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pythongh-87092: assembler uses instruction sequence instead of CFG
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@iritkatriel
iritkatriel committed Apr 27, 2023
1 parent d45225b commit a4b1924
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Showing 5 changed files with 83 additions and 72 deletions.
8 changes: 8 additions & 0 deletions Include/internal/pycore_compile.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,11 +33,17 @@ extern int _PyAST_Optimize(
struct _arena *arena,
_PyASTOptimizeState *state);

typedef struct {
int h_offset;
int h_startdepth;
int h_preserve_lasti;
} _PyCompilerExceptHandlerInfo;

typedef struct {
int i_opcode;
int i_oparg;
_PyCompilerSrcLocation i_loc;
_PyCompilerExceptHandlerInfo i_except_handler_info;
} _PyCompilerInstruction;

typedef struct {
Expand Down Expand Up @@ -82,6 +88,8 @@ int _PyCompile_EnsureArrayLargeEnough(

int _PyCompile_ConstCacheMergeOne(PyObject *const_cache, PyObject **obj);

int _PyCompile_InstrSize(int opcode, int oparg);

/* Access compiler internals for unit testing */

PyAPI_FUNC(PyObject*) _PyCompile_CodeGen(
Expand Down
3 changes: 1 addition & 2 deletions Include/internal/pycore_flowgraph.h
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Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,6 @@ int _PyCfg_OptimizeCodeUnit(_PyCfgBuilder *g, PyObject *consts, PyObject *const_
int _PyCfg_Stackdepth(_PyCfgBasicblock *entryblock, int code_flags);
void _PyCfg_ConvertExceptionHandlersToNops(_PyCfgBasicblock *entryblock);
int _PyCfg_ResolveJumps(_PyCfgBuilder *g);
int _PyCfg_InstrSize(_PyCfgInstruction *instruction);


static inline int
Expand All @@ -113,7 +112,7 @@ basicblock_nofallthrough(const _PyCfgBasicblock *b) {

PyCodeObject *
_PyAssemble_MakeCodeObject(_PyCompile_CodeUnitMetadata *u, PyObject *const_cache,
PyObject *consts, int maxdepth, _PyCfgBasicblock *entryblock,
PyObject *consts, int maxdepth, _PyCompile_InstructionSequence *instrs,
int nlocalsplus, int code_flags, PyObject *filename);

#ifdef __cplusplus
Expand Down
91 changes: 44 additions & 47 deletions Python/assemble.c
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Original file line number Diff line number Diff line change
Expand Up @@ -22,8 +22,8 @@
}

typedef _PyCompilerSrcLocation location;
typedef _PyCfgInstruction cfg_instr;
typedef _PyCfgBasicblock basicblock;
typedef _PyCompilerInstruction instruction;
typedef _PyCompile_InstructionSequence instr_sequence;

static inline bool
same_location(location a, location b)
Expand Down Expand Up @@ -117,21 +117,22 @@ assemble_emit_exception_table_item(struct assembler *a, int value, int msb)
#define MAX_SIZE_OF_ENTRY 20

static int
assemble_emit_exception_table_entry(struct assembler *a, int start, int end, basicblock *handler)
assemble_emit_exception_table_entry(struct assembler *a, int start, int end,
_PyCompilerExceptHandlerInfo *handler)
{
Py_ssize_t len = PyBytes_GET_SIZE(a->a_except_table);
if (a->a_except_table_off + MAX_SIZE_OF_ENTRY >= len) {
RETURN_IF_ERROR(_PyBytes_Resize(&a->a_except_table, len * 2));
}
int size = end-start;
assert(end > start);
int target = handler->b_offset;
int depth = handler->b_startdepth - 1;
if (handler->b_preserve_lasti) {
int target = handler->h_offset;
int depth = handler->h_startdepth - 1;
if (handler->h_preserve_lasti) {
depth -= 1;
}
assert(depth >= 0);
int depth_lasti = (depth<<1) | handler->b_preserve_lasti;
int depth_lasti = (depth<<1) | handler->h_preserve_lasti;
assemble_emit_exception_table_item(a, start, (1<<7));
assemble_emit_exception_table_item(a, size, 0);
assemble_emit_exception_table_item(a, target, 0);
Expand All @@ -140,29 +141,26 @@ assemble_emit_exception_table_entry(struct assembler *a, int start, int end, bas
}

