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gh-104584: Baby steps towards generating and executing traces (#105924)
Added a new, experimental, tracing optimizer and interpreter (a.k.a. "tier 2"). This currently pessimizes, so don't use yet -- this is infrastructure so we can experiment with optimizing passes. To enable it, pass ``-Xuops`` or set ``PYTHONUOPS=1``. To get debug output, set ``PYTHONUOPSDEBUG=N`` where ``N`` is a debug level (0-4, where 0 is no debug output and 4 is excessively verbose). All of this code is likely to change dramatically before the 3.13 feature freeze. But this is a first step.
This commit is contained in:
Guido van Rossum
GitHub
parent
d3af83b934
commit
51fc725117
21 changed files with 2559 additions and 305 deletions
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@ -29,6 +29,9 @@ DEFAULT_METADATA_OUTPUT = os.path.relpath(
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DEFAULT_PYMETADATA_OUTPUT = os.path.relpath(
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os.path.join(ROOT, "Lib/_opcode_metadata.py")
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)
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DEFAULT_EXECUTOR_OUTPUT = os.path.relpath(
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os.path.join(ROOT, "Python/executor_cases.c.h")
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)
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BEGIN_MARKER = "// BEGIN BYTECODES //"
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END_MARKER = "// END BYTECODES //"
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RE_PREDICTED = (
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@ -61,6 +64,13 @@ arg_parser.add_argument(
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arg_parser.add_argument(
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"input", nargs=argparse.REMAINDER, help="Instruction definition file(s)"
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)
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arg_parser.add_argument(
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"-e",
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"--executor-cases",
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type=str,
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help="Write executor cases to this file",
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default=DEFAULT_EXECUTOR_OUTPUT,
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)
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def effect_size(effect: StackEffect) -> tuple[int, str]:
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@ -176,14 +186,14 @@ class Formatter:
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self.prefix = self.prefix[:-4]
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@contextlib.contextmanager
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def block(self, head: str):
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def block(self, head: str, tail: str = ""):
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if head:
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self.emit(head + " {")
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else:
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self.emit("{")
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with self.indent():
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yield
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self.emit("}")
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self.emit("}" + tail)
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def stack_adjust(
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self,
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@ -290,6 +300,29 @@ class InstructionFlags:
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f"(_PyOpcode_opcode_metadata[(OP)].flags & ({name}))")
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FORBIDDEN_NAMES_IN_UOPS = (
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"resume_with_error", # Proxy for "goto", which isn't an IDENTIFIER
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"unbound_local_error",
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"kwnames",
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"next_instr",
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"oparg1", # Proxy for super-instructions like LOAD_FAST_LOAD_FAST
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"JUMPBY",
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"DISPATCH",
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"INSTRUMENTED_JUMP",
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"throwflag",
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"exception_unwind",
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"import_from",
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"import_name",
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"_PyObject_CallNoArgs", # Proxy for BEFORE_WITH
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)
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# Interpreter tiers
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TIER_ONE = 1 # Specializing adaptive interpreter (PEP 659)
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TIER_TWO = 2 # Experimental tracing interpreter
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Tiers: typing.TypeAlias = typing.Literal[1, 2]
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@dataclasses.dataclass
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class Instruction:
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"""An instruction with additional data and code."""
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@ -353,7 +386,32 @@ class Instruction:
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cache = "0"
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self.instr_fmt = fmt
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def write(self, out: Formatter) -> None:
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def is_viable_uop(self) -> bool:
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"""Whether this instruction is viable as a uop."""
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if self.always_exits:
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return False
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if self.instr_flags.HAS_ARG_FLAG:
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# If the instruction uses oparg, it cannot use any caches
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for c in self.cache_effects:
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if c.name != UNUSED:
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return False
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else:
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# If it doesn't use oparg, it can have one cache entry
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caches: list[parser.CacheEffect] = []
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cache_offset = 0
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for c in self.cache_effects:
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if c.name != UNUSED:
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caches.append(c)
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cache_offset += c.size
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if len(caches) > 1:
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return False
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for forbidden in FORBIDDEN_NAMES_IN_UOPS:
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# TODO: Don't check in '#ifdef ENABLE_SPECIALIZATION' regions
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if variable_used(self.inst, forbidden):
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return False
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return True
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def write(self, out: Formatter, tier: Tiers = TIER_ONE) -> None:
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"""Write one instruction, sans prologue and epilogue."""
