Performance tweak: allow stack_pointer and oparg to be register variables.

SF patch #943898

diff --git a/Python/ceval.c b/Python/ceval.c
index a52168c71fd9c3a90ad4ea5d8a8d7c00749d110d..f66e318f5819c79b83fbeeffe2831e55e84edb59 100644 (file)
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -464,10 +464,10 @@ eval_frame(PyFrameObject *f)
 #ifdef DXPAIRS
        int lastopcode = 0;
 #endif
-       PyObject **stack_pointer; /* Next free slot in value stack */
+       register PyObject **stack_pointer;   /* Next free slot in value stack */
        register unsigned char *next_instr;
-       register int opcode=0;  /* Current opcode */
-       register int oparg=0;   /* Current opcode argument, if any */
+       register int opcode;    /* Current opcode */
+       register int oparg;     /* Current opcode argument, if any */
        register enum why_code why; /* Reason for block stack unwind */
        register int err;       /* Error status -- nonzero if error */
        register PyObject *x;   /* Result object -- NULL if error */
@@ -807,6 +807,8 @@ eval_frame(PyFrameObject *f)
                /* Extract opcode and argument */
 
                opcode = NEXTOP();
+               oparg = 0;   /* allows oparg to be stored in a register because
+                       it doesn't have to be remembered across a full loop */
                if (HAS_ARG(opcode))
                        oparg = NEXTARG();
          dispatch_opcode:
@@ -2095,16 +2097,21 @@ eval_frame(PyFrameObject *f)
                        continue;
 
                case CALL_FUNCTION:
+               {
+                       PyObject **sp;
                        PCALL(PCALL_ALL);
+                       sp = stack_pointer;
 #ifdef WITH_TSC
-                       x = call_function(&stack_pointer, oparg, &intr0, &intr1);
+                       x = call_function(&sp, oparg, &intr0, &intr1);
 #else
-                       x = call_function(&stack_pointer, oparg);
+                       x = call_function(&sp, oparg);
 #endif
+                       stack_pointer = sp;
                        PUSH(x);
                        if (x != NULL)
                                continue;
                        break;
+               }
 
                case CALL_FUNCTION_VAR:
                case CALL_FUNCTION_KW:
@@ -2114,7 +2121,7 @@ eval_frame(PyFrameObject *f)
                    int nk = (oparg>>8) & 0xff;
                    int flags = (opcode - CALL_FUNCTION) & 3;
                    int n = na + 2 * nk;
-                   PyObject **pfunc, *func;
+                   PyObject **pfunc, *func, **sp;
                    PCALL(PCALL_ALL);
                    if (flags & CALL_FLAG_VAR)
                            n++;
@@ -2135,13 +2142,15 @@ eval_frame(PyFrameObject *f)
                            n++;
                    } else
                            Py_INCREF(func);
+                   sp = stack_pointer;
 #ifdef WITH_TSC
                    rdtscll(intr0);
 #endif
-                   x = ext_do_call(func, &stack_pointer, flags, na, nk);
+                   x = ext_do_call(func, &sp, flags, na, nk);
 #ifdef WITH_TSC
                    rdtscll(intr1);
 #endif
+                   stack_pointer = sp;
                    Py_DECREF(func);
 
                    while (stack_pointer > pfunc) {