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py/emitnative: Add support for return/break/continue in try and with. 

This patch adds full support for unwinding jumps to the native emitter.
This means that return/break/continue can be used in try-except,
try-finally and with statements.  For code that doesn't use unwinding jumps
there is almost no overhead added to the generated code.
This commit is contained in:
Damien George 2018-09-04 14:31:28 +10:00
parent 3cd2c281d7
commit 4ae7111573
7 changed files with 146 additions and 38 deletions
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8
py/compile.c
View File

@ -1595,6 +1595,7 @@ STATIC void compile_try_except(compiler_t *comp, mp_parse_node_t pn_body, int n_
compile_decrease_except_level(comp);
EMIT(end_finally);
reserve_labels_for_native(comp, 1);
}
EMIT_ARG(jump, l2);
EMIT_ARG(label_assign, end_finally_label);
@ -1603,6 +1604,7 @@ STATIC void compile_try_except(compiler_t *comp, mp_parse_node_t pn_body, int n_
compile_decrease_except_level(comp);
EMIT(end_finally);
reserve_labels_for_native(comp, 1);
EMIT(end_except_handler);
EMIT_ARG(label_assign, success_label);
@ -1631,6 +1633,7 @@ STATIC void compile_try_finally(compiler_t *comp, mp_parse_node_t pn_body, int n
compile_decrease_except_level(comp);
EMIT(end_finally);
reserve_labels_for_native(comp, 1);
}
STATIC void compile_try_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
@ -1683,9 +1686,10 @@ STATIC void compile_with_stmt_helper(compiler_t *comp, int n, mp_parse_node_t *n
compile_with_stmt_helper(comp, n - 1, nodes + 1, body);
// finish this with block
EMIT_ARG(with_cleanup, l_end);
reserve_labels_for_native(comp, 2); // used by native's with_cleanup
reserve_labels_for_native(comp, 3); // used by native's with_cleanup
compile_decrease_except_level(comp);
EMIT(end_finally);
reserve_labels_for_native(comp, 1);
}
}
@ -1752,6 +1756,7 @@ STATIC void compile_async_for_stmt(compiler_t *comp, mp_parse_node_struct_t *pns
EMIT_ARG(adjust_stack_size, 1); // if we jump here, the exc is on the stack
compile_decrease_except_level(comp);
EMIT(end_finally);
reserve_labels_for_native(comp, 1);
EMIT(end_except_handler);
EMIT_ARG(label_assign, try_else_label);
@ -1879,6 +1884,7 @@ STATIC void compile_async_with_stmt_helper(compiler_t *comp, int n, mp_parse_nod
EMIT_ARG(label_assign, l_end);
compile_decrease_except_level(comp);
EMIT(end_finally);
reserve_labels_for_native(comp, 1);
}
}

6
py/emitnarm.c
View File

@ -8,8 +8,10 @@
#define GENERIC_ASM_API (1)
#include "py/asmarm.h"
// Word index of REG_LOCAL_1(=r4) in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (3)
// Word indices of REG_LOCAL_x in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (3) // r4
#define NLR_BUF_IDX_LOCAL_2 (4) // r5
#define NLR_BUF_IDX_LOCAL_3 (5) // r6
#define N_ARM (1)
#define EXPORT_FUN(name) emit_native_arm_##name

