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vm: Abstract working with tagged pointers in VM using macro accessors.

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Based on issues raised during recent review and inconsistency of different
implementations.
This commit is contained in:
Paul Sokolovsky 2014-03-22 23:20:07 +02:00
parent f357a19202
commit 1673420053
2 changed files with 14 additions and 9 deletions
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7
py/bc.h
View File

@ -8,7 +8,7 @@ typedef enum {
typedef struct _mp_exc_stack {
const byte *handler;
// bit 0 is saved currently_in_except_block value
machine_uint_t val_sp;
mp_obj_t *val_sp;
// We might only have 2 interesting cases here: SETUP_EXCEPT & SETUP_FINALLY,
// consider storing it in bit 1 of val_sp. TODO: SETUP_WITH?
byte opcode;
@ -17,3 +17,8 @@ typedef struct _mp_exc_stack {
mp_vm_return_kind_t mp_execute_byte_code(const byte *code, const mp_obj_t *args, uint n_args, const mp_obj_t *args2, uint n_args2, uint n_state, mp_obj_t *ret);
mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **ip_in_out, mp_obj_t *fastn, mp_obj_t **sp_in_out, mp_exc_stack *exc_stack, mp_exc_stack **exc_sp_in_out, volatile mp_obj_t inject_exc);
void mp_byte_code_print(const byte *code, int len);
// Helper macros to access pointer with least significant bit holding a flag
#define MP_TAGPTR_PTR(x) ((void*)((machine_uint_t)(x) & ~((machine_uint_t)1)))
#define MP_TAGPTR_TAG(x) ((machine_uint_t)(x) & 1)
#define MP_TAGPTR_MAKE(ptr, tag) ((void*)((machine_uint_t)(ptr) | tag))

16
py/vm.c
View File

@ -118,8 +118,8 @@ mp_vm_return_kind_t mp_execute_byte_code_2(const byte *code_info, const byte **i
mp_obj_t obj1, obj2;
nlr_buf_t nlr;
volatile machine_uint_t currently_in_except_block = (machine_uint_t)*exc_sp_in_out & 1; // 0 or 1, to detect nested exceptions
mp_exc_stack *volatile exc_sp = (void*)((machine_uint_t)*exc_sp_in_out & ~1); // stack grows up, exc_sp points to top of stack
volatile bool currently_in_except_block = MP_TAGPTR_TAG(*exc_sp_in_out); // 0 or 1, to detect nested exceptions
mp_exc_stack *volatile exc_sp = MP_TAGPTR_PTR(*exc_sp_in_out); // stack grows up, exc_sp points to top of stack
const byte *volatile save_ip = ip; // this is so we can access ip in the exception handler without making ip volatile (which means the compiler can't keep it in a register in the main loop)
// outer exception handling loop
@ -387,7 +387,7 @@ unwind_jump:
++exc_sp;
exc_sp->opcode = op;
exc_sp->handler = ip + unum;
exc_sp->val_sp = (((machine_uint_t)sp) | currently_in_except_block);
exc_sp->val_sp = MP_TAGPTR_MAKE(sp, currently_in_except_block);
currently_in_except_block = 0; // in a try block now
break;
@ -437,7 +437,7 @@ unwind_jump:
case MP_BC_POP_BLOCK:
// we are exiting an exception handler, so pop the last one of the exception-stack
assert(exc_sp >= exc_stack);
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
currently_in_except_block = MP_TAGPTR_TAG(exc_sp->val_sp); // restore previous state
exc_sp--; // pop back to previous exception handler
break;
@ -449,7 +449,7 @@ unwind_jump:
assert(currently_in_except_block);
//sp = (mp_obj_t*)(*exc_sp--);
//exc_sp--; // discard ip
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
currently_in_except_block = MP_TAGPTR_TAG(exc_sp->val_sp); // restore previous state
exc_sp--; // pop back to previous exception handler
//sp -= 3; // pop 3 exception values
break;
@ -607,7 +607,7 @@ unwind_return:
nlr_pop();
*ip_in_out = ip;
*sp_in_out = sp;
*exc_sp_in_out = (void*)((machine_uint_t)exc_sp | currently_in_except_block);
*exc_sp_in_out = MP_TAGPTR_MAKE(exc_sp, currently_in_except_block);
return MP_VM_RETURN_YIELD;
case MP_BC_IMPORT_NAME:
@ -663,7 +663,7 @@ unwind_return:
// at the moment we are just raising the very last exception (the one that caused the nested exception)
// move up to previous exception handler
currently_in_except_block = (exc_sp->val_sp & 1); // restore previous state
currently_in_except_block = MP_TAGPTR_TAG(exc_sp->val_sp); // restore previous state
exc_sp--; // pop back to previous exception handler
}
@ -672,7 +672,7 @@ unwind_return:
currently_in_except_block = 1;
// catch exception and pass to byte code
sp = (mp_obj_t*)(exc_sp->val_sp & (~((machine_uint_t)1)));
sp = MP_TAGPTR_PTR(exc_sp->val_sp);
ip = exc_sp->handler;
// push(traceback, exc-val, exc-type)
PUSH(mp_const_none);