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authorMiguel Sofer <miguel.sofer@gmail.com>2007-08-19 18:59:13 (GMT)
committerMiguel Sofer <miguel.sofer@gmail.com>2007-08-19 18:59:13 (GMT)
commit2d71d4d051e14c5b84f251b888c67cbc7b0fee99 (patch)
tree0e052afc7700294ce588ac894d3ba1346ed73d71
parent8742106ee7df13529f4cbd32c2c1a973ef21a730 (diff)
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* generic/tclExecute.c: changed the check for overflow in sums,
reducing objsize, number of branches and cache misses (according to cachegrind). Non-overflow for s=a+b: previous ((a >= 0 || b >= 0 || s < 0) && (s >= 0 || b < 0 || a < 0)) now (((a^s) >= 0) || ((a^b) < 0)) This expresses: "a and s have the same sign or else a and b have different sign".
-rw-r--r--ChangeLog12
-rw-r--r--generic/tclExecute.c30
2 files changed, 24 insertions, 18 deletions
diff --git a/ChangeLog b/ChangeLog
index ce60f24..b25d6f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2007-08-19 Miguel Sofer <msofer@users.sf.net>
+
+ * generic/tclExecute.c: changed the check for overflow in sums,
+ reducing objsize, number of branches and cache misses (according
+ to cachegrind). Non-overflow for s=a+b:
+ previous
+ ((a >= 0 || b >= 0 || s < 0) && (s >= 0 || b < 0 || a < 0))
+ now
+ (((a^s) >= 0) || ((a^b) < 0))
+ This expresses: "a and s have the same sign or else a and b have
+ different sign".
+
2007-08-19 Donal K. Fellows <dkf@users.sf.net>
* doc/interp.n (RESOURCE LIMITS): Added text to better explain why
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 5b3185b..57296fb 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -12,7 +12,7 @@
* See the file "license.terms" for information on usage and redistribution of
* this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
- * RCS: @(#) $Id: tclExecute.c,v 1.315 2007/08/16 20:39:34 msofer Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.316 2007/08/19 18:59:15 msofer Exp $
*/
#include "tclInt.h"
@@ -1317,11 +1317,11 @@ TclIncrObj(
long sum = augend + addend;
/*
- * Test for overflow.
+ * Overflow when (augend and sum have different sign) and
+ * (augend and i have the same sign)
*/
-
- if ((augend >= 0 || addend >= 0 || sum < 0)
- && (sum >= 0 || addend < 0 || augend < 0)) {
+
+ if (((augend^sum) >= 0) || ((augend^addend) < 0) ) {
TclSetLongObj(valuePtr, sum);
return TCL_OK;
}
@@ -1369,8 +1369,7 @@ TclIncrObj(
* Check for overflow.
*/
- if ((w1 >= 0 || w2 >= 0 || sum < 0)
- && (w1 < 0 || w2 < 0 || sum >= 0)) {
+ if (((w1^sum) >= 0) || (w1^w2) < 0) {
Tcl_SetWideIntObj(valuePtr, sum);
return TCL_OK;
}
@@ -2807,13 +2806,11 @@ TclExecuteByteCode(
long sum = augend + i;
/*
- * Test for overflow.
- * TODO: faster checking with known limits on i?
+ * Overflow when (augend and sum have different sign) and
+ * (augend and i have the same sign)
*/
- if ((augend >= 0 || i >= 0 || sum < 0)
- && (sum >= 0 || i < 0 || augend < 0)) {
-
+ if (((augend^sum) >= 0) || ((augend^i) < 0) ) {
TRACE(("%u %ld => ", opnd, i));
if (Tcl_IsShared(objPtr)) {
objPtr->refCount--; /* We know it's shared. */
@@ -2861,8 +2858,7 @@ TclExecuteByteCode(
* Check for overflow.
*/
- if ((w >= 0 || i >= 0 || sum < 0)
- && (w < 0 || i < 0 || sum >= 0)) {
+ if (((w^sum) >= 0) || ((w^i) < 0)) {
TRACE(("%u %ld => ", opnd, i));
if (Tcl_IsShared(objPtr)) {
objPtr->refCount--; /* We know it's shared. */
@@ -5275,8 +5271,7 @@ TclExecuteByteCode(
* Check for overflow.
*/
- if (((w1 < 0) && (w2 < 0) && (wResult >= 0))
- || ((w1 > 0) && (w2 > 0) && (wResult < 0))) {
+ if (((w1^wResult) < 0) && ((w1^w2) >= 0)) {
goto overflow;
}
}
@@ -5292,8 +5287,7 @@ TclExecuteByteCode(
* Must check for overflow.
*/
- if (((w1 < 0) && (w2 > 0) && (wResult > 0))
- || ((w1 >= 0) && (w2 < 0) && (wResult < 0))) {
+ if (((w1^wResult) < 0) && ((w1^w2) < 0)) {
goto overflow;
}
}