static int
assemble_exception_table(struct assembler *a, basicblock *entryblock)
assemble_exception_table(struct assembler *a, instr_sequence *instrs)
{
basicblock *b;
int ioffset = 0;
basicblock *handler = NULL;
_PyCompilerExceptHandlerInfo handler;
handler.h_offset = -1;
int start = -1;
for (b = entryblock; b != NULL; b = b->b_next) {
ioffset = b->b_offset;
for (int i = 0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
if (instr->i_except != handler) {
if (handler != NULL) {
RETURN_IF_ERROR(
assemble_emit_exception_table_entry(a, start, ioffset, handler));
}
start = ioffset;
handler = instr->i_except;
for (int i = 0; i < instrs->s_used; i++) {
instruction *instr = &instrs->s_instrs[i];
if (instr->i_except_handler_info.h_offset != handler.h_offset) {
if (handler.h_offset >= 0) {
RETURN_IF_ERROR(
assemble_emit_exception_table_entry(a, start, ioffset, &handler));
}
ioffset += _PyCfg_InstrSize(instr);
start = ioffset;
handler = instr->i_except_handler_info;
}
ioffset += _PyCompile_InstrSize(instr->i_opcode, instr->i_oparg);
}
if (handler != NULL) {
RETURN_IF_ERROR(assemble_emit_exception_table_entry(a, start, ioffset, handler));
if (handler.h_offset >= 0) {
RETURN_IF_ERROR(assemble_emit_exception_table_entry(a, start, ioffset, &handler));
}
return SUCCESS;
}
Expand Down Expand Up @@ -316,31 +314,31 @@ assemble_emit_location(struct assembler* a, location loc, int isize)
}

static int
assemble_location_info(struct assembler *a, basicblock *entryblock, int firstlineno)
assemble_location_info(struct assembler *a, instr_sequence *instrs,
int firstlineno)
{
a->a_lineno = firstlineno;
location loc = NO_LOCATION;
int size = 0;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
for (int j = 0; j < b->b_iused; j++) {
if (!same_location(loc, b->b_instr[j].i_loc)) {
for (int i = 0; i < instrs->s_used; i++) {
instruction *instr = &instrs->s_instrs[i];
if (!same_location(loc, instr->i_loc)) {
RETURN_IF_ERROR(assemble_emit_location(a, loc, size));
loc = b->b_instr[j].i_loc;
loc = instr->i_loc;
size = 0;
}
size += _PyCfg_InstrSize(&b->b_instr[j]);
}
size += _PyCompile_InstrSize(instr->i_opcode, instr->i_oparg);
}
RETURN_IF_ERROR(assemble_emit_location(a, loc, size));
return SUCCESS;
}

static void
write_instr(_Py_CODEUNIT *codestr, cfg_instr *instruction, int ilen)
write_instr(_Py_CODEUNIT *codestr, instruction *instr, int ilen)
{
int opcode = instruction->i_opcode;
int opcode = instr->i_opcode;
assert(!IS_PSEUDO_OPCODE(opcode));
int oparg = instruction->i_oparg;
int oparg = instr->i_oparg;
assert(HAS_ARG(opcode) || oparg == 0);
int caches = _PyOpcode_Caches[opcode];
switch (ilen - caches) {
Expand Down Expand Up @@ -380,12 +378,12 @@ write_instr(_Py_CODEUNIT *codestr, cfg_instr *instruction, int ilen)
*/

