[Bug c++/66572] New: [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[Bug c++/66572] New: [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[miyuki at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66572

            Bug ID: 66572
           Summary: [6 Regression] Bogus Wlogical-op warning for operands
                    coming from template instantiations
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: miyuki at gcc dot gnu.org
  Target Milestone: ---

Consider this example:

$ cat ./test.cc 
struct false_type
{
    static constexpr bool value = false;
};

struct true_type
{
    static constexpr bool value = true;
};

template<typename T>
struct is_unsigned : false_type {};

template<>
struct is_unsigned<unsigned> : true_type {};

template<typename T1, typename T2>
bool foo()
{
    return is_unsigned<T1>::value && is_unsigned<T2>::value;
}

int main()
{
    foo<unsigned, unsigned>();
}

$ g++ -Wlogical-op -std=c++11 ./test.cc 
./test.cc: In instantiation of 'bool foo() [with T1 = unsigned int; T2 =
unsigned int]':
./test.cc:25:29:   required from here
./test.cc:20:35: warning: logical 'and' of equal expressions [-Wlogical-op]
     return is_unsigned<T1>::value && is_unsigned<T2>::value;

IMHO GCC should not issue this warning: in this instantiation
(is_unsigned<unsigned>::value && is_unsigned<unsigned>::value) operator && is
indeed redundant, but that is not true for general case.

[Bug c++/66572] [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66572

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-06-17
                 CC|                            |manu at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
Not idea how to fix it, but it seems logical that we should not warn. Why is it
a regression?
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf056

--- Comment #2 from Gerhard Steinmetz <gerhard.steinmetz.fortran@t-online.de> ---
Hmm, there is always an ICE on my environment, for any used options.

[Bug c++/66572] [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[miyuki at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66572

--- Comment #2 from Mikhail Maltsev <miyuki at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #1)
> Why is it a regression?
Because GCC 5.1 and 4.9.2 do not issue such warning.
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Subject: [Bug middle-end/66429] ICE in expand_GOMP_SIMD_LAST_LANE
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf429

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Wed Jun 17 17:59:25 2015
New Revision: 224568

URL: https://gcc.gnu.org/viewcvs?rev"4568&root=gcc&view=rev
Log:
        PR middle-end/66429
        * omp-low.c (expand_omp_taskreg): Use child_cfun instead of
        DECL_STRUCT_FUNCTION (child_fn).  Or in has_simduid_loops
        and has_force_vectorize_loops flags from cfun into
        child_cfun.
        (expand_omp_simd): For broken loop, set cfun->has_simduid_loops
        if simduid is non-NULL.
        * tree-pass.h (make_pass_simduid_cleanup): New prototype.
        * passes.def (pass_simduid_cleanup): Add new pass after loop
        passes.
        * tree-vectorizer.c (adjust_simduid_builtins): Remove one unnecessary
        indirection from htab argument's type.
        (shrink_simd_arrays): New function.
        (vectorize_loops): Use it.  Adjust adjust_simduid_builtins caller.
        Don't call adjust_simduid_builtins if there are no loops.
        (pass_data_simduid_cleanup, pass_simduid_cleanup): New variables.
        (pass_simduid_cleanup::execute): New method.
        (make_pass_simduid_cleanup): New function.

        * c-c++-common/gomp/pr66429.c: New test.

Added:
    trunk/gcc/testsuite/c-c++-common/gomp/pr66429.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/omp-low.c
    trunk/gcc/passes.def
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-pass.h
    trunk/gcc/tree-vectorizer.c

[Bug c++/66572] [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[miyuki at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66572

--- Comment #3 from Mikhail Maltsev <miyuki at gcc dot gnu.org> ---
Started with r222408. The commit message says:

PR c/63357
* c-common.c (warn_logical_operator): Warn if the operands have the same
expressions.
* doc/invoke.texi: Update description of -Wlogical-op.

Apperntly, the warning about same expressions in a logical expression was added
to Wlogical-op after GCC 5.1 release (I didn't know that) and it had this
problem from the very beginning.

In warn_logical_operator we have a check:

  /* We do not warn for constants because they are typical of macro
     expansions that test for features.  */
  if (CONSTANT_CLASS_P (op_left) || CONSTANT_CLASS_P (op_right))
    return;

But in this case op_left and op_right are:
<var_decl 0x7ffff6118bd0 value
    type <boolean_type 0x7ffff6263888 bool readonly public unsigned QI
        size <integer_cst 0x7ffff610bf48 constant 8>
        unit size <integer_cst 0x7ffff610bf60 constant 1>
        align 8 symtab 0 alias set -1 canonical type 0x7ffff6263888 precision 1
min <integer_cst 0x7ffff612e1b0 0> max <integer_cst 0x7ffff612e1e0 1>>

I think it's still possible to fix this check to handle C++ boolean constants
properly (as if they were literal constants). But for general case we probably
must somehow know (e.g. add a new flag to enum tsubst_flags and pass it to
warn_logical_operator from build_new_op_1), that current expression depends on
template parameter.

[Bug c++/66572] [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66572

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Thu Jul 23 18:57:25 2015
New Revision: 226120

URL: https://gcc.gnu.org/viewcvs?rev=226120&root=gcc&view=rev
Log:
        PR c++/66572
        * pt.c (tsubst_copy_and_build): Add warn_logical_op sentinel.

        * g