[PATCH][genattrtab] Fix memory corruption, allocate enough memory for all bypassed reservations

[Kyrill Tkachov <kyrylo dot tkachov at arm dot com>]

Hi all,

I noticed a memory corruption bug while adding some scheduler bypasses 
in the arm backend.
genattrtab would segfault while processing the bypasses. Valgrind 
confirmed this.

The problem is that when processing the bypassed reservations, 
make_automaton_pairs allocates memory in proportion to the number of 
defined bypasses rather than the number of bypassed reservations. This 
means that if the number of bypassed reservations is sufficiently larger 
than the number of bypasses, the loop will overwrite unallocated memory.

I also observed this effect on aarch64, but there was no segfault there, 
presumably because the number of reservations in aarch64 is much smaller 
than arm at the moment (we only use two pipeline descriptions in aarch64).

This patch fixes that and valgrind confirms that there's no out of 
bounds accesses now.

Bootstrapped and tested arm-none-linux-gnueabihf, 
aarch64-none-linux-gnu, x86_64-linux.

Ok for trunk?

Thanks,
Kyrill

2014-06-13  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    * genattrtab.c (n_bypassed): New variable.
    (process_bypasses): Initialise n_bypassed.
    Count number of bypassed reservations.
    (make_automaton_attrs): Allocate space for bypassed reservations
    rather than number of bypasses.

diff --git a/gcc/genattrtab.c b/gcc/genattrtab.c
index c5ce51c..2b6b3ce 100644
--- a/gcc/genattrtab.c
+++ b/gcc/genattrtab.c
@@ -4766,6 +4766,7 @@ struct bypass_list
 
 static struct bypass_list *all_bypasses;
 static size_t n_bypasses;
+static size_t n_bypassed;
 
 static void
 gen_bypass_1 (const char *s, size_t len)
@@ -4811,12 +4812,19 @@ process_bypasses (void)
   struct bypass_list *b;
   struct insn_reserv *r;
 
+  n_bypassed = 0;
+
   /* The reservation list is likely to be much longer than the bypass
      list.  */
   for (r = all_insn_reservs; r; r = r->next)
     for (b = all_bypasses; b; b = b->next)
       if (fnmatch (b->pattern, r->name, 0) == 0)
-	r->bypassed = true;
+        {
+          if (!r->bypassed)
+            n_bypassed++;
+
+          r->bypassed = true;
+        }
 }
 
 /* Check that attribute NAME is used in define_insn_reservation condition
@@ -5075,7 +5083,7 @@ make_automaton_attrs (void)
       process_bypasses ();
 
       byps_exp = rtx_alloc (COND);
-      XVEC (byps_exp, 0) = rtvec_alloc (n_bypasses * 2);
+      XVEC (byps_exp, 0) = rtvec_alloc (n_bypassed * 2);
       XEXP (byps_exp, 1) = make_numeric_value (0);
       for (decl = all_insn_reservs, i = 0;
 	   decl;