static int
assemble_emit_instr(struct assembler *a, cfg_instr *i)
assemble_emit_instr(struct assembler *a, instruction *instr)
{
Py_ssize_t len = PyBytes_GET_SIZE(a->a_bytecode);
_Py_CODEUNIT *code;

int size = _PyCfg_InstrSize(i);
int size = _PyCompile_InstrSize(instr->i_opcode, instr->i_oparg);
if (a->a_offset + size >= len / (int)sizeof(_Py_CODEUNIT)) {
if (len > PY_SSIZE_T_MAX / 2) {
return ERROR;
Expand All @@ -394,25 +392,24 @@ assemble_emit_instr(struct assembler *a, cfg_instr *i)
}
code = (_Py_CODEUNIT *)PyBytes_AS_STRING(a->a_bytecode) + a->a_offset;
a->a_offset += size;
write_instr(code, i, size);
write_instr(code, instr, size);
return SUCCESS;
}

static int
assemble_emit(struct assembler *a, basicblock *entryblock, int first_lineno,
PyObject *const_cache)
assemble_emit(struct assembler *a, instr_sequence *instrs,
int first_lineno, PyObject *const_cache)
{
RETURN_IF_ERROR(assemble_init(a, first_lineno));

for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
for (int j = 0; j < b->b_iused; j++) {
RETURN_IF_ERROR(assemble_emit_instr(a, &b->b_instr[j]));
}
for (int i = 0; i < instrs->s_used; i++) {
instruction *instr = &instrs->s_instrs[i];
RETURN_IF_ERROR(assemble_emit_instr(a, instr));
}

RETURN_IF_ERROR(assemble_location_info(a, entryblock, a->a_lineno));
RETURN_IF_ERROR(assemble_location_info(a, instrs, a->a_lineno));

RETURN_IF_ERROR(assemble_exception_table(a, entryblock));
RETURN_IF_ERROR(assemble_exception_table(a, instrs));

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_except_table, a->a_except_table_off));
RETURN_IF_ERROR(_PyCompile_ConstCacheMergeOne(const_cache, &a->a_except_table));
Expand Down Expand Up @@ -586,13 +583,13 @@ makecode(_PyCompile_CodeUnitMetadata *umd, struct assembler *a, PyObject *const_

PyCodeObject *
_PyAssemble_MakeCodeObject(_PyCompile_CodeUnitMetadata *umd, PyObject *const_cache,
PyObject *consts, int maxdepth, basicblock *entryblock,
PyObject *consts, int maxdepth, instr_sequence *instrs,
int nlocalsplus, int code_flags, PyObject *filename)
{
PyCodeObject *co = NULL;

struct assembler a;
int res = assemble_emit(&a, entryblock, umd->u_firstlineno, const_cache);
int res = assemble_emit(&a, instrs, umd->u_firstlineno, const_cache);
if (res == SUCCESS) {
co = makecode(umd, &a, const_cache, consts, maxdepth, nlocalsplus,
code_flags, filename);
Expand Down
33 changes: 23 additions & 10 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -149,6 +149,17 @@ enum {
COMPILER_SCOPE_COMPREHENSION,
};


int
_PyCompile_InstrSize(int opcode, int oparg)
{
assert(!IS_PSEUDO_OPCODE(opcode));
assert(HAS_ARG(opcode) || oparg == 0);
int extended_args = (0xFFFFFF < oparg) + (0xFFFF < oparg) + (0xFF < oparg);
int caches = _PyOpcode_Caches[opcode];
return extended_args + 1 + caches;
}

typedef _PyCompilerInstruction instruction;
typedef _PyCompile_InstructionSequence instr_sequence;