144
py/emitnative.c
View File

@ -85,6 +85,8 @@
// Indices within the local C stack for various variables
#define LOCAL_IDX_EXC_VAL(emit) ((emit)->stack_start + NLR_BUF_IDX_RET_VAL)
#define LOCAL_IDX_EXC_HANDLER_PC(emit) ((emit)->stack_start + NLR_BUF_IDX_LOCAL_1)
#define LOCAL_IDX_EXC_HANDLER_UNWIND(emit) ((emit)->stack_start + NLR_BUF_IDX_LOCAL_2)
#define LOCAL_IDX_RET_VAL(emit) ((emit)->stack_start + NLR_BUF_IDX_LOCAL_3)
#define LOCAL_IDX_LOCAL_VAR(emit, local_num) ((emit)->stack_start + (emit)->n_state - 1 - (local_num))
// number of arguments to viper functions are limited to this value
@ -148,9 +150,14 @@ typedef struct _stack_info_t {
} data;
} stack_info_t;
#define UNWIND_LABEL_UNUSED (0x7fff)
#define UNWIND_LABEL_DO_FINAL_UNWIND (0x7ffe)
typedef struct _exc_stack_entry_t {
uint16_t label : 15;
uint16_t is_finally : 1;
uint16_t unwind_label : 15;
uint16_t is_active : 1;
} exc_stack_entry_t;
struct _emit_t {
@ -843,27 +850,44 @@ STATIC void emit_native_push_exc_stack(emit_t *emit, uint label, bool is_finally
exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size++];
e->label = label;
e->is_finally = is_finally;
e->unwind_label = UNWIND_LABEL_UNUSED;
e->is_active = true;
ASM_MOV_REG_PCREL(emit->as, REG_RET, label);
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
}
STATIC void emit_native_pop_exc_stack(emit_t *emit, bool do_pop) {
STATIC void emit_native_leave_exc_stack(emit_t *emit, bool start_of_handler) {
assert(emit->exc_stack_size > 0);
if (emit->exc_stack_size == 1) {
if (do_pop) {
--emit->exc_stack_size;
// Get current exception handler and deactivate it
exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size - 1];
e->is_active = false;
// Find next innermost active exception handler, to restore as current handler
for (--e; e >= emit->exc_stack && !e->is_active; --e) {
}
// Update the PC of the new exception handler
if (e < emit->exc_stack) {
// No active handler, clear handler PC to zero
if (start_of_handler) {
// Optimisation: PC is already cleared by global exc handler
return;
}
ASM_XOR_REG_REG(emit->as, REG_RET, REG_RET);
} else {
uint label = emit->exc_stack[emit->exc_stack_size - 2].label;
ASM_MOV_REG_PCREL(emit->as, REG_RET, label);
// Found new active handler, get its PC
ASM_MOV_REG_PCREL(emit->as, REG_RET, e->label);
}
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
if (do_pop) {
--emit->exc_stack_size;
}
STATIC exc_stack_entry_t *emit_native_pop_exc_stack(emit_t *emit) {
assert(emit->exc_stack_size > 0);
exc_stack_entry_t *e = &emit->exc_stack[--emit->exc_stack_size];
assert(e->is_active == false);
return e;
}
STATIC void emit_native_label_assign(emit_t *emit, mp_uint_t l) {
@ -890,7 +914,7 @@ STATIC void emit_native_label_assign(emit_t *emit, mp_uint_t l) {
if (is_finally) {
// Label is at start of finally handler: pop exception stack
emit_native_pop_exc_stack(emit, true);
emit_native_leave_exc_stack(emit, true);
}
}
@ -904,13 +928,19 @@ STATIC void emit_native_global_exc_entry(emit_t *emit) {
mp_uint_t start_label = *emit->label_slot + 2;
mp_uint_t global_except_label = *emit->label_slot + 3;
// Clear the unwind state
ASM_XOR_REG_REG(emit->as, REG_TEMP0, REG_TEMP0);
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_TEMP0);
// Put PC of start code block into REG_LOCAL_1
ASM_MOV_REG_PCREL(emit->as, REG_LOCAL_1, start_label);
// 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));
emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_1, sizeof(nlr_buf_t) / sizeof(uintptr_t));
emit_call(emit, MP_F_NLR_PUSH);
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
@ -937,15 +967,12 @@ STATIC void emit_native_global_exc_exit(emit_t *emit) {
emit_native_label_assign(emit, emit->exit_label);
if (NEED_GLOBAL_EXC_HANDLER(emit)) {
// Save return value
ASM_MOV_REG_REG(emit->as, REG_LOCAL_1, REG_RET);
// Pop the nlr context
emit_call(emit, MP_F_NLR_POP);
adjust_stack(emit, -(mp_int_t)(sizeof(nlr_buf_t) / sizeof(uintptr_t)));
// Restore return value
ASM_MOV_REG_REG(emit->as, REG_RET, REG_LOCAL_1);
// Load return value
ASM_MOV_REG_LOCAL(emit->as, REG_RET, LOCAL_IDX_RET_VAL(emit));
}
ASM_EXIT(emit->as);
@ -1717,8 +1744,46 @@ STATIC void emit_native_jump_if_or_pop(emit_t *emit, bool cond, mp_uint_t label)
}
STATIC void emit_native_unwind_jump(emit_t *emit, mp_uint_t label, mp_uint_t except_depth) {
(void)except_depth;
emit_native_jump(emit, label & ~MP_EMIT_BREAK_FROM_FOR); // TODO properly
if (except_depth > 0) {
exc_stack_entry_t *first_finally = NULL;
exc_stack_entry_t *prev_finally = NULL;
exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size - 1];
for (; except_depth > 0; --except_depth, --e) {
if (e->is_finally && e->is_active) {
// Found an active finally handler
if (first_finally == NULL) {
first_finally = e;
}
if (prev_finally != NULL) {
// Mark prev finally as needed to unwind a jump
prev_finally->unwind_label = e->label;
}
prev_finally = e;
}
}
if (prev_finally == NULL) {
// No finally, handle the jump ourselves
// First, restore the exception handler address for the jump
if (e < emit->exc_stack) {
ASM_XOR_REG_REG(emit->as, REG_RET, REG_RET);
