Modernize FORMAT_VALUE

Author: gvanrossum

Python/bytecodes.c

@@ -3052,18 +3052,10 @@ dummy_func(
             ERROR_IF(slice == NULL, error);
         }
 
-        // error: FORMAT_VALUE has irregular stack effect
-        inst(FORMAT_VALUE) {
+        inst(FORMAT_VALUE, (value, fmt_spec if ((oparg & FVS_MASK) == FVS_HAVE_SPEC) -- result)) {
             /* Handles f-string value formatting. */
-            PyObject *result;
-            PyObject *fmt_spec;
-            PyObject *value;
             PyObject *(*conv_fn)(PyObject *);
             int which_conversion = oparg & FVC_MASK;
-            int have_fmt_spec = (oparg & FVS_MASK) == FVS_HAVE_SPEC;
-
-            fmt_spec = have_fmt_spec ? POP() : NULL;
-            value = POP();
 
             /* See if any conversion is specified. */
             switch (which_conversion) {
@@ -3104,12 +3096,8 @@ dummy_func(
                 result = PyObject_Format(value, fmt_spec);
                 Py_DECREF(value);
                 Py_XDECREF(fmt_spec);
-                if (result == NULL) {
-                    goto error;
-                }
+                ERROR_IF(result == NULL, error);
             }
-
-            PUSH(result);
         }
 
         inst(COPY, (bottom, unused[oparg-1] -- bottom, unused[oparg-1], top)) {

Python/generated_cases.c.h

@@ -331,7 +331,7 @@ _PyOpcode_num_popped(int opcode, int oparg, bool jump) {
         case BUILD_SLICE:
             return ((oparg == 3) ? 1 : 0) + 2;
         case FORMAT_VALUE:
-            return -1;
+            return (((oparg & FVS_MASK) == FVS_HAVE_SPEC) ? 1 : 0) + 1;
         case COPY:
             return (oparg-1) + 1;
         case BINARY_OP:
@@ -677,7 +677,7 @@ _PyOpcode_num_pushed(int opcode, int oparg, bool jump) {
         case BUILD_SLICE:
             return 1;
         case FORMAT_VALUE:
-            return -1;
+            return 1;
         case COPY:
             return (oparg-1) + 2;
         case BINARY_OP: