Fix bug in predecessor detection

Tools/jit/_optimizers.py

@@ -131,15 +131,21 @@ def _blocks(self) -> typing.Generator[_Block, None, None]:
 
     def _body(self) -> str:
         lines = []
+        hot = True
         for block in self._blocks():
+            if hot != block.hot:
+                hot = block.hot
+                lines.append(f"# JIT: {'HOT' if hot else 'COLD'} ".ljust(80, "#"))
             lines.extend(block.noise)
             lines.extend(block.instructions)
         return "\n".join(lines)
 
     def _predecessors(self, block: _Block) -> typing.Generator[_Block, None, None]:
-        for block in self._blocks():
-            if block.target is block or (block.fallthrough and block.link is block):
-                yield block
+        for predecessor in self._blocks():
+            if predecessor.target is block or (
+                predecessor.fallthrough and predecessor.link is block
+            ):
+                yield predecessor
 
     def _insert_continue_label(self) -> None:
         for end in reversed(list(self._blocks())):
@@ -153,7 +159,7 @@ def _insert_continue_label(self) -> None:
         end.link, align.link, continuation.link = align, continuation, end.link
 
     def _mark_hot_blocks(self) -> None:
-        todo = [self._lookup_label(f"{self.prefix}_JIT_CONTINUE")]
+        todo = list(self._blocks())[-1:]
         while todo:
             block = todo.pop()
             block.hot = True
@@ -227,7 +233,6 @@ class OptimizerAArch64(Optimizer):
 
 
 class OptimizerX86(Optimizer):
-
     _branches = _X86_BRANCHES
     _re_branch = re.compile(
         rf"\s*(?P<instruction>{'|'.join(_X86_BRANCHES)})\s+(?P<target>[\w.]+)"
@@ -237,7 +242,6 @@ class OptimizerX86(Optimizer):
 
 
 class OptimizerX86Windows(OptimizerX86):
-
     def _preprocess(self, text: str) -> str:
         text = super()._preprocess(text)
         # rex64 jumpq *__imp__JIT_CONTINUE(%rip) -> jmp _JIT_CONTINUE

Tools/jit/_targets.py

@@ -136,7 +136,6 @@ async def _compile(
             f"-I{CPYTHON / 'Tools' / 'jit'}",
             "-O3",
             "-S",
-            # "-c",
             # Shorten full absolute file paths in the generated code (like the
             # __FILE__ macro and assert failure messages) for reproducibility:
             f"-ffile-prefix-map={CPYTHON}=.",
@@ -161,13 +160,7 @@ async def _compile(
         ]
         await _llvm.run("clang", args_s, echo=self.verbose)
         self.optimizer(s, prefix=self.prefix).run()
-        args_o = [
-            f"--target={self.triple}",
-            "-c",
-            "-o",
-            f"{o}",
-            f"{s}",
-        ]
+        args_o = [f"--target={self.triple}", "-c", "-o", f"{o}", f"{s}"]
         await _llvm.run("clang", args_o, echo=self.verbose)
         return await self._parse(o)