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# Write a static assertion that a family's cache size is correct
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if family := self.family:
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@ -400,7 +458,7 @@ class Instruction:
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# out.emit(f"next_instr += OPSIZE({self.inst.name}) - 1;")
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self.write_body(out, 0)
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self.write_body(out, 0, tier=tier)
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# Skip the rest if the block always exits
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if self.always_exits:
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@ -427,10 +485,16 @@ class Instruction:
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out.assign(dst, oeffect)
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# Write cache effect
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if self.cache_offset:
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if tier == TIER_ONE and self.cache_offset:
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out.emit(f"next_instr += {self.cache_offset};")
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def write_body(self, out: Formatter, dedent: int, cache_adjust: int = 0) -> None:
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def write_body(
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self,
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out: Formatter,
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dedent: int,
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cache_adjust: int = 0,
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tier: Tiers = TIER_ONE,
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) -> None:
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"""Write the instruction body."""
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# Write cache effect variable declarations and initializations
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cache_offset = cache_adjust
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@ -447,9 +511,12 @@ class Instruction:
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else:
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typ = f"uint{bits}_t "
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func = f"read_u{bits}"
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out.emit(
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f"{typ}{ceffect.name} = {func}(&next_instr[{cache_offset}].cache);"
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)
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if tier == TIER_ONE:
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out.emit(
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f"{typ}{ceffect.name} = {func}(&next_instr[{cache_offset}].cache);"
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)
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else:
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out.emit(f"{typ}{ceffect.name} = operand;")
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cache_offset += ceffect.size
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assert cache_offset == self.cache_offset + cache_adjust
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@ -573,16 +640,24 @@ class Analyzer:
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output_filename: str
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metadata_filename: str
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pymetadata_filename: str
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executor_filename: str
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errors: int = 0
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emit_line_directives: bool = False
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def __init__(self, input_filenames: list[str], output_filename: str,
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metadata_filename: str, pymetadata_filename: str):
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def __init__(
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self,
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input_filenames: list[str],
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output_filename: str,
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metadata_filename: str,
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pymetadata_filename: str,
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executor_filename: str,
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):
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"""Read the input file."""
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self.input_filenames = input_filenames
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self.output_filename = output_filename
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self.metadata_filename = metadata_filename
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self.pymetadata_filename = pymetadata_filename
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self.executor_filename = executor_filename
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def error(self, msg: str, node: parser.Node) -> None:
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lineno = 0
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@ -1107,6 +1182,8 @@ class Analyzer:
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self.write_pseudo_instrs()
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self.write_uop_defines()
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self.write_stack_effect_functions()
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# Write type definitions
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@ -1114,12 +1191,17 @@ class Analyzer:
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InstructionFlags.emit_macros(self.out)
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self.out.emit("struct opcode_metadata {")
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with self.out.indent():
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with self.out.block("struct opcode_metadata", ";"):
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self.out.emit("bool valid_entry;")
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self.out.emit("enum InstructionFormat instr_format;")
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self.out.emit("int flags;")
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self.out.emit("};")
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self.out.emit("")
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with self.out.block("struct opcode_macro_expansion", ";"):
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self.out.emit("int nuops;")
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self.out.emit("struct { int16_t uop; int8_t size; int8_t offset; } uops[8];")
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self.out.emit("")
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self.out.emit("")
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self.out.emit("#define OPCODE_METADATA_FMT(OP) "
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"(_PyOpcode_opcode_metadata[(OP)].instr_format)")
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@ -1130,7 +1212,9 @@ class Analyzer:
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# Write metadata array declaration
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self.out.emit("#ifndef NEED_OPCODE_METADATA")
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self.out.emit("extern const struct opcode_metadata _PyOpcode_opcode_metadata[512];")
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self.out.emit("extern const struct opcode_macro_expansion _PyOpcode_macro_expansion[256];")
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self.out.emit("#else")
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self.out.emit("const struct opcode_metadata _PyOpcode_opcode_metadata[512] = {")
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# Write metadata for each instruction
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@ -1150,6 +1234,31 @@ class Analyzer:
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# Write end of array
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self.out.emit("};")
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with self.out.block(
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"const struct opcode_macro_expansion _PyOpcode_macro_expansion[256] =",