} else {
ASM_MOV_REG_PCREL(emit->as, REG_RET, e->label);
}
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
} else {
// Last finally should do our jump for us
// Mark finally as needing to decide the type of jump
prev_finally->unwind_label = UNWIND_LABEL_DO_FINAL_UNWIND;
ASM_MOV_REG_PCREL(emit->as, REG_RET, label & ~MP_EMIT_BREAK_FROM_FOR);
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_RET);
// Cancel any active exception (see also emit_native_pop_except)
ASM_MOV_REG_IMM(emit->as, REG_RET, (mp_uint_t)mp_const_none);
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_RET);
// Jump to the innermost active finally
label = first_finally->label;
}
}
emit_native_jump(emit, label & ~MP_EMIT_BREAK_FROM_FOR);
}
STATIC void emit_native_setup_with(emit_t *emit, mp_uint_t label) {
@ -1754,7 +1819,7 @@ STATIC void emit_native_setup_with(emit_t *emit, mp_uint_t label) {
// need to commit stack because we may jump elsewhere
need_stack_settled(emit);
emit_native_push_exc_stack(emit, label, false);
emit_native_push_exc_stack(emit, label, true);
emit_native_dup_top(emit);
// stack: (..., __exit__, self, as_value, as_value)
@ -1773,14 +1838,17 @@ STATIC void emit_native_setup_block(emit_t *emit, mp_uint_t label, int kind) {
}
STATIC void emit_native_with_cleanup(emit_t *emit, mp_uint_t label) {
// Note: 2 labels are reserved for this function, starting at *emit->label_slot
// Note: 3 labels are reserved for this function, starting at *emit->label_slot
// stack: (..., __exit__, self, as_value)
emit_native_pre(emit);
emit_native_pop_exc_stack(emit, false);
emit_native_leave_exc_stack(emit, false);
adjust_stack(emit, -1);
// stack: (..., __exit__, self)
// Label for case where __exit__ is called from an unwind jump
emit_native_label_assign(emit, *emit->label_slot + 2);
// call __exit__
emit_post_push_imm(emit, VTYPE_PYOBJ, (mp_uint_t)mp_const_none);
emit_post_push_imm(emit, VTYPE_PYOBJ, (mp_uint_t)mp_const_none);
@ -1792,16 +1860,22 @@ STATIC void emit_native_with_cleanup(emit_t *emit, mp_uint_t label) {
emit_native_jump(emit, *emit->label_slot);
// nlr_catch
emit_native_label_assign(emit, label);
// Don't use emit_native_label_assign because this isn't a real finally label
mp_asm_base_label_assign(&emit->as->base, label);
// Pop with's exception handler
emit_native_pop_exc_stack(emit, true);
// Leave with's exception handler
emit_native_leave_exc_stack(emit, true);
// Adjust stack counter for: __exit__, self (implicitly discard as_value which is above self)
emit_native_adjust_stack_size(emit, 2);
// stack: (..., __exit__, self)
ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit)); // get exc
// Check if exc is None and jump to non-exc handler if it is
ASM_MOV_REG_IMM(emit->as, REG_ARG_2, (mp_uint_t)mp_const_none);
ASM_JUMP_IF_REG_EQ(emit->as, REG_ARG_1, REG_ARG_2, *emit->label_slot + 2);
ASM_LOAD_REG_REG_OFFSET(emit->as, REG_ARG_2, REG_ARG_1, 0); // get type(exc)
emit_post_push_reg(emit, VTYPE_PYOBJ, REG_ARG_2); // push type(exc)
emit_post_push_reg(emit, VTYPE_PYOBJ, REG_ARG_1); // push exc value
@ -1840,6 +1914,20 @@ STATIC void emit_native_end_finally(emit_t *emit) {
emit_native_pre(emit);
ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit));
emit_call(emit, MP_F_NATIVE_RAISE);
// Get state for this finally and see if we need to unwind
exc_stack_entry_t *e = emit_native_pop_exc_stack(emit);
if (e->unwind_label != UNWIND_LABEL_UNUSED) {
ASM_MOV_REG_LOCAL(emit->as, REG_RET, LOCAL_IDX_EXC_HANDLER_UNWIND(emit));
ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, *emit->label_slot, false);
if (e->unwind_label == UNWIND_LABEL_DO_FINAL_UNWIND) {
ASM_JUMP_REG(emit->as, REG_RET);
} else {
emit_native_jump(emit, e->unwind_label);
}
emit_native_label_assign(emit, *emit->label_slot);
}
emit_post(emit);
}
@ -1886,7 +1974,7 @@ STATIC void emit_native_for_iter_end(emit_t *emit) {
STATIC void emit_native_pop_block(emit_t *emit) {
emit_native_pre(emit);
if (!emit->exc_stack[emit->exc_stack_size - 1].is_finally) {
emit_native_pop_exc_stack(emit, false);
emit_native_leave_exc_stack(emit, false);
}
emit_post(emit);
}
@ -2314,8 +2402,12 @@ STATIC void emit_native_return_value(emit_t *emit) {
emit_pre_pop_reg(emit, &vtype, REG_RET);
assert(vtype == VTYPE_PYOBJ);
}
if (NEED_GLOBAL_EXC_HANDLER(emit)) {
// Save return value for the global exception handler to use
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_RET_VAL(emit), REG_RET);
}
emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size);
emit->last_emit_was_return_value = true;
ASM_JUMP(emit->as, emit->exit_label);
}
STATIC void emit_native_raise_varargs(emit_t *emit, mp_uint_t n_args) {
@ -2337,8 +2429,8 @@ STATIC void emit_native_yield(emit_t *emit, int kind) {
}
STATIC void emit_native_start_except_handler(emit_t *emit) {
// Protected block has finished so pop the exception stack
emit_native_pop_exc_stack(emit, true);
// Protected block has finished so leave the current exception handler
emit_native_leave_exc_stack(emit, true);
// Get and push nlr_buf.ret_val
ASM_MOV_REG_LOCAL(emit->as, REG_TEMP0, LOCAL_IDX_EXC_VAL(emit));

