From 7dc52212aa022e7417d3fc32422db646b8a881a0 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Sun, 16 Mar 2003 20:14:44 +0000
Subject: [PATCH] Eliminate data dependency in predict macro. Added two
 predictions:   GET_ITER --> FOR_ITER   FOR_ITER --> STORE_FAST or
 UNPACK_SEQUENCE

Improves timings on pybench and timeit.py. Pystone results are neutral.
---
 Python/ceval.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Python/ceval.c b/Python/ceval.c
index 38edb73bd06..f965d3866bb 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -620,8 +620,8 @@ eval_frame(PyFrameObject *f)
 
 #define PREDICT(op)		if (*next_instr == op) goto PRED_##op
 #define PREDICTED(op)		PRED_##op: next_instr++
-#define PREDICTED_WITH_ARG(op)	PRED_##op: oparg = (next_instr += 3, \
-				(next_instr[-1]<<8) + next_instr[-2])
+#define PREDICTED_WITH_ARG(op)	PRED_##op: oparg = (next_instr[2]<<8) + \
+				next_instr[1]; next_instr += 3
 
 /* Stack manipulation macros */
 
@@ -889,6 +889,7 @@ eval_frame(PyFrameObject *f)
 			PUSH(x);
 			goto fast_next_opcode;
 
+		PREDICTED_WITH_ARG(STORE_FAST);
 		case STORE_FAST:
 			v = POP();
 			SETLOCAL(oparg, v);
@@ -1675,6 +1676,7 @@ eval_frame(PyFrameObject *f)
 							NAME_ERROR_MSG ,w);
 			break;
 
+		PREDICTED_WITH_ARG(UNPACK_SEQUENCE);
 		case UNPACK_SEQUENCE:
 			v = POP();
 			if (PyTuple_CheckExact(v)) {
@@ -2051,17 +2053,21 @@ eval_frame(PyFrameObject *f)
 			Py_DECREF(v);
 			if (x != NULL) {
 				SET_TOP(x);
+				PREDICT(FOR_ITER);
 				continue;
 			}
 			STACKADJ(-1);
 			break;
 
+		PREDICTED_WITH_ARG(FOR_ITER);
 		case FOR_ITER:
 			/* before: [iter]; after: [iter, iter()] *or* [] */
 			v = TOP();
 			x = PyIter_Next(v);
 			if (x != NULL) {
 				PUSH(x);
+				PREDICT(STORE_FAST);
+				PREDICT(UNPACK_SEQUENCE);
 				continue;
 			}
 			if (!PyErr_Occurred()) {