XBUG 7302 supplement. Even with the prior change, the chances of the

cache being rendered invalid were high due to the way the modmix table
was seeded. When the modifier combinations have hight order bits set
the hash results when subsequent combinations without the high order
bits is the same and the cache entry will be overwritten. This results
in the key-translator being called more times than is necessary. By
seeding the modmix table differently it's possible to arrange for
the hash to produce a different index for modifier combinations with
the high bit set and we see a significant reduction in the number of
times that the key-translator is called in most cases.

1 files changed, 20 insertions, 20 deletions

diff --git a/xc/lib/Xt/TMkey.c b/xc/lib/Xt/TMkey.c
index 9f18b1fcb..14b7bb941 100644
--- a/xc/lib/Xt/TMkey.c
+++ b/xc/lib/Xt/TMkey.c
@@ -1,4 +1,4 @@
-/* $XConsortium: TMkey.c,v 1.28 95/06/22 15:01:14 kaleb Exp $ */
+/* $XConsortium: TMkey.c,v 1.29 95/06/22 15:08:31 kaleb Exp $ */
 /*LINTLIBRARY*/
 
 /***********************************************************
@@ -88,8 +88,24 @@ in this Software without prior written authorization from the X Consortium.
 
 #define FM(i) i >> (8 - TMKEYCACHELOG2)
 static Const unsigned char modmix[256] = {
-FM(0x00), FM(0x80), FM(0x40), FM(0xc0), FM(0x20), FM(0xa0), FM(0x60), FM(0xe0),
-FM(0x10), FM(0x90), FM(0x50), FM(0xd0), FM(0x30), FM(0xb0), FM(0x70), FM(0xf0),
+FM(0x0f), FM(0x8f), FM(0x4f), FM(0xcf), FM(0x2f), FM(0xaf), FM(0x6f), FM(0xef),
+FM(0x1f), FM(0x9f), FM(0x5f), FM(0xdf), FM(0x3f), FM(0xbf), FM(0x7f), FM(0xff),
+FM(0x07), FM(0x87), FM(0x47), FM(0xc7), FM(0x27), FM(0xa7), FM(0x67), FM(0xe7),
+FM(0x17), FM(0x97), FM(0x57), FM(0xd7), FM(0x37), FM(0xb7), FM(0x77), FM(0xf7),
+FM(0x0b), FM(0x8b), FM(0x4b), FM(0xcb), FM(0x2b), FM(0xab), FM(0x6b), FM(0xeb),
+FM(0x1b), FM(0x9b), FM(0x5b), FM(0xdb), FM(0x3b), FM(0xbb), FM(0x7b), FM(0xfb),
+FM(0x03), FM(0x83), FM(0x43), FM(0xc3), FM(0x23), FM(0xa3), FM(0x63), FM(0xe3),
+FM(0x13), FM(0x93), FM(0x53), FM(0xd3), FM(0x33), FM(0xb3), FM(0x73), FM(0xf3),
+FM(0x0d), FM(0x8d), FM(0x4d), FM(0xcd), FM(0x2d), FM(0xad), FM(0x6d), FM(0xed),
+FM(0x1d), FM(0x9d), FM(0x5d), FM(0xdd), FM(0x3d), FM(0xbd), FM(0x7d), FM(0xfd),
+FM(0x05), FM(0x85), FM(0x45), FM(0xc5), FM(0x25), FM(0xa5), FM(0x65), FM(0xe5),
+FM(0x15), FM(0x95), FM(0x55), FM(0xd5), FM(0x35), FM(0xb5), FM(0x75), FM(0xf5),
+FM(0x09), FM(0x89), FM(0x49), FM(0xc9), FM(0x29), FM(0xa9), FM(0x69), FM(0xe9),
