factor/vm/callstack.cpp

#include "master.hpp"

namespace factor {

// Allocates memory (allot)
callstack* factor_vm::allot_callstack(cell size) {
  callstack* stack = allot<callstack>(callstack_object_size(size));
  stack->length = tag_fixnum(size);
  return stack;
}

// We ignore the two topmost frames, the 'callstack' primitive
// frame itself, and the frame calling the 'callstack' primitive,
// so that set-callstack doesn't get stuck in an infinite loop.

// This means that if 'callstack' is called in tail position, we
// will have popped a necessary frame... however this word is only
// called by continuation implementation, and user code shouldn't
// 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 = code->frame_predecessor(frame_top);
    if (pred >= ctx->callstack_bottom)
      return frame_top;
    frame_top = pred;
  }
  return frame_top;
}

// Allocates memory (allot_callstack)
cell factor_vm::capture_callstack(context* ctx) {
  cell top = second_from_top_stack_frame(ctx);
  cell bottom = ctx->callstack_bottom;

  fixnum size = std::max((cell)0, bottom - top);

  callstack* stack = allot_callstack(size);
  memcpy(stack->top(), (void *)top, size);
  return tag<callstack>(stack);
}

// Allocates memory (capture_callstack)
void factor_vm::primitive_callstack_for() {
  context* other_ctx = (context*)pinned_alien_offset(ctx->peek());
  ctx->replace(capture_callstack(other_ctx));
}

// Allocates memory (frames.trim()), iterate_callstack_object()
void factor_vm::primitive_callstack_to_array() {
  data_root<callstack> callstack(ctx->peek(), this);
  // Allocates memory here.
  growable_array frames(this);

  auto stack_frame_accumulator = [&](cell frame_top,
                                     cell size,
                                     code_block* owner,
                                     cell addr) {
    (void)frame_top;
    (void)size;
    data_root<object> executing_quot(owner->owner_quot(), this);
    data_root<object> executing(owner->owner, this);
    data_root<object> scan(owner->scan(this, addr), this);

    frames.add(executing.value());
    frames.add(executing_quot.value());
    frames.add(scan.value());
  };
  iterate_callstack_object(callstack.untagged(), stack_frame_accumulator);

  frames.trim();

  ctx->replace(frames.elements.value());
}

// Some primitives implementing a limited form of callstack mutation.
// Used by the single stepper.
void factor_vm::primitive_innermost_stack_frame_executing() {
  callstack* stack = untag_check<callstack>(ctx->peek());
  void* frame = stack->top();
  cell addr = *(cell*)frame;
  ctx->replace(code->code_block_for_address(addr)->owner_quot());
}

void factor_vm::primitive_innermost_stack_frame_scan() {
  callstack* stack = untag_check<callstack>(ctx->peek());
  void* frame = stack->top();
  cell addr = *(cell*)frame;
  ctx->replace(code->code_block_for_address(addr)->scan(this, addr));
}

// Allocates memory (jit_compile_quotation)
void factor_vm::primitive_set_innermost_stack_frame_quotation() {
  data_root<callstack> stack(ctx->pop(), this);
  data_root<quotation> quot(ctx->pop(), this);

  check_tagged(stack);
  check_tagged(quot);

  jit_compile_quotation(quot.value(), true);

  void* inner = stack->top();
  cell addr = *(cell*)inner;
  code_block* block = code->code_block_for_address(addr);
  cell offset = block->offset(addr);
  *(cell*)inner = quot->entry_point + offset;
}

// Allocates memory (allot_alien)
void factor_vm::primitive_callstack_bounds() {
  ctx->push(allot_alien(ctx->callstack_seg->start));
  ctx->push(allot_alien(ctx->callstack_seg->end));
}

}