6
py/emitnthumb.c
View File

@ -8,8 +8,10 @@
#define GENERIC_ASM_API (1)
#include "py/asmthumb.h"
// Word index of REG_LOCAL_1(=r4) in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (3)
// Word indices of REG_LOCAL_x in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (3) // r4
#define NLR_BUF_IDX_LOCAL_2 (4) // r5
#define NLR_BUF_IDX_LOCAL_3 (5) // r6
#define N_THUMB (1)
#define EXPORT_FUN(name) emit_native_thumb_##name

6
py/emitnx64.c
View File

@ -8,8 +8,10 @@
#define GENERIC_ASM_API (1)
#include "py/asmx64.h"
// Word index of REG_LOCAL_1(=rbx) in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (5)
// Word indices of REG_LOCAL_x in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (5) // rbx
#define NLR_BUF_IDX_LOCAL_2 (6) // r12
#define NLR_BUF_IDX_LOCAL_3 (7) // r13
#define N_X64 (1)
#define EXPORT_FUN(name) emit_native_x64_##name

6
py/emitnx86.c
View File

@ -9,8 +9,10 @@
#define GENERIC_ASM_API (1)
#include "py/asmx86.h"
// Word index of REG_LOCAL_1(=ebx) in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (5)
// Word indices of REG_LOCAL_x in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (5) // ebx
#define NLR_BUF_IDX_LOCAL_2 (7) // esi
#define NLR_BUF_IDX_LOCAL_3 (6) // edi
// x86 needs a table to know how many args a given function has
STATIC byte mp_f_n_args[MP_F_NUMBER_OF] = {

6
py/emitnxtensa.c
View File

@ -8,8 +8,10 @@
#define GENERIC_ASM_API (1)
#include "py/asmxtensa.h"
// Word index of REG_LOCAL_1(=a12) in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (8)
// Word indices of REG_LOCAL_x in nlr_buf_t
#define NLR_BUF_IDX_LOCAL_1 (8) // a12
#define NLR_BUF_IDX_LOCAL_2 (9) // a13
#define NLR_BUF_IDX_LOCAL_3 (10) // a14
#define N_XTENSA (1)
#define EXPORT_FUN(name) emit_native_xtensa_##name