pythongh-119689: generate stack effect metadata for pseudo instructions

Lib/test/test_generated_cases.py

@@ -485,7 +485,7 @@ def test_unused_caches(self):
 
     def test_pseudo_instruction_no_flags(self):
         input = """
-        pseudo(OP) = {
+        pseudo(OP, (in -- out1, out2)) = {
             OP1,
         };
 
@@ -504,7 +504,7 @@ def test_pseudo_instruction_no_flags(self):
 
     def test_pseudo_instruction_with_flags(self):
         input = """
-        pseudo(OP, (HAS_ARG, HAS_JUMP)) = {
+        pseudo(OP, (in1, in2 --), (HAS_ARG, HAS_JUMP)) = {
             OP1,
         };
 

Python/bytecodes.c

@@ -213,7 +213,7 @@ dummy_func(
             }
         }
 
-        pseudo(LOAD_CLOSURE) = {
+        pseudo(LOAD_CLOSURE, (-- unused)) = {
             LOAD_FAST,
         };
 
@@ -259,7 +259,7 @@ dummy_func(
             SETLOCAL(oparg, value);
         }
 
-        pseudo(STORE_FAST_MAYBE_NULL) = {
+        pseudo(STORE_FAST_MAYBE_NULL, (unused --)) = {
             STORE_FAST,
         };
 
@@ -2391,12 +2391,12 @@ dummy_func(
             #endif /* _Py_TIER2 */
         }
 
-        pseudo(JUMP) = {
+        pseudo(JUMP, (--)) = {
             JUMP_FORWARD,
             JUMP_BACKWARD,
         };
 
-        pseudo(JUMP_NO_INTERRUPT) = {
+        pseudo(JUMP_NO_INTERRUPT, (--)) = {
             JUMP_FORWARD,
             JUMP_BACKWARD_NO_INTERRUPT,
         };
@@ -2893,19 +2893,27 @@ dummy_func(
             ERROR_IF(res == NULL, error);
         }
 
-        pseudo(SETUP_FINALLY, (HAS_ARG)) = {
+        pseudo(SETUP_FINALLY, (-- unused), (HAS_ARG)) = {
+            /* If an exception is raised, restore the stack position
+             * and push one value before jumping to the handler.
+             */
             NOP,
         };
 
-        pseudo(SETUP_CLEANUP, (HAS_ARG)) = {
+        pseudo(SETUP_CLEANUP, (-- unused, unused), (HAS_ARG)) = {
+            /* As SETUP_FINALLY, but push lasti as well */
             NOP,
         };
 
-        pseudo(SETUP_WITH, (HAS_ARG)) = {
+        pseudo(SETUP_WITH, (-- unused), (HAS_ARG)) = {
+            /* If an exception is raised, restore the stack position to the
+             * position before the result of __(a)enter__ and push 2 values
+             * before jumping to the handler.
+             */
             NOP,
         };
 
-        pseudo(POP_BLOCK) = {
+        pseudo(POP_BLOCK, (--)) = {
             NOP,
         };
 

Python/compile.c

@@ -703,51 +703,22 @@ compiler_set_qualname(struct compiler *c)
 static int
 stack_effect(int opcode, int oparg, int jump)
 {
-    if (0 <= opcode && opcode <= MAX_REAL_OPCODE) {
-        if (_PyOpcode_Deopt[opcode] != opcode) {
-            // Specialized instructions are not supported.
-            return PY_INVALID_STACK_EFFECT;
-        }
-        int popped = _PyOpcode_num_popped(opcode, oparg);
-        int pushed = _PyOpcode_num_pushed(opcode, oparg);
-        if (popped < 0 || pushed < 0) {
-            return PY_INVALID_STACK_EFFECT;
-        }
-        return pushed - popped;
+    if (opcode < 0) {
+        return PY_INVALID_STACK_EFFECT;
     }
-
-    // Pseudo ops
-    switch (opcode) {
-        case POP_BLOCK:
-        case JUMP:
-        case JUMP_NO_INTERRUPT:
-            return 0;
-
-        /* Exception handling pseudo-instructions */
-        case SETUP_FINALLY:
-            /* 0 in the normal flow.
-             * Restore the stack position and push 1 value before jumping to
-             * the handler if an exception be raised. */
-            return jump ? 1 : 0;
-        case SETUP_CLEANUP:
-            /* As SETUP_FINALLY, but pushes lasti as well */
-            return jump ? 2 : 0;
-        case SETUP_WITH:
-            /* 0 in the normal flow.
-             * Restore the stack position to the position before the result
-             * of __(a)enter__ and push 2 values before jumping to the handler
-             * if an exception be raised. */
-            return jump ? 1 : 0;
-
-        case STORE_FAST_MAYBE_NULL:
-            return -1;
-        case LOAD_CLOSURE:
-            return 1;
-        default:
-            return PY_INVALID_STACK_EFFECT;
+    if ((opcode <= MAX_REAL_OPCODE) && (_PyOpcode_Deopt[opcode] != opcode)) {
+        // Specialized instructions are not supported.
+        return PY_INVALID_STACK_EFFECT;
     }
-
-    return PY_INVALID_STACK_EFFECT; /* not reachable */
+    int popped = _PyOpcode_num_popped(opcode, oparg);
+    int pushed = _PyOpcode_num_pushed(opcode, oparg);
+    if (popped < 0 || pushed < 0) {
+        return PY_INVALID_STACK_EFFECT;
+    }
+    if (IS_BLOCK_PUSH_OPCODE(opcode) && !jump) {
+        return 0;
+    }
+    return pushed - popped;
 }
 