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";",
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):
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# Write macro expansion for each non-pseudo instruction
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for thing in self.everything:
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match thing:
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case OverriddenInstructionPlaceHolder():
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pass
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case parser.InstDef(name=name):
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instr = self.instrs[name]
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if instr.kind != "op" and instr.is_viable_uop():
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self.out.emit(
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f"[{name}] = "
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f"{{ .nuops = 1, .uops = {{ {{ {name}, 0, 0 }} }} }},"
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)
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case parser.Macro():
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# TODO: emit expansion if all parts are viable uops
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pass
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case parser.Pseudo():
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pass
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case _:
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typing.assert_never(thing)
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self.out.emit("#endif")
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with open(self.pymetadata_filename, "w") as f:
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@ -1184,7 +1293,6 @@ class Analyzer:
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"opcode for family in _specializations.values() for opcode in family"
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"]")
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def write_pseudo_instrs(self) -> None:
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"""Write the IS_PSEUDO_INSTR macro"""
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self.out.emit("\n\n#define IS_PSEUDO_INSTR(OP) \\")
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@ -1192,6 +1300,20 @@ class Analyzer:
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self.out.emit(f" ((OP) == {op}) || \\")
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self.out.emit(f" 0")
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def write_uop_defines(self) -> None:
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"""Write '#define XXX NNN' for each uop"""
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self.out.emit("")
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counter = 300
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def add(name: str) -> None:
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nonlocal counter
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self.out.emit(f"#define {name} {counter}")
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counter += 1
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add("EXIT_TRACE")
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add("SET_IP")
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for instr in self.instrs.values():
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if instr.kind == "op" and instr.is_viable_uop():
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add(instr.name)
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def emit_metadata_entry(
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self, name: str, fmt: str, flags: InstructionFlags
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) -> None:
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@ -1221,10 +1343,7 @@ class Analyzer:
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# Create formatter
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self.out = Formatter(f, 8, self.emit_line_directives)
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# Write provenance header
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self.out.write_raw(f"{self.out.comment} This file is generated by {THIS}\n")
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self.out.write_raw(self.from_source_files())
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self.out.write_raw(f"{self.out.comment} Do not edit!\n")
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self.write_provenance_header()
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# Write and count instructions of all kinds
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n_instrs = 0
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@ -1252,6 +1371,33 @@ class Analyzer:
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file=sys.stderr,
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)
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def write_executor_instructions(self) -> None:
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"""Generate cases for the Tier 2 interpreter."""
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with open(self.executor_filename, "w") as f:
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self.out = Formatter(f, 8)
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self.write_provenance_header()
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for thing in self.everything:
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match thing:
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case OverriddenInstructionPlaceHolder():
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self.write_overridden_instr_place_holder(thing)
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case parser.InstDef():
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instr = self.instrs[thing.name]
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if instr.is_viable_uop():
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self.out.emit("")
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with self.out.block(f"case {thing.name}:"):
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instr.write(self.out, tier=TIER_TWO)
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self.out.emit("break;")
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case parser.Macro():
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pass # TODO
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case parser.Pseudo():
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pass
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case _:
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typing.assert_never(thing)
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print(
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f"Wrote some stuff to {self.executor_filename}",
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file=sys.stderr,
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)
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def write_overridden_instr_place_holder(self,
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place_holder: OverriddenInstructionPlaceHolder) -> None:
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self.out.emit("")
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@ -1405,7 +1551,7 @@ def main():
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args.input.append(DEFAULT_INPUT)
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# Raises OSError if input unreadable
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a = Analyzer(args.input, args.output, args.metadata, args.pymetadata)
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a = Analyzer(args.input, args.output, args.metadata, args.pymetadata, args.executor_cases)
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if args.emit_line_directives:
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a.emit_line_directives = True
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@ -1415,6 +1561,7 @@ def main():
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sys.exit(f"Found {a.errors} errors")
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a.write_instructions() # Raises OSError if output can't be written
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a.write_metadata()
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a.write_executor_instructions()
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if __name__ == "__main__":
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