+FM(0x19), FM(0x99), FM(0x59), FM(0xd9), FM(0x39), FM(0xb9), FM(0x79), FM(0xf9),
+FM(0x01), FM(0x81), FM(0x41), FM(0xc1), FM(0x21), FM(0xa1), FM(0x61), FM(0xe1),
+FM(0x11), FM(0x91), FM(0x51), FM(0xd1), FM(0x31), FM(0xb1), FM(0x71), FM(0xf1),
+FM(0x00), FM(0x8e), FM(0x4e), FM(0xce), FM(0x2e), FM(0xae), FM(0x6e), FM(0xee),
+FM(0x1e), FM(0x9e), FM(0x5e), FM(0xde), FM(0x3e), FM(0xbe), FM(0x7e), FM(0xfe),
 FM(0x08), FM(0x88), FM(0x48), FM(0xc8), FM(0x28), FM(0xa8), FM(0x68), FM(0xe8),
 FM(0x18), FM(0x98), FM(0x58), FM(0xd8), FM(0x38), FM(0xb8), FM(0x78), FM(0xf8),
 FM(0x04), FM(0x84), FM(0x44), FM(0xc4), FM(0x24), FM(0xa4), FM(0x64), FM(0xe4),
@@ -103,23 +119,7 @@ FM(0x1a), FM(0x9a), FM(0x5a), FM(0xda), FM(0x3a), FM(0xba), FM(0x7a), FM(0xfa),
 FM(0x06), FM(0x86), FM(0x46), FM(0xc6), FM(0x26), FM(0xa6), FM(0x66), FM(0xe6),
 FM(0x16), FM(0x96), FM(0x56), FM(0xd6), FM(0x36), FM(0xb6), FM(0x76), FM(0xf6),
 FM(0x0e), FM(0x8e), FM(0x4e), FM(0xce), FM(0x2e), FM(0xae), FM(0x6e), FM(0xee),
-FM(0x1e), FM(0x9e), FM(0x5e), FM(0xde), FM(0x3e), FM(0xbe), FM(0x7e), FM(0xfe),
-FM(0x01), FM(0x81), FM(0x41), FM(0xc1), FM(0x21), FM(0xa1), FM(0x61), FM(0xe1),
-FM(0x11), FM(0x91), FM(0x51), FM(0xd1), FM(0x31), FM(0xb1), FM(0x71), FM(0xf1),
-FM(0x09), FM(0x89), FM(0x49), FM(0xc9), FM(0x29), FM(0xa9), FM(0x69), FM(0xe9),
-FM(0x19), FM(0x99), FM(0x59), FM(0xd9), FM(0x39), FM(0xb9), FM(0x79), FM(0xf9),
-FM(0x05), FM(0x85), FM(0x45), FM(0xc5), FM(0x25), FM(0xa5), FM(0x65), FM(0xe5),
-FM(0x15), FM(0x95), FM(0x55), FM(0xd5), FM(0x35), FM(0xb5), FM(0x75), FM(0xf5),
-FM(0x0d), FM(0x8d), FM(0x4d), FM(0xcd), FM(0x2d), FM(0xad), FM(0x6d), FM(0xed),
-FM(0x1d), FM(0x9d), FM(0x5d), FM(0xdd), FM(0x3d), FM(0xbd), FM(0x7d), FM(0xfd),
-FM(0x03), FM(0x83), FM(0x43), FM(0xc3), FM(0x23), FM(0xa3), FM(0x63), FM(0xe3),
-FM(0x13), FM(0x93), FM(0x53), FM(0xd3), FM(0x33), FM(0xb3), FM(0x73), FM(0xf3),
-FM(0x0b), FM(0x8b), FM(0x4b), FM(0xcb), FM(0x2b), FM(0xab), FM(0x6b), FM(0xeb),
-FM(0x1b), FM(0x9b), FM(0x5b), FM(0xdb), FM(0x3b), FM(0xbb), FM(0x7b), FM(0xfb),
-FM(0x07), FM(0x87), FM(0x47), FM(0xc7), FM(0x27), FM(0xa7), FM(0x67), FM(0xe7),
-FM(0x17), FM(0x97), FM(0x57), FM(0xd7), FM(0x37), FM(0xb7), FM(0x77), FM(0xf7),
-FM(0x0f), FM(0x8f), FM(0x4f), FM(0xcf), FM(0x2f), FM(0xaf), FM(0x6f), FM(0xef),
-FM(0x1f), FM(0x9f), FM(0x5f), FM(0xdf), FM(0x3f), FM(0xbf), FM(0x7f), FM(0xff)
+FM(0x1e), FM(0x9e), FM(0x5e), FM(0xde), FM(0x3e), FM(0xbe), FM(0x7e), FM(0xfe)
 };
 #undef FM