GH-117062: Make _JUMP_TO_TOP a general absolute jump (GH-120854)

Author: brandtbucher

Python/bytecodes.c

@@ -4149,9 +4149,7 @@ dummy_func(
         }
 
         op(_JUMP_TO_TOP, (--)) {
-#ifndef _Py_JIT
-            next_uop = &current_executor->trace[1];
-#endif
+            JUMP_TO_JUMP_TARGET();
         }
 
         tier2 op(_SET_IP, (instr_ptr/4 --)) {

Python/executor_cases.c.h

@@ -1059,6 +1059,11 @@ prepare_for_execution(_PyUOpInstruction *buffer, int length)
                 buffer[i].jump_target = 0;
             }
         }
+        if (opcode == _JUMP_TO_TOP) {
+            assert(buffer[0].opcode == _START_EXECUTOR);
+            buffer[i].format = UOP_FORMAT_JUMP;
+            buffer[i].jump_target = 1;
+        }
     }
     return next_spare;
 }

Python/optimizer.c

@@ -42,8 +42,6 @@ class HoleValue(enum.Enum):
     ERROR_TARGET = enum.auto()
     # The index of the exit to be jumped through (exposed as _JIT_EXIT_INDEX):
     EXIT_INDEX = enum.auto()
-    # The base address of the machine code for the first uop (exposed as _JIT_TOP):
-    TOP = enum.auto()
     # A hardcoded value of zero (used for symbol lookups):
     ZERO = enum.auto()
 
@@ -110,7 +108,6 @@ class HoleValue(enum.Enum):
     HoleValue.JUMP_TARGET: "instruction_starts[instruction->jump_target]",
     HoleValue.ERROR_TARGET: "instruction_starts[instruction->error_target]",
     HoleValue.EXIT_INDEX: "instruction->exit_index",
-    HoleValue.TOP: "instruction_starts[1]",
     HoleValue.ZERO: "",
 }
 

Tools/jit/_stencils.py

@@ -105,9 +105,6 @@ _JIT_ENTRY(_PyInterpreterFrame *frame, PyObject **stack_pointer, PyThreadState *
     UOP_STAT_INC(uopcode, execution_count);
 
     // The actual instruction definitions (only one will be used):
-    if (uopcode == _JUMP_TO_TOP) {
-        PATCH_JUMP(_JIT_TOP);
-    }
     switch (uopcode) {
 #include "executor_cases.c.h"
         default: