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py/emit: Remove logic to detect last-emit-was-return-value.

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This optimisation to remove dead code is not as good as it could be.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2022-06-17 23:06:24 +10:00
parent 0db046b67b
commit e85a096302
5 changed files with 16 additions and 48 deletions
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24
py/compile.c
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@ -1330,12 +1330,8 @@ STATIC void compile_if_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
goto done; goto done;
} }
if ( // optimisation: don't jump over non-existent elif/else blocks
// optimisation: don't jump over non-existent elif/else blocks if (!(MP_PARSE_NODE_IS_NULL(pns->nodes[2]) && MP_PARSE_NODE_IS_NULL(pns->nodes[3]))) {
!(MP_PARSE_NODE_IS_NULL(pns->nodes[2]) && MP_PARSE_NODE_IS_NULL(pns->nodes[3]))
// optimisation: don't jump if last instruction was return
&& !EMIT(last_emit_was_return_value)
) {
// jump over elif/else blocks // jump over elif/else blocks
EMIT_ARG(jump, l_end); EMIT_ARG(jump, l_end);
} }
@ -1362,10 +1358,7 @@ STATIC void compile_if_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
goto done; goto done;
} }
// optimisation: don't jump if last instruction was return EMIT_ARG(jump, l_end);
if (!EMIT(last_emit_was_return_value)) {
EMIT_ARG(jump, l_end);
}
EMIT_ARG(label_assign, l_fail); EMIT_ARG(label_assign, l_fail);
} }
} }
@ -1580,9 +1573,7 @@ STATIC void compile_for_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
EMIT_ARG(for_iter, pop_label); EMIT_ARG(for_iter, pop_label);
c_assign(comp, pns->nodes[0], ASSIGN_STORE); // variable c_assign(comp, pns->nodes[0], ASSIGN_STORE); // variable
compile_node(comp, pns->nodes[2]); // body compile_node(comp, pns->nodes[2]); // body
if (!EMIT(last_emit_was_return_value)) { EMIT_ARG(jump, continue_label);
EMIT_ARG(jump, continue_label);
}
EMIT_ARG(label_assign, pop_label); EMIT_ARG(label_assign, pop_label);
EMIT(for_iter_end); EMIT(for_iter_end);
@ -3048,11 +3039,8 @@ STATIC bool compile_scope(compiler_t *comp, scope_t *scope, pass_kind_t pass) {
} }
compile_node(comp, pns->nodes[3]); // 3 is function body compile_node(comp, pns->nodes[3]); // 3 is function body
// emit return if it wasn't the last opcode EMIT_ARG(load_const_tok, MP_TOKEN_KW_NONE);
if (!EMIT(last_emit_was_return_value)) { EMIT(return_value);
EMIT_ARG(load_const_tok, MP_TOKEN_KW_NONE);
EMIT(return_value);
}
} else if (scope->kind == SCOPE_LAMBDA) { } else if (scope->kind == SCOPE_LAMBDA) {
assert(MP_PARSE_NODE_IS_STRUCT(scope->pn)); assert(MP_PARSE_NODE_IS_STRUCT(scope->pn));
mp_parse_node_struct_t *pns = (mp_parse_node_struct_t *)scope->pn; mp_parse_node_struct_t *pns = (mp_parse_node_struct_t *)scope->pn;

2
py/emit.h
View File

@ -115,7 +115,6 @@ typedef struct _emit_method_table_t {
void (*start_pass)(emit_t *emit, pass_kind_t pass, scope_t *scope); void (*start_pass)(emit_t *emit, pass_kind_t pass, scope_t *scope);
bool (*end_pass)(emit_t *emit); bool (*end_pass)(emit_t *emit);
bool (*last_emit_was_return_value)(emit_t *emit);
void (*adjust_stack_size)(emit_t *emit, mp_int_t delta); void (*adjust_stack_size)(emit_t *emit, mp_int_t delta);
void (*set_source_line)(emit_t *emit, mp_uint_t line); void (*set_source_line)(emit_t *emit, mp_uint_t line);
@ -227,7 +226,6 @@ void emit_native_xtensawin_free(emit_t *emit);
void mp_emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope); void mp_emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope);
bool mp_emit_bc_end_pass(emit_t *emit); bool mp_emit_bc_end_pass(emit_t *emit);
bool mp_emit_bc_last_emit_was_return_value(emit_t *emit);
void mp_emit_bc_adjust_stack_size(emit_t *emit, mp_int_t delta); void mp_emit_bc_adjust_stack_size(emit_t *emit, mp_int_t delta);
void mp_emit_bc_set_source_line(emit_t *emit, mp_uint_t line); void mp_emit_bc_set_source_line(emit_t *emit, mp_uint_t line);

