bpo-40941: Unify implicit and explicit state in the frame and generator objects into a single value. (GH-20803)

* Merge gen and frame state variables into one.

* Replace stack pointer with depth in PyFrameObject. Makes code easier to read and saves a word of memory.

1 files changed, 28 insertions, 5 deletions

diff --git a/Include/cpython/frameobject.h b/Include/cpython/frameobject.h
index c76fbe0..63240b5 100644
--- a/Include/cpython/frameobject.h
+++ b/Include/cpython/frameobject.h
@@ -4,6 +4,21 @@
 #  error "this header file must not be included directly"
 #endif
 
+/* These values are chosen so that the inline functions below all
+ * compare f_state to zero.
+ */
+enum _framestate {
+    FRAME_CREATED = -2,
+    FRAME_SUSPENDED = -1,
+    FRAME_EXECUTING = 0,
+    FRAME_RETURNED = 1,
+    FRAME_UNWINDING = 2,
+    FRAME_RAISED = 3,
+    FRAME_CLEARED = 4
+};
+
+typedef signed char PyFrameState;
+
 typedef struct {
     int b_type;                 /* what kind of block this is */
     int b_handler;              /* where to jump to find handler */
@@ -18,11 +33,8 @@ struct _frame {
     PyObject *f_globals;        /* global symbol table (PyDictObject) */
     PyObject *f_locals;         /* local symbol table (any mapping) */
     PyObject **f_valuestack;    /* points after the last local */
-    /* Next free slot in f_valuestack.  Frame creation sets to f_valuestack.
-       Frame evaluation usually NULLs it, but a frame that yields sets it
-       to the current stack top. */
-    PyObject **f_stacktop;
     PyObject *f_trace;          /* Trace function */
+    int f_stackdepth;           /* Depth of value stack */
     char f_trace_lines;         /* Emit per-line trace events? */
     char f_trace_opcodes;       /* Emit per-opcode trace events? */
 
@@ -37,11 +49,22 @@ struct _frame {
        bytecode index. */
     int f_lineno;               /* Current line number */
     int f_iblock;               /* index in f_blockstack */
-    char f_executing;           /* whether the frame is still executing */
+    PyFrameState f_state;       /* What state the frame is in */
     PyTryBlock f_blockstack[CO_MAXBLOCKS]; /* for try and loop blocks */
     PyObject *f_localsplus[1];  /* locals+stack, dynamically sized */
 };
 
+static inline int _PyFrame_IsRunnable(struct _frame *f) {
+    return f->f_state < FRAME_EXECUTING;
+}
+
+static inline int _PyFrame_IsExecuting(struct _frame *f) {
+    return f->f_state == FRAME_EXECUTING;
+}
+
+static inline int _PyFrameHasCompleted(struct _frame *f) {
+    return f->f_state > FRAME_EXECUTING;
+}
 
 /* Standard object interface */