WIP: start on spilling

Author: msullivan

mypyc/analysis/dataflow.py

@@ -17,6 +17,7 @@
     Cast,
     ComparisonOp,
     ControlOp,
+    DecRef,
     Extend,
     Float,
     FloatComparisonOp,
@@ -25,6 +26,7 @@
     GetAttr,
     GetElementPtr,
     Goto,
+    IncRef,
     InitStatic,
     Integer,
     IntOp,
@@ -79,12 +81,11 @@ def __str__(self) -> str:
         return "\n".join(lines)
 
 
-def get_cfg(blocks: list[BasicBlock]) -> CFG:
+def get_cfg(blocks: list[BasicBlock], *, use_yields: bool = False) -> CFG:
     """Calculate basic block control-flow graph.
 
-    The result is a dictionary like this:
-
-         basic block index -> (successors blocks, predecesssor blocks)
+    If use_yields is set, then we treat returns inserted by yields as gotos
+    instead of exits.
     """
     succ_map = {}
     pred_map: dict[BasicBlock, list[BasicBlock]] = {}
@@ -94,7 +95,10 @@ def get_cfg(blocks: list[BasicBlock]) -> CFG:
             isinstance(op, ControlOp) for op in block.ops[:-1]
         ), "Control-flow ops must be at the end of blocks"
 
-        succ = list(block.terminator.targets())
+        if use_yields and isinstance(block.terminator, Return) and block.terminator.yield_target:
+            succ = [block.terminator.yield_target]
+        else:
+            succ = list(block.terminator.targets())
         if not succ:
             exits.add(block)
 
@@ -494,6 +498,12 @@ def visit_assign_multi(self, op: AssignMulti) -> GenAndKill[Value]:
     def visit_set_mem(self, op: SetMem) -> GenAndKill[Value]:
         return non_trivial_sources(op), set()
 
+    def visit_inc_ref(self, op: IncRef) -> GenAndKill[Value]:
+        return set(), set()
+
+    def visit_dec_ref(self, op: DecRef) -> GenAndKill[Value]:
+        return set(), set()
+
 
 def analyze_live_regs(blocks: list[BasicBlock], cfg: CFG) -> AnalysisResult[Value]:
     """Calculate live registers at each CFG location.

mypyc/codegen/emitmodule.py

@@ -58,6 +58,7 @@
 from mypyc.options import CompilerOptions
 from mypyc.transform.exceptions import insert_exception_handling
 from mypyc.transform.refcount import insert_ref_count_opcodes
+from mypyc.transform.spill import insert_spills
 from mypyc.transform.uninit import insert_uninit_checks
 
 # All of the modules being compiled are divided into "groups". A group
@@ -225,6 +226,10 @@ def compile_scc_to_ir(
     if errors.num_errors > 0:
         return modules
 
+    # XXX: HOW WILL WE DEAL WITH REFCOUNTING ON THE SPILLAGE
+    # DO WE DO IT... LAST? MAYBE MAYBE MAYBE YES
+    # ONLY DO UNINIT.... YEAH OK
+
     # Insert uninit checks.
     for module in modules.values():
         for fn in module.functions:
@@ -237,6 +242,10 @@ def compile_scc_to_ir(
     for module in modules.values():
         for fn in module.functions:
             insert_ref_count_opcodes(fn)
+    for module in modules.values():
+        for cls in module.classes:
+            if cls.env_user_function:
+                insert_spills(cls.env_user_function, cls)
 
     return modules
 

mypyc/ir/class_ir.py

@@ -194,6 +194,9 @@ def __init__(
         # value of an attribute is the same as the error value.
         self.bitmap_attrs: list[str] = []
 
+        # If this is a generator environment class, what is the actual method for it
+        self.env_user_function: FuncIR | None = None
+
     def __repr__(self) -> str:
         return (
             "ClassIR("
@@ -391,6 +394,7 @@ def serialize(self) -> JsonDict:
             "_always_initialized_attrs": sorted(self._always_initialized_attrs),
             "_sometimes_initialized_attrs": sorted(self._sometimes_initialized_attrs),
             "init_self_leak": self.init_self_leak,
+            "env_user_function": self.env_user_function.id if self.env_user_function else None,
         }
 
     @classmethod
@@ -442,6 +446,9 @@ def deserialize(cls, data: JsonDict, ctx: DeserMaps) -> ClassIR:
         ir._always_initialized_attrs = set(data["_always_initialized_attrs"])
         ir._sometimes_initialized_attrs = set(data["_sometimes_initialized_attrs"])
         ir.init_self_leak = data["init_self_leak"]
+        ir.env_user_function = (
+            ctx.functions[data["env_user_function"]] if data["env_user_function"] else None
+        )
 
         return ir
 

mypyc/ir/ops.py

@@ -430,9 +430,16 @@ class Return(ControlOp):
 
     error_kind = ERR_NEVER
 
-    def __init__(self, value: Value, line: int = -1) -> None:
+    def __init__(
+        self, value: Value, line: int = -1, *, yield_target: BasicBlock | None = None
+    ) -> None:
         super().__init__(line)
         self.value = value
+        # If this return is created by a yield, keep track of the next
+        # basic block. This doesn't affect the code we generate but
+        # can feed into analysis that need to understand the
+        # *original* CFG.
+        self.yield_target = yield_target
 
     def sources(self) -> list[Value]:
         return [self.value]

mypyc/irbuild/function.py

@@ -269,6 +269,7 @@ def c() -> None:
         # Re-enter the FuncItem and visit the body of the function this time.
         builder.enter(fn_info)
         setup_env_for_generator_class(builder)
+
         load_outer_envs(builder, builder.fn_info.generator_class)
         top_level = builder.top_level_fn_info()
         if (

mypyc/irbuild/generator.py

@@ -181,6 +181,8 @@ def add_helper_to_generator_class(
     )
     fn_info.generator_class.ir.methods["__mypyc_generator_helper__"] = helper_fn_ir
     builder.functions.append(helper_fn_ir)
+    fn_info.env_class.env_user_function = helper_fn_ir
+
     return helper_fn_decl
 
