 void code_heap::initialize_all_blocks_set() {
   all_blocks.clear();
   auto all_blocks_set_inserter = [&](code_block* block, cell size) {

vm/code_heap.hpp

@@ -47,6 +47,7 @@ struct code_heap {
   void sweep();
 
   code_block* code_block_for_address(cell address);
+  cell frame_predecessor(cell frame_top);
 
   bool safepoint_p(cell addr) {
     cell page_mask = ~(getpagesize() - 1);

vm/cpu-x86.cpp

@@ -17,7 +17,7 @@ void factor_vm::dispatch_signal_handler(cell* sp, cell* pc, cell handler) {
     cell frame_top = ctx->callstack_top;
 
     while (frame_top < ctx->callstack_bottom && frame_top < callstack_limit) {
-      frame_top = frame_predecessor(frame_top);
+      frame_top = code->frame_predecessor(frame_top);
     }
 
     *sp = frame_top;

vm/vm.hpp

@@ -628,7 +628,6 @@ struct factor_vm {
   cell capture_callstack(context* ctx);
   void primitive_callstack();
   void primitive_callstack_for();
-  cell frame_predecessor(cell frame_top);
   void primitive_callstack_to_array();
   void primitive_innermost_stack_frame_executing();
   void primitive_innermost_stack_frame_scan();