 int

Tools/cases_generator/analyzer.py

@@ -235,6 +235,7 @@ def is_super(self) -> bool:
 @dataclass
 class PseudoInstruction:
     name: str
+    stack: StackEffect
     targets: list[Instruction]
     flags: list[str]
     opcode: int = -1
@@ -295,7 +296,7 @@ def convert_stack_item(item: parser.StackEffect, replace_op_arg_1: str | None) -
         item.name, item.type, cond, (item.size or "1")
     )
 
-def analyze_stack(op: parser.InstDef, replace_op_arg_1: str | None = None) -> StackEffect:
+def analyze_stack(op: parser.InstDef | parser.Pseudo, replace_op_arg_1: str | None = None) -> StackEffect:
     inputs: list[StackItem] = [
         convert_stack_item(i, replace_op_arg_1) for i in op.inputs if isinstance(i, parser.StackEffect)
     ]
@@ -706,6 +707,7 @@ def add_pseudo(
 ) -> None:
     pseudos[pseudo.name] = PseudoInstruction(
         pseudo.name,
+        analyze_stack(pseudo),
         [instructions[target] for target in pseudo.targets],
         pseudo.flags,
     )

Tools/cases_generator/opcode_metadata_generator.py

@@ -4,6 +4,7 @@
 """
 
 import argparse
+import itertools
 import os.path
 import sys
 
@@ -94,7 +95,8 @@ def emit_stack_effect_function(
 def generate_stack_effect_functions(analysis: Analysis, out: CWriter) -> None:
     popped_data: list[tuple[str, str]] = []
     pushed_data: list[tuple[str, str]] = []
-    for inst in analysis.instructions.values():
+    for inst in itertools.chain(analysis.instructions.values(),
+                                analysis.pseudos.values()):
         stack = get_stack_effect(inst)
         popped = (-stack.base_offset).to_c()
         pushed = (stack.top_offset - stack.base_offset).to_c()

Tools/cases_generator/parsing.py

@@ -138,6 +138,8 @@ class Family(Node):
 @dataclass
 class Pseudo(Node):
     name: str
+    inputs: list[InputEffect]
+    outputs: list[OutputEffect]
     flags: list[str]  # instr flags to set on the pseudo instruction
     targets: list[str]  # opcodes this can be replaced by
 
@@ -409,16 +411,18 @@ def pseudo_def(self) -> Pseudo | None:
             if self.expect(lx.LPAREN):
                 if tkn := self.expect(lx.IDENTIFIER):
                     if self.expect(lx.COMMA):
-                        flags = self.flags()
-                    else:
-                        flags = []
-                    if self.expect(lx.RPAREN):
-                        if self.expect(lx.EQUALS):
-                            if not self.expect(lx.LBRACE):
-                                raise self.make_syntax_error("Expected {")
-                            if members := self.members():
-                                if self.expect(lx.RBRACE) and self.expect(lx.SEMI):
-                                    return Pseudo(tkn.text, flags, members)
+                        inp, outp = self.io_effect()
+                        if self.expect(lx.COMMA):
+                            flags = self.flags()
+                        else:
+                            flags = []
+                        if self.expect(lx.RPAREN):
+                            if self.expect(lx.EQUALS):
+                                if not self.expect(lx.LBRACE):
+                                    raise self.make_syntax_error("Expected {")
+                                if members := self.members():
+                                    if self.expect(lx.RBRACE) and self.expect(lx.SEMI):
+                                        return Pseudo(tkn.text, inp, outp, flags, members)
         return None
 
     def members(self) -> list[str] | None:

Tools/cases_generator/stack.py

@@ -1,5 +1,5 @@
 import re
-from analyzer import StackItem, Instruction, Uop
+from analyzer import StackItem, Instruction, Uop, PseudoInstruction
 from dataclasses import dataclass
 from cwriter import CWriter
 
@@ -208,13 +208,20 @@ def as_comment(self) -> str:
         return f"/* Variables: {[v.name for v in self.variables]}. Base offset: {self.base_offset.to_c()}. Top offset: {self.top_offset.to_c()} */"
 
 
-def get_stack_effect(inst: Instruction) -> Stack:
+def get_stack_effect(inst: Instruction | PseudoInstruction) -> Stack:
     stack = Stack()
-    for uop in inst.parts:
-        if not isinstance(uop, Uop):
-            continue
-        for var in reversed(uop.stack.inputs):
+    def stacks(inst):
+        if isinstance(inst, Instruction):
+            for uop in inst.parts:
+                if isinstance(uop, Uop):
+                    yield uop.stack
+        else:
+            assert isinstance(inst, PseudoInstruction)
+            yield inst.stack
+
+    for s in stacks(inst):
+        for var in reversed(s.inputs):
             stack.pop(var)
-        for i, var in enumerate(uop.stack.outputs):
+        for var in s.outputs:
             stack.push(var)
     return stack