[Python-checkins] python/dist/src/Python ceval.c,2.354,2.355
rhettinger@users.sourceforge.net
rhettinger@users.sourceforge.net
2003年3月15日 19:11:07 -0800
Update of /cvsroot/python/python/dist/src/Python
In directory sc8-pr-cvs1:/tmp/cvs-serv12161
Modified Files:
ceval.c
Log Message:
Introduced macros for a simple opcode prediction protocol.
Applied to common cases:
COMPARE_OP is often followed by a JUMP_IF.
JUMP_IF is usually followed by POP_TOP.
Shows improved timings on PyStone, PyBench, and specific tests
using timeit.py:
python timeit.py -s "x=1" "if x==1: pass"
python timeit.py -s "x=1" "if x==2: pass"
python timeit.py -s "x=1" "if x: pass"
python timeit.py -s "x=100" "while x!=1: x-=1"
Potential future candidates:
GET_ITER predicts FOR_ITER
FOR_ITER predicts STORE_FAST or UNPACK_SEQUENCE
Also, applied missing goto fast_next_opcode to DUP_TOPX.
Index: ceval.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Python/ceval.c,v
retrieving revision 2.354
retrieving revision 2.355
diff -C2 -d -r2.354 -r2.355
*** ceval.c 14 Mar 2003 01:37:42 -0000 2.354
--- ceval.c 16 Mar 2003 03:11:04 -0000 2.355
***************
*** 603,606 ****
--- 603,626 ----
#define JUMPBY(x) (next_instr += (x))
+ /* OpCode prediction macros
+ Some opcodes tend to come in pairs thus making it possible to predict
+ the second code when the first is run. For example, COMPARE_OP is often
+ followed by JUMP_IF_FALSE or JUMP_IF_TRUE. And, those opcodes are often
+ followed by a POP_TOP.
+
+ Verifying the prediction costs a single high-speed test of register
+ variable against a constant. If the pairing was good, then the odds
+ processor has a high likelihood of making its own successful branch
+ prediction which results in a nearly zero overhead transition to the
+ next opcode.
+
+ A successful prediction saves a trip through the eval-loop including
+ its two unpredictable branches, the HASARG test and the switch-case.
+ */
+
+ #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])
+
/* Stack manipulation macros */
***************
*** 874,877 ****
--- 894,898 ----
goto fast_next_opcode;
+ PREDICTED(POP_TOP);
case POP_TOP:
v = POP();
***************
*** 921,925 ****
SET_TOP(x);
SET_SECOND(w);
! continue;
} else if (oparg == 3) {
x = TOP();
--- 942,946 ----
SET_TOP(x);
SET_SECOND(w);
! goto fast_next_opcode;
} else if (oparg == 3) {
x = TOP();
***************
*** 933,937 ****
SET_SECOND(w);
SET_THIRD(v);
! continue;
}
Py_FatalError("invalid argument to DUP_TOPX"
--- 954,958 ----
SET_SECOND(w);
SET_THIRD(v);
! goto fast_next_opcode;
}
Py_FatalError("invalid argument to DUP_TOPX"
***************
*** 1919,1924 ****
Py_DECREF(w);
SET_TOP(x);
! if (x != NULL) continue;
! break;
case IMPORT_NAME:
--- 1940,1947 ----
Py_DECREF(w);
SET_TOP(x);
! if (x == NULL) break;
! PREDICT(JUMP_IF_FALSE);
! PREDICT(JUMP_IF_TRUE);
! continue;
case IMPORT_NAME:
***************
*** 1975,1982 ****
goto fast_next_opcode;
case JUMP_IF_FALSE:
w = TOP();
! if (w == Py_True)
goto fast_next_opcode;
if (w == Py_False) {
JUMPBY(oparg);
--- 1998,2008 ----
goto fast_next_opcode;
+ PREDICTED_WITH_ARG(JUMP_IF_FALSE);
case JUMP_IF_FALSE:
w = TOP();
! if (w == Py_True) {
! PREDICT(POP_TOP);
goto fast_next_opcode;
+ }
if (w == Py_False) {
JUMPBY(oparg);
***************
*** 1992,1999 ****
continue;
case JUMP_IF_TRUE:
w = TOP();
! if (w == Py_False)
goto fast_next_opcode;
if (w == Py_True) {
JUMPBY(oparg);
--- 2018,2028 ----
continue;
+ PREDICTED_WITH_ARG(JUMP_IF_TRUE);
case JUMP_IF_TRUE:
w = TOP();
! if (w == Py_False) {
! PREDICT(POP_TOP);
goto fast_next_opcode;
+ }
if (w == Py_True) {
JUMPBY(oparg);