factor/vm/cpu-x86.hpp

namespace factor
{

inline static void* frame_return_address(void *frame_top)
{
	return *(void**)frame_top;
}

inline static void set_frame_return_address(void *frame_top, void *return_address)
{
	*(void**)frame_top = return_address;
}

#define CALLSTACK_BOTTOM(ctx) (void *)(ctx->callstack_seg->end - sizeof(cell) * 5)

inline static void flush_icache(cell start, cell len) {}

/* In the instruction sequence:

   MOV EBX,...
   JMP blah

   the offset from the immediate operand to MOV to the instruction after
   the jump is a cell for the immediate operand, 4 bytes for the JMP
   destination, and one byte for the JMP opcode. */
static const fixnum xt_tail_pic_offset = 4 + 1;

static const unsigned char call_opcode = 0xe8;
static const unsigned char jmp_opcode = 0xe9;

inline static unsigned char call_site_opcode(cell return_address)
{
	return *(unsigned char *)(return_address - 5);
}

inline static void check_call_site(cell return_address)
{
	unsigned char opcode = call_site_opcode(return_address);
	FACTOR_ASSERT(opcode == call_opcode || opcode == jmp_opcode);
	(void)opcode; // suppress warning when compiling without assertions
}

inline static void *get_call_target(cell return_address)
{
	check_call_site(return_address);
	return (void *)(*(int *)(return_address - 4) + return_address);
}

inline static void set_call_target(cell return_address, void *target)
{
	check_call_site(return_address);
	*(int *)(return_address - 4) = (u32)((cell)target - return_address);
}

inline static bool tail_call_site_p(cell return_address)
{
	switch(call_site_opcode(return_address))
	{
	case jmp_opcode: return true;
	case call_opcode: return false;
	default: abort(); return false;
	}
}

inline static unsigned int fpu_status(unsigned int status)
{
	unsigned int r = 0;
	
	if (status & 0x01)
		r |= FP_TRAP_INVALID_OPERATION;
	if (status & 0x04)
		r |= FP_TRAP_ZERO_DIVIDE;
	if (status & 0x08)
		r |= FP_TRAP_OVERFLOW;
	if (status & 0x10)
		r |= FP_TRAP_UNDERFLOW;
	if (status & 0x20)
		r |= FP_TRAP_INEXACT;

	return r;
}

}