Hi!
On Wed, Nov 15, 2017 at 08:31:00AM +0100, Martin Liška wrote:
> On 11/08/2017 05:31 PM, Jeff Law wrote:
> > I don't see an updated patch in this thread? THe last message I see is
> > this one where you indicate you're going to tweak the patch and re-test.
> >
> > Jeff
>
> Yes, I tweaked and tested following patch.
>
> Martin
> >From a369ac78b887e219a375e17d6817c1f744e71779 Mon Sep 17 00:00:00 2001
> From: marxin <mli...@suse.cz>
> Date: Thu, 19 Oct 2017 13:38:01 +0200
> Subject: [PATCH] Fix UBSAN errors in dse.c (PR rtl-optimization/82044).
>
> gcc/ChangeLog:
>
> 2017-10-19 Martin Liska <mli...@suse.cz>
>
> PR rtl-optimization/82044
> PR tree-optimization/82042
> * dse.c (check_mem_read_rtx): Check for overflow.
Unfortunately this patch broke i686-linux bootstrap, during stage2
libgcc configure fails due to numerous ICEs.
There are 2 problems with the patch:
1) if the mode of the read is BLKmode, then width is set to -1,
so offset > HOST_WIDE_INT_MAX - width invokes UB at compile time
and is true for any offset > HOST_WIDE_INT_MIN if the compiler wraps
the result around.
2) clear_rhs_from_active_local_stores () is the punt action in record_store,
but not in check_mem_read_rtx, where e.g. a few lines above it if
canon_address fails it does add_wild_read instead.
The following patch fixes those two issues and adds similar overflow
check to record_store too (in that spot width is always non-negative, so
we don't need a special width == -1 handling).
Bootstrapped successfully on i686-linux, ok for trunk if it passes regtest
there (and pending x86_64-linux bootstrap + regtest)?
2017-11-21 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/82044
PR tree-optimization/82042
* dse.c (record_store): Check for overflow.
(check_mem_read_rtx): Properly check for overflow if width == -1, call
add_wild_read instead of clear_rhs_from_active_local_stores on
overflow and log it into dump_file.
--- gcc/dse.c.jj 2017-11-21 23:18:18.000000000 +0100
+++ gcc/dse.c 2017-11-21 23:28:08.952439915 +0100
@@ -1342,6 +1342,12 @@ record_store (rtx body, bb_info_t bb_inf
else
width = GET_MODE_SIZE (GET_MODE (mem));
+ if (offset > HOST_WIDE_INT_MAX - width)
+ {
+ clear_rhs_from_active_local_stores ();
+ return 0;
+ }
+
if (group_id >= 0)
{
/* In the restrictive case where the base is a constant or the
@@ -1981,9 +1987,13 @@ check_mem_read_rtx (rtx *loc, bb_info_t
else
width = GET_MODE_SIZE (GET_MODE (mem));
- if (offset > HOST_WIDE_INT_MAX - width)
+ if (width == -1
+ ? offset == HOST_WIDE_INT_MIN
+ : offset > HOST_WIDE_INT_MAX - width)
{
- clear_rhs_from_active_local_stores ();
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " adding wild read, due to overflow.\n");
+ add_wild_read (bb_info);
return;
}
Jakub