9
py/emitbc.c
View File

@ -47,7 +47,6 @@ struct _emit_t {
byte dummy_data[DUMMY_DATA_SIZE]; byte dummy_data[DUMMY_DATA_SIZE];
pass_kind_t pass : 8; pass_kind_t pass : 8;
mp_uint_t last_emit_was_return_value : 8;
int stack_size; int stack_size;
@ -272,7 +271,6 @@ STATIC void emit_write_bytecode_byte_label(emit_t *emit, int stack_adj, byte b1,
void mp_emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope) { void mp_emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope) {
emit->pass = pass; emit->pass = pass;
emit->stack_size = 0; emit->stack_size = 0;
emit->last_emit_was_return_value = false;
emit->scope = scope; emit->scope = scope;
emit->last_source_line_offset = 0; emit->last_source_line_offset = 0;
emit->last_source_line = 1; emit->last_source_line = 1;
@ -397,10 +395,6 @@ bool mp_emit_bc_end_pass(emit_t *emit) {
return true; return true;
} }
bool mp_emit_bc_last_emit_was_return_value(emit_t *emit) {
return emit->last_emit_was_return_value;
}
void mp_emit_bc_adjust_stack_size(emit_t *emit, mp_int_t delta) { void mp_emit_bc_adjust_stack_size(emit_t *emit, mp_int_t delta) {
if (emit->pass == MP_PASS_SCOPE) { if (emit->pass == MP_PASS_SCOPE) {
return; return;
@ -410,7 +404,6 @@ void mp_emit_bc_adjust_stack_size(emit_t *emit, mp_int_t delta) {
if (emit->stack_size > emit->scope->stack_size) { if (emit->stack_size > emit->scope->stack_size) {
emit->scope->stack_size = emit->stack_size; emit->scope->stack_size = emit->stack_size;
} }
emit->last_emit_was_return_value = false;
} }
void mp_emit_bc_set_source_line(emit_t *emit, mp_uint_t source_line) { void mp_emit_bc_set_source_line(emit_t *emit, mp_uint_t source_line) {
@ -773,7 +766,6 @@ void mp_emit_bc_call_method(emit_t *emit, mp_uint_t n_positional, mp_uint_t n_ke
void mp_emit_bc_return_value(emit_t *emit) { void mp_emit_bc_return_value(emit_t *emit) {
emit_write_bytecode_byte(emit, -1, MP_BC_RETURN_VALUE); emit_write_bytecode_byte(emit, -1, MP_BC_RETURN_VALUE);
emit->last_emit_was_return_value = true;
} }
void mp_emit_bc_raise_varargs(emit_t *emit, mp_uint_t n_args) { void mp_emit_bc_raise_varargs(emit_t *emit, mp_uint_t n_args) {
@ -806,7 +798,6 @@ const emit_method_table_t emit_bc_method_table = {
mp_emit_bc_start_pass, mp_emit_bc_start_pass,
mp_emit_bc_end_pass, mp_emit_bc_end_pass,
mp_emit_bc_last_emit_was_return_value,
mp_emit_bc_adjust_stack_size, mp_emit_bc_adjust_stack_size,
mp_emit_bc_set_source_line, mp_emit_bc_set_source_line,