Expand Down Expand Up @@ -6968,10 +6979,6 @@ optimize_and_assemble_code_unit(struct compiler_unit *u, PyObject *const_cache,
goto error;
}

if (cfg_to_instr_sequence(&g, &optimized_instrs) < 0) {
goto error;
}

/** Assembly **/
int nlocalsplus = prepare_localsplus(u, &g, code_flags);
if (nlocalsplus < 0) {
Expand All @@ -6994,11 +7001,10 @@ optimize_and_assemble_code_unit(struct compiler_unit *u, PyObject *const_cache,
goto error;
}


/* Can't modify the bytecode after computing jump offsets. */

co = _PyAssemble_MakeCodeObject(&u->u_metadata, const_cache, consts,
maxdepth, g.g_entryblock, nlocalsplus,
maxdepth, &optimized_instrs, nlocalsplus,
code_flags, filename);

error:
Expand Down Expand Up @@ -7039,11 +7045,18 @@ cfg_to_instr_sequence(cfg_builder *g, instr_sequence *seq)
RETURN_IF_ERROR(instr_sequence_use_label(seq, b->b_label.id));
for (int i = 0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
int arg = HAS_TARGET(instr->i_opcode) ?
instr->i_target->b_label.id :
instr->i_oparg;
RETURN_IF_ERROR(
instr_sequence_addop(seq, instr->i_opcode, arg, instr->i_loc));
instr_sequence_addop(seq, instr->i_opcode, instr->i_oparg, instr->i_loc));

_PyCompilerExceptHandlerInfo *hi = &seq->s_instrs[seq->s_used-1].i_except_handler_info;
if (instr->i_except != NULL) {
hi->h_offset = instr->i_except->b_offset;
hi->h_startdepth = instr->i_except->b_startdepth;
hi->h_preserve_lasti = instr->i_except->b_preserve_lasti;
}
else {
hi->h_offset = -1;
}
}
}
return SUCCESS;
Expand Down
20 changes: 7 additions & 13 deletions Python/flowgraph.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -166,24 +166,18 @@ _PyBasicblock_InsertInstruction(basicblock *block, int pos, cfg_instr *instr) {
return SUCCESS;
}

int
_PyCfg_InstrSize(cfg_instr *instruction)
static int
instr_size(cfg_instr *instruction)
{
int opcode = instruction->i_opcode;
assert(!IS_PSEUDO_OPCODE(opcode));
int oparg = instruction->i_oparg;
assert(HAS_ARG(opcode) || oparg == 0);
int extended_args = (0xFFFFFF < oparg) + (0xFFFF < oparg) + (0xFF < oparg);
int caches = _PyOpcode_Caches[opcode];
return extended_args + 1 + caches;
return _PyCompile_InstrSize(instruction->i_opcode, instruction->i_oparg);
}

static int
blocksize(basicblock *b)
{
int size = 0;
for (int i = 0; i < b->b_iused; i++) {
size += _PyCfg_InstrSize(&b->b_instr[i]);
size += instr_size(&b->b_instr[i]);
}
return size;
}
Expand Down Expand Up @@ -492,7 +486,7 @@ resolve_jump_offsets(basicblock *entryblock)
bsize = b->b_offset;
for (int i = 0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
int isize = _PyCfg_InstrSize(instr);
int isize = instr_size(instr);
/* jump offsets are computed relative to
* the instruction pointer after fetching
* the jump instruction.
Expand All @@ -508,7 +502,7 @@ resolve_jump_offsets(basicblock *entryblock)
assert(!IS_BACKWARDS_JUMP_OPCODE(instr->i_opcode));
instr->i_oparg -= bsize;
}
if (_PyCfg_InstrSize(instr) != isize) {
if (instr_size(instr) != isize) {
extended_arg_recompile = 1;
}
}
Expand All @@ -520,7 +514,7 @@ resolve_jump_offsets(basicblock *entryblock)
with a better solution.
The issue is that in the first loop blocksize() is called
which calls _PyCfg_InstrSize() which requires i_oparg be set
which calls instr_size() which requires i_oparg be set
appropriately. There is a bootstrap problem because
i_oparg is calculated in the second loop above.
Expand Down

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