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[PATCH, PR 49786] Avoid overflow when updating counts in IPA-CP
- From: Martin Jambor <mjambor at suse dot cz>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Jan Hubicka <hubicka at ucw dot cz>
- Date: Tue, 26 Jul 2011 13:11:50 +0200
- Subject: [PATCH, PR 49786] Avoid overflow when updating counts in IPA-CP
Hi,
the issue in PR 49786 has been well summarized in comment #12.
Basically, the multiplication we do when updating counts of edges
overflows. I looked at how this was handled previously in IPA-CP and
the following should be an equivalent solution.
This patch fixes the LTO profiled bootstrap and I have tested it by
doing a usual non-LTO and non-profiled bootstrap and testsuite
(without any issues) run as well as running the testsuite on the
compiler produced by the LTO profiled bootstrap. I compared the
second set of testsuite results with both the results obtained from a
revision before the IPA-CP submission and the current normal bootstrap
ones and it seemed fine (although there were a few dump scan
failures). (All of the above was done on x86_64-linux.)
So, OK for trunk?
Thanks,
Martin
2011-07-25 Martin Jambor <mjambor@suse.cz>
PR bootstrap/49786
* ipa-cp.c (update_profiling_info): Avoid overflow when updating
counts.
(update_specialized_profile): Likewise.
Index: src/gcc/ipa-cp.c
===================================================================
--- src.orig/gcc/ipa-cp.c
+++ src/gcc/ipa-cp.c
@@ -1877,7 +1877,6 @@ dump_profile_updates (struct cgraph_node
cgraph_node_name (cs->callee), (HOST_WIDE_INT) cs->count);
}
-
/* After a specialized NEW_NODE version of ORIG_NODE has been created, update
their profile information to reflect this. */
@@ -1923,12 +1922,14 @@ update_profiling_info (struct cgraph_nod
for (cs = new_node->callees; cs ; cs = cs->next_callee)
if (cs->frequency)
- cs->count = cs->count * new_sum / orig_node_count;
+ cs->count = cs->count * (new_sum * REG_BR_PROB_BASE
+ / orig_node_count) / REG_BR_PROB_BASE;
else
cs->count = 0;
for (cs = orig_node->callees; cs ; cs = cs->next_callee)
- cs->count = cs->count * remainder / orig_node_count;
+ cs->count = cs->count * (remainder * REG_BR_PROB_BASE
+ / orig_node_count) / REG_BR_PROB_BASE;
if (dump_file)
dump_profile_updates (orig_node, new_node);
@@ -1966,7 +1967,8 @@ update_specialized_profile (struct cgrap
for (cs = orig_node->callees; cs ; cs = cs->next_callee)
{
- gcov_type dec = cs->count * redirected_sum / orig_node_count;
+ gcov_type dec = cs->count * (redirected_sum * REG_BR_PROB_BASE
+ / orig_node_count) / REG_BR_PROB_BASE;
if (dec < cs->count)
cs->count -= dec;
else