parrotcode: Register handling routines | |
Contents | C |
src/gc/register.c - Register handling routines
Parrot has 4 register sets, one for each of its basic types. The number of registers in each set varies depending on the use counts of the subroutine and is determined by the PASM/PIR compiler in the register allocation pass (imcc/reg_alloc.c).
There is one register stack to support the saveall
and restoreall
opcodes.
The former copies all registers to newly allocated storage and points the register base pointers to this storage.
In Parrot_pop_regs
the register base pointers are restored to the previous values and the allocated register memory is discarded.
+----------++----+------+------------+----+
| context || N | I | P | S +
+----------++----+------+------------+----+
^ ^ ^ ^
| | ctx.bp ctx.bp_ps
ctx.state opt
padding
Registers are addressed as usual via the register base pointer ctx.bp.
The macro CONTEXT() hides these details
There are two allocation strategies: chunked memory and malloced with a free list.
CHUNKED_CTX_MEM = 1
ctx_mem.data
is a pointer to an allocated chunk of memory. The pointer ctx_mem.free
holds the next usable location. With (full) continuations the ctx_mem.free
pointer can't be moved below the ctx_mem.threshold
, which is the highest context pointer of all active continuations. [the code for this is incomplete; it had suffered some bit-rot and was getting in the way of maintaining the other case. -- rgr, 4-Feb-06.]
RT#46177 GC has to lower this threshold when collecting continuations.
CHUNKED_CTX_MEM = 0
Context/register memory is malloced. ctx_mem.free
is used as a free list of reusable items.
Round register allocation size up to the nearest multiple of 8. A granularity of 8 is arbitrary, it could have been some bigger power of 2. A "slot" is an index into the free_list array. Each slot in free_list has a linked list of pointers to already allocated contexts available for (re)use. The slot where an available context is stored corresponds to the size of the context.
void destroy_context
void create_initial_context
void parrot_gc_context
static void clear_regs
static void init_context
struct Parrot_Context *Parrot_dup_context
struct Parrot_Context *Parrot_push_context
caller_ctx
, suitable to use with Parrot_pop_context
.void Parrot_pop_context
Parrot_push_context
and restore the previous context.struct Parrot_Context *Parrot_alloc_context
n_regs_used
is copied. The function returns the new context.void Parrot_free_context
re_use
is true, this function is called by a return continuation invoke, else from the destructor of a continuation.void Parrot_set_context_threshold
void setup_register_stacks
void Parrot_push_regs
void Parrot_pop_regs
void mark_register_stack
void Parrot_clear_i
void Parrot_clear_s
void Parrot_clear_p
void Parrot_clear_n
include/parrot/register.h and src/stack_common.c
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