[Bug tree-optimization/66828] New: [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[Bug tree-optimization/66828] New: [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

            Bug ID: 66828
           Summary: [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38:
                    runtime error: left shift of 72057594037927936 by 8
                    places cannot be represented in type 'long int'
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
                CC: thomas.preudhomme at arm dot com
  Target Milestone: ---

since r219525 bootstrap-ubsan shows:

gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of
72057594037927936 by 8 places cannot be represented in type 'long int'

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |5.2

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

Thomas Preud'homme <thopre01 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2015-07-13
     Ever confirmed|0                           |1

--- Comment #1 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
I'm having trouble to reproduce the bug. I do encounter some ubsan errors but
in other files (most notably in hwint.h). This might hide the errors in
tree-ssa-math-opts.c

Anyway, according to the line number the issue seems to come from the following
line:

for (i = 0; i < size; i++, inc <<= BITS_PER_MARKER)

size is guaranteed to be less or equal to 64 / BITS_PER_MARKER as per checks in
find_bswap_or_nop_1 (CASE_CONVERT) and in init_symbolic_number. However, this
means after the last execution of the body, inc is shift by more than 63 bits
in total.

I'm now testing a patch via bootstrap + regression testsuite.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #2 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
The C standard says nothing about the cumulative effect of several shift so I'm
guessing that the real issue is probably that the type is signed. Quoting C99
section 6.5.8 paragraph 4:

"If E1 has a signed type and nonnegative value, and E1 × 2E2 is representable
in the result type, then that is the resulting value; otherwise, the behavior
is undefined."

Which is the case for the last iteration.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf848

--- Comment #8 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
Note that radr://21372179 has been closed by Apple as "behaves as expected' so
that they believe the bug lies in the FSF gcc boehm-gc code.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #3 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Well, gcc is a C++ project so the C99 standard doesn't apply.

The C++ standard says:

5.8.2:

The value of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are
zero-filled. If E1 has an unsigned type, the value of the result is E1 × 2E2 ,
reduced modulo one more than the maximum value representable in the result
type. Otherwise, if E1 has a signed type and non-negative value, and E1 × 2E2
is representable in the corresponding unsigned type of the result type, then
that value, converted to the result type, is the resulting value; otherwise,
the
behavior is undefined.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf840

--- Comment #2 from Matthias Klose <doko at gcc dot gnu.org> ---
adding this to extra_headers in gcc/config.gcc, it gets installed into
<gcc_lib_dir>/include, adding it to tm_file results in a build error.  Not sure
where to add it ...

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #4 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Indeed, I always forget. But as it goes, the excerpt you quote from C++
standard is exactly the same as in C99 so that doesn't invalidate the remaining
of my analysis.

The testing for the new patch is almost finished running so I'll soon post
something up for review.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.2                         |5.3

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 5.2 is being released, adjusting target milestone to 5.3.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #6 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Created attachment 36078
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36078&action=edit
Use unsigned type for inc to have defined left shift

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #7 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
(In reply to Thomas Preud'homme from comment #6)
> Created attachment 36078 [details]
> Use unsigned type for inc to have defined left shift

Hi Markus,

Sorry for the delay, I got busy on some other bugs. Would you mind giving the
patch attached to the PR a go? I tried reproducing the issue but couldn't. I
did ran the regression testsuite though and it's all good.

Best regards.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #8 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Thomas Preud'homme from comment #7)
> (In reply to Thomas Preud'homme from comment #6)
> > Created attachment 36078 [details]
> > Use unsigned type for inc to have defined left shift
> 
> Sorry for the delay, I got busy on some other bugs. Would you mind giving
> the patch attached to the PR a go? I tried reproducing the issue but
> couldn't. I did ran the regression testsuite though and it's all good.

Well, the fix is obvious. So I would just commit it.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #9 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Author: thopre01
Date: Tue Jul 28 06:54:50 2015
New Revision: 226298

URL: https://gcc.gnu.org/viewcvs?rev=226298&root=gcc&view=rev
Log:
2015-07-28  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    PR tree-optimization/66828
    * tree-ssa-math-opts.c (perform_symbolic_merge): Change type of inc
    from int64_t to uint64_t.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-ssa-math-opts.c

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #10 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Thomas, could you backport your fix to the gcc-5 branch, so that we can close
this issue?

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #11 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Sure. Starting bootstrap and testing.

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

--- Comment #12 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Author: thopre01
Date: Tue Aug 11 07:58:07 2015
New Revision: 226775

URL: https://gcc.gnu.org/viewcvs?rev=226775&root=gcc&view=rev
Log:
2015-08-11  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    Backport from mainline
    2015-07-28  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR tree-optimization/66828
    * tree-ssa-math-opts.c (perform_symbolic_merge): Change type of inc
    from int64_t to uint64_t.

Modified:
    branches/gcc-5-branch/gcc/ChangeLog
    branches/gcc-5-branch/gcc/tree-ssa-math-opts.c

[Bug tree-optimization/66828] [5/6 Regression] gcc/tree-ssa-math-opts.c:2182:38: runtime error: left shift of 72057594037927936 by 8 places cannot be represented in type 'long int'

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66828

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #13 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Fixed, thanks.