 

mypyc/irbuild/statement.py

@@ -894,7 +894,7 @@ def emit_yield(builder: IRBuilder, val: Value, line: int) -> Value:
     next_label = len(cls.continuation_blocks)
     cls.continuation_blocks.append(next_block)
     builder.assign(cls.next_label_target, Integer(next_label), line)
-    builder.add(Return(retval))
+    builder.add(Return(retval, yield_target=next_block))
     builder.activate_block(next_block)
 
     add_raise_exception_blocks_to_generator_class(builder, line)

mypyc/test-data/run-generators.test

@@ -679,3 +679,21 @@ def test_basic() -> None:
     with context:
         assert context.x == 1
     assert context.x == 0
+
+
+[case testYieldSpill]
+from typing import Generator
+
+def f() -> int:
+    return 1
+
+def yield_spill() -> Generator[str, int, int]:
+    return f() + (yield "foo")
+
+[file driver.py]
+from native import yield_spill
+from testutil import run_generator
+
+yields, val = run_generator(yield_spill(), [2])
+assert yields == ('foo',)
+assert val == 3, val

mypyc/transform/spill.py

@@ -0,0 +1,108 @@
+"""Insert spills for values that are live across yields."""
+
+from __future__ import annotations
+
+from mypyc.analysis.dataflow import AnalysisResult, analyze_live_regs, get_cfg
+from mypyc.common import TEMP_ATTR_NAME
+from mypyc.ir.class_ir import ClassIR
+from mypyc.ir.func_ir import FuncIR
+from mypyc.ir.ops import (
+    BasicBlock,
+    Branch,
+    DecRef,
+    GetAttr,
+    IncRef,
+    LoadErrorValue,
+    Register,
+    SetAttr,
+    Value,
+)
+
+
+def insert_spills(ir: FuncIR, env: ClassIR) -> None:
+    cfg = get_cfg(ir.blocks, use_yields=True)
+    live = analyze_live_regs(ir.blocks, cfg)
+    entry_live = live.before[ir.blocks[0], 0]
+
+    # from mypyc.ir.pprint import format_func
+
+    # print('\n'.join(format_func(ir)))
+
+    entry_live = {op for op in entry_live if not (isinstance(op, Register) and op.is_arg)}
+    # XXX: Actually for now, no Registers at all -- we keep the manual spills
+    entry_live = {op for op in entry_live if not isinstance(op, Register)}
+
+    ir.blocks = spill_regs(ir.blocks, env, entry_live, live)
+    # print("\n".join(format_func(ir)))
+    # print("\n\n\n=========")
+
+
+def spill_regs(
+    blocks: list[BasicBlock], env: ClassIR, to_spill: set[Value], live: AnalysisResult[Value]
+) -> list[BasicBlock]:
+    for op in blocks[0].ops:
+        if isinstance(op, GetAttr) and op.attr == "__mypyc_env__":
+            env_reg = op
+            break
+    else:
+        raise AssertionError("could not find __mypyc_env__")
+
+    spill_locs = {}
+    for i, val in enumerate(to_spill):
+        name = f"{TEMP_ATTR_NAME}2_{i}"
+        env.attributes[name] = val.type
+        spill_locs[val] = name
+
+    for block in blocks:
+        ops = block.ops
+        block.ops = []
+
+        for i, op in enumerate(ops):
+            to_decref = []
+
+            if isinstance(op, IncRef) and op.src in spill_locs:
+                raise AssertionError("not sure what to do with an incref of a spill...")
+            if isinstance(op, DecRef) and op.src in spill_locs:
+                # When we decref a spilled value, we turn that into
+                # NULLing out the attribute, but only if the spilled
+                # value is not live *when we include yields in the
+                # CFG*. (The original decrefs are computed without that.)
+                #
+                # We also skip a decref is the env register is not
+                # live. That should only happen when an exception is
+                # being raised, so everything should be handled there.
+                if op.src not in live.after[block, i] and env_reg in live.after[block, i]:
+                    # Skip the DecRef but null out the spilled location
+                    null = LoadErrorValue(op.src.type)
+                    block.ops.extend([null, SetAttr(env_reg, spill_locs[op.src], null, op.line)])
+                continue
+
+            if (
+                any(src in spill_locs for src in op.sources())
+                # N.B: IS_ERROR should be before a spill happens
+                # XXX: but could we have a regular branch?
+                and not (isinstance(op, Branch) and op.op == Branch.IS_ERROR)
+            ):
+                new_sources: list[Value] = []
+                for src in op.sources():
+                    if src in spill_locs:
+                        read = GetAttr(env_reg, spill_locs[src], op.line)
+                        block.ops.append(read)
+                        new_sources.append(read)
+                        if src.type.is_refcounted:
+                            to_decref.append(read)
+                    else:
+                        new_sources.append(src)
+
+                op.set_sources(new_sources)
+
+            block.ops.append(op)
+
+            for dec in to_decref:
+                block.ops.append(DecRef(dec))
+
+            if op in spill_locs:
+                # XXX: could we set uninit?
+                block.ops.append(SetAttr(env_reg, spill_locs[op], op, op.line))
+
+    return blocks