From: Jeff Law <law@redhat.com>
To: "Martin Liška" <mliska@suse.cz>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Fix bitmap_bit_in_range_p (PR tree-optimization/82493).
Date: Fri, 13 Oct 2017 15:04:00 -0000 [thread overview]
Message-ID: <190c5684-631c-a7a0-631e-c1296081e3f0@redhat.com> (raw)
In-Reply-To: <2903a0d3-a2f1-791e-bff9-0d5939832dfa@suse.cz>
On 10/13/2017 07:02 AM, Martin Liška wrote:
> On 10/12/2017 11:54 PM, Jeff Law wrote:
>> On 10/11/2017 12:13 AM, Martin Liška wrote:
>>> 2017-10-10 Martin Liska <mliska@suse.cz>
>>>
>>> PR tree-optimization/82493
>>> * sbitmap.c (bitmap_bit_in_range_p): Fix the implementation.
>>> (test_range_functions): New function.
>>> (sbitmap_c_tests): Likewise.
>>> * selftest-run-tests.c (selftest::run_tests): Run new tests.
>>> * selftest.h (sbitmap_c_tests): New function.
>> I went ahead and committed this along with a patch to fix the off-by-one
>> error in live_bytes_read. Bootstrapped and regression tested on x86.
>>
>> Actual patch attached for archival purposes.
>>
>> Jeff
>>
>
> Hello.
>
> I wrote a patch that adds various gcc_checking_asserts and I hit following:
>
> ./xgcc -B. /home/marxin/Programming/gcc/gcc/testsuite/gfortran.dg/char_result_12.f90 -c -O2
> during GIMPLE pass: dse
> /home/marxin/Programming/gcc/gcc/testsuite/gfortran.dg/char_result_12.f90:7:0:
>
> program testat
>
> internal compiler error: in bitmap_check_index, at sbitmap.h:105
> 0x1c014c1 bitmap_check_index
> ../../gcc/sbitmap.h:105
> 0x1c01fa7 bitmap_bit_in_range_p(simple_bitmap_def const*, unsigned int, unsigned int)
> ../../gcc/sbitmap.c:335
> 0x1179002 live_bytes_read
> ../../gcc/tree-ssa-dse.c:497
> 0x117935a dse_classify_store
> ../../gcc/tree-ssa-dse.c:595
> 0x1179947 dse_dom_walker::dse_optimize_stmt(gimple_stmt_iterator*)
> ../../gcc/tree-ssa-dse.c:786
> 0x1179b6e dse_dom_walker::before_dom_children(basic_block_def*)
> ../../gcc/tree-ssa-dse.c:853
> 0x1a6f659 dom_walker::walk(basic_block_def*)
> ../../gcc/domwalk.c:308
> 0x1179cb9 execute
> ../../gcc/tree-ssa-dse.c:907
>
> Where we call:
> Breakpoint 1, bitmap_bit_in_range_p (bmap=0x29d6cd0, start=0, end=515) at ../../gcc/sbitmap.c:335
> 335 bitmap_check_index (bmap, end);
> (gdb) p *bmap
> $1 = {n_bits = 256, size = 4, elms = {255}}
>
> Is it a valid call or should caller check indices?
It doesn't look valid to me. I'll dig into it.
In general the sbitmap interface requires callers to DTRT -- failure can
easily lead to an out of bounds read or write. It's one of the things I
really dislike about the sbitmap implementation.
So it's safe to assume that I'm fully supportive of adding more testing
to catch this kind thing.
Jeff
next prev parent reply other threads:[~2017-10-13 14:59 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-11 6:15 Martin Liška
2017-10-11 17:58 ` Jeff Law
2017-10-12 4:48 ` Jeff Law
2017-10-12 22:16 ` Jeff Law
2017-10-13 8:01 ` Martin Liška
2017-10-13 13:13 ` Martin Liška
2017-10-13 14:17 ` Jeff Law
2017-10-13 13:03 ` Martin Liška
2017-10-13 15:04 ` Jeff Law [this message]
2017-10-16 12:15 ` Martin Liška
2017-10-16 14:53 ` Jeff Law
2017-10-17 17:33 ` Jeff Law
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