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py/emitnative: Provide dedicated local for exception unwind handler ptr. 

This eliminates the need to save and restore the exception unwind handler
pointer when calling nlr_push.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2022-05-19 15:08:45 +10:00
parent b608964804
commit 7883ae413d
1 changed files with 15 additions and 6 deletions
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21
py/emitnative.c
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@ -63,12 +63,14 @@
// C stack layout for native functions:
// 0: nlr_buf_t [optional]
// exc_handler_unwind [optional word]
// emit->code_state_start: mp_code_state_native_t
// emit->stack_start: Python object stack | emit->n_state
// locals (reversed, L0 at end) |
//
// C stack layout for native generator functions:
// 0=emit->stack_start: nlr_buf_t
// exc_handler_unwind [optional word]
//
// Then REG_GENERATOR_STATE points to:
// 0=emit->code_state_start: mp_code_state_native_t
@ -77,6 +79,7 @@
//
// C stack layout for viper functions:
// 0: nlr_buf_t [optional]
// exc_handler_unwind [optional word]
// emit->code_state_start: fun_obj, old_globals [optional]
// emit->stack_start: Python object stack | emit->n_state
// locals (reversed, L0 at end) |
@ -120,6 +123,9 @@
#define NEED_GLOBAL_EXC_HANDLER(emit) ((emit)->scope->exc_stack_size > 0 \
|| ((emit)->scope->scope_flags & (MP_SCOPE_FLAG_GENERATOR | MP_SCOPE_FLAG_REFGLOBALS)))
// Whether a slot is needed to store LOCAL_IDX_EXC_HANDLER_UNWIND
#define NEED_EXC_HANDLER_UNWIND(emit) ((emit)->scope->exc_stack_size > 0)
// Whether registers can be used to store locals (only true if there are no
// exception handlers, because otherwise an nlr_jump will restore registers to
// their state at the start of the function and updates to locals will be lost)
@ -128,7 +134,7 @@
// Indices within the local C stack for various variables
#define LOCAL_IDX_EXC_VAL(emit) (NLR_BUF_IDX_RET_VAL)
#define LOCAL_IDX_EXC_HANDLER_PC(emit) (NLR_BUF_IDX_LOCAL_1)
#define LOCAL_IDX_EXC_HANDLER_UNWIND(emit) (NLR_BUF_IDX_LOCAL_2)
#define LOCAL_IDX_EXC_HANDLER_UNWIND(emit) (SIZEOF_NLR_BUF) // this needs a dedicated variable outside nlr_buf_t
#define LOCAL_IDX_RET_VAL(emit) (NLR_BUF_IDX_LOCAL_3)
#define LOCAL_IDX_FUN_OBJ(emit) ((emit)->code_state_start + OFFSETOF_CODE_STATE_FUN_BC)
#define LOCAL_IDX_OLD_GLOBALS(emit) ((emit)->code_state_start + OFFSETOF_CODE_STATE_IP)
@ -403,6 +409,9 @@ STATIC void emit_native_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scop
emit->code_state_start = 0;
if (NEED_GLOBAL_EXC_HANDLER(emit)) {
emit->code_state_start = SIZEOF_NLR_BUF;
if (NEED_EXC_HANDLER_UNWIND(emit)) {
emit->code_state_start += 1;
}
}
size_t fun_table_off = mp_emit_common_use_const_obj(emit->emit_common, MP_OBJ_FROM_PTR(&mp_fun_table));
@ -498,11 +507,13 @@ STATIC void emit_native_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scop
emit->n_state = scope->num_locals + scope->stack_size;
if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
emit->code_state_start = 0;
emit->stack_start = SIZEOF_CODE_STATE;
mp_asm_base_data(&emit->as->base, ASM_WORD_SIZE, (uintptr_t)emit->prelude_ptr_index);
mp_asm_base_data(&emit->as->base, ASM_WORD_SIZE, (uintptr_t)emit->start_offset);
ASM_ENTRY(emit->as, SIZEOF_NLR_BUF);
ASM_ENTRY(emit->as, emit->code_state_start);
// Reset the state size for the state pointed to by REG_GENERATOR_STATE
emit->code_state_start = 0;
emit->stack_start = SIZEOF_CODE_STATE;
// Put address of code_state into REG_GENERATOR_STATE
#if N_X86
@ -1188,14 +1199,12 @@ STATIC void emit_native_global_exc_entry(emit_t *emit) {
// Wrap everything in an nlr context
emit_native_label_assign(emit, nlr_label);
ASM_MOV_REG_LOCAL(emit->as, REG_LOCAL_2, LOCAL_IDX_EXC_HANDLER_UNWIND(emit));
ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, 0);
emit_call(emit, MP_F_NLR_PUSH);
#if N_NLR_SETJMP
ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, 2);
emit_call(emit, MP_F_SETJMP);
#endif
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_LOCAL_2);
ASM_JUMP_IF_REG_NONZERO(emit->as, REG_RET, global_except_label, true);
// Clear PC of current code block, and jump there to resume execution