Speed up the disassembler by allowing prefixed instruction tables

Modify the disassembler so that we can have separate instruction
tables for prefixed instructions.  As it was, all instructions which
started with 0F were linearly searched, and that is by now more than
half the instruction set.

1 files changed, 11 insertions, 2 deletions

diff --git a/disasm.c b/disasm.c
index 3a8f710d..a6c1c729 100644
--- a/disasm.c
+++ b/disasm.c
@@ -671,9 +671,11 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
             int32_t offset, int autosync, uint32_t prefer)
 {
     const struct itemplate * const *p, * const *best_p;
+    const struct disasm_index *ix;
+    uint8_t *dp;
     int length, best_length = 0;
     char *segover;
-    int i, slen, colon;
+    int i, slen, colon, n;
     uint8_t *origdata;
     int works;
     insn tmp_ins, ins;
@@ -728,7 +730,14 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
     best_p = NULL;
     best_pref = INT_MAX;
 
-    for (p = itable[*data]; *p; p++) {
+    dp = data;
+    ix = itable + *dp++;
+    while (ix->n == (size_t)-1) {
+	ix = (const struct disasm_index *)ix->p + *dp++;
+    }
+
+    p = (const struct itemplate * const *)ix->p;
+    for (n = ix->n; n; n--, p++) {
         if ((length = matches(*p, data, &prefix, segsize, &tmp_ins))) {
             works = TRUE;
             /*