15
py/emitnative.c
View File

@ -276,8 +276,6 @@ struct _emit_t {
uint16_t n_info; uint16_t n_info;
uint16_t n_cell; uint16_t n_cell;
bool last_emit_was_return_value;
scope_t *scope; scope_t *scope;
ASM_T *as; ASM_T *as;
@ -370,7 +368,6 @@ STATIC void emit_native_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scop
emit->pass = pass; emit->pass = pass;
emit->do_viper_types = scope->emit_options == MP_EMIT_OPT_VIPER; emit->do_viper_types = scope->emit_options == MP_EMIT_OPT_VIPER;
emit->stack_size = 0; emit->stack_size = 0;
emit->last_emit_was_return_value = false;
emit->scope = scope; emit->scope = scope;
// allocate memory for keeping track of the types of locals // allocate memory for keeping track of the types of locals
@ -733,10 +730,6 @@ STATIC bool emit_native_end_pass(emit_t *emit) {
return true; return true;
} }
STATIC bool emit_native_last_emit_was_return_value(emit_t *emit) {
return emit->last_emit_was_return_value;
}
STATIC void ensure_extra_stack(emit_t *emit, size_t delta) { STATIC void ensure_extra_stack(emit_t *emit, size_t delta) {
if (emit->stack_size + delta > emit->stack_info_alloc) { if (emit->stack_size + delta > emit->stack_info_alloc) {
size_t new_alloc = (emit->stack_size + delta + 8) & ~3; size_t new_alloc = (emit->stack_size + delta + 8) & ~3;
@ -793,7 +786,7 @@ STATIC void emit_native_set_source_line(emit_t *emit, mp_uint_t source_line) {
// this must be called at start of emit functions // this must be called at start of emit functions
STATIC void emit_native_pre(emit_t *emit) { STATIC void emit_native_pre(emit_t *emit) {
emit->last_emit_was_return_value = false; (void)emit;
} }
// depth==0 is top, depth==1 is before top, etc // depth==0 is top, depth==1 is before top, etc
@ -917,7 +910,6 @@ STATIC void emit_fold_stack_top(emit_t *emit, int reg_dest) {
// If stacked value is in a register and the register is not r1 or r2, then // If stacked value is in a register and the register is not r1 or r2, then
// *reg_dest is set to that register. Otherwise the value is put in *reg_dest. // *reg_dest is set to that register. Otherwise the value is put in *reg_dest.
STATIC void emit_pre_pop_reg_flexible(emit_t *emit, vtype_kind_t *vtype, int *reg_dest, int not_r1, int not_r2) { STATIC void emit_pre_pop_reg_flexible(emit_t *emit, vtype_kind_t *vtype, int *reg_dest, int not_r1, int not_r2) {
emit->last_emit_was_return_value = false;
stack_info_t *si = peek_stack(emit, 0); stack_info_t *si = peek_stack(emit, 0);
if (si->kind == STACK_REG && si->data.u_reg != not_r1 && si->data.u_reg != not_r2) { if (si->kind == STACK_REG && si->data.u_reg != not_r1 && si->data.u_reg != not_r2) {
*vtype = si->vtype; *vtype = si->vtype;
@ -930,12 +922,10 @@ STATIC void emit_pre_pop_reg_flexible(emit_t *emit, vtype_kind_t *vtype, int *re
} }
STATIC void emit_pre_pop_discard(emit_t *emit) { STATIC void emit_pre_pop_discard(emit_t *emit) {
emit->last_emit_was_return_value = false;
adjust_stack(emit, -1); adjust_stack(emit, -1);
} }
STATIC void emit_pre_pop_reg(emit_t *emit, vtype_kind_t *vtype, int reg_dest) { STATIC void emit_pre_pop_reg(emit_t *emit, vtype_kind_t *vtype, int reg_dest) {
emit->last_emit_was_return_value = false;
emit_access_stack(emit, 1, vtype, reg_dest); emit_access_stack(emit, 1, vtype, reg_dest);
adjust_stack(emit, -1); adjust_stack(emit, -1);
} }
@ -2771,7 +2761,6 @@ STATIC void emit_native_return_value(emit_t *emit) {
// Do the unwinding jump to get to the return handler // Do the unwinding jump to get to the return handler
emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size); emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size);
emit->last_emit_was_return_value = true;
return; return;
} }
@ -2809,7 +2798,6 @@ STATIC void emit_native_return_value(emit_t *emit) {
ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_RET_VAL(emit), REG_PARENT_RET); ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_RET_VAL(emit), REG_PARENT_RET);
} }
emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size); emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size);
emit->last_emit_was_return_value = true;
} }
STATIC void emit_native_raise_varargs(emit_t *emit, mp_uint_t n_args) { STATIC void emit_native_raise_varargs(emit_t *emit, mp_uint_t n_args) {
@ -2928,7 +2916,6 @@ const emit_method_table_t EXPORT_FUN(method_table) = {
emit_native_start_pass, emit_native_start_pass,
emit_native_end_pass, emit_native_end_pass,
emit_native_last_emit_was_return_value,
emit_native_adjust_stack_size, emit_native_adjust_stack_size,
emit_native_set_source_line, emit_native_set_source_line,

14
tests/cmdline/cmd_showbc.py.exp
View File

@ -48,12 +48,12 @@ arg names:
43 LOAD_CONST_NONE 43 LOAD_CONST_NONE
44 RETURN_VALUE 44 RETURN_VALUE
File cmdline/cmd_showbc.py, code block 'f' (descriptor: \.\+, bytecode @\.\+ 45\[46\] bytes) File cmdline/cmd_showbc.py, code block 'f' (descriptor: \.\+, bytecode @\.\+ 45\[46\] bytes)
Raw bytecode (code_info_size=8\[46\], bytecode_size=370): Raw bytecode (code_info_size=8\[46\], bytecode_size=372):
a8 12 9\[bf\] 03 05 60 60 26 22 24 64 22 24 25 25 24 a8 12 9\[bf\] 03 05 60 60 26 22 24 64 22 24 25 25 24
26 23 63 22 22 25 23 23 2f 6c 25 65 25 25 69 68 26 23 63 22 22 25 23 23 2f 6c 25 65 25 25 69 68
26 65 27 6a 62 20 23 62 2a 29 69 24 25 28 67 26 26 65 27 6a 62 20 23 62 2a 29 69 24 25 28 67 26
######## ########
\.\+81 63 \.\+51 63
arg names: arg names:
(N_STATE 22) (N_STATE 22)
(N_EXC_STACK 2) (N_EXC_STACK 2)
@ -403,6 +403,8 @@ arg names:
367 RETURN_VALUE 367 RETURN_VALUE
368 LOAD_CONST_SMALL_INT 1 368 LOAD_CONST_SMALL_INT 1
369 RETURN_VALUE 369 RETURN_VALUE
370 LOAD_CONST_NONE
371 RETURN_VALUE
File cmdline/cmd_showbc.py, code block 'f' (descriptor: \.\+, bytecode @\.\+ 59 bytes) File cmdline/cmd_showbc.py, code block 'f' (descriptor: \.\+, bytecode @\.\+ 59 bytes)
Raw bytecode (code_info_size=8, bytecode_size=51): Raw bytecode (code_info_size=8, bytecode_size=51):
a8 10 0a 05 80 82 34 38 81 57 c0 57 c1 57 c2 57 a8 10 0a 05 80 82 34 38 81 57 c0 57 c1 57 c2 57
@ -621,9 +623,9 @@ arg names: *
08 DELETE_DEREF 0 08 DELETE_DEREF 0
10 LOAD_CONST_NONE 10 LOAD_CONST_NONE
11 RETURN_VALUE 11 RETURN_VALUE
File cmdline/cmd_showbc.py, code block 'f' (descriptor: \.\+, bytecode @\.\+ 13 bytes) File cmdline/cmd_showbc.py, code block 'f' (descriptor: \.\+, bytecode @\.\+ 15 bytes)
Raw bytecode (code_info_size=8, bytecode_size=5): Raw bytecode (code_info_size=8, bytecode_size=7):
9a 01 0a 05 03 08 80 8b b1 25 00 f2 63 9a 01 0a 05 03 08 80 8b b1 25 00 f2 63 51 63
arg names: * b arg names: * b
(N_STATE 4) (N_STATE 4)
(N_EXC_STACK 0) (N_EXC_STACK 0)
@ -633,6 +635,8 @@ arg names: * b
01 LOAD_DEREF 0 01 LOAD_DEREF 0
03 BINARY_OP 27 __add__ 03 BINARY_OP 27 __add__
04 RETURN_VALUE 04 RETURN_VALUE
05 LOAD_CONST_NONE
06 RETURN_VALUE
mem: total=\\d\+, current=\\d\+, peak=\\d\+ mem: total=\\d\+, current=\\d\+, peak=\\d\+
stack: \\d\+ out of \\d\+ stack: \\d\+ out of \\d\+
GC: total: \\d\+, used: \\d\+, free: \\d\+ GC: total: \\d\+, used: \\d\+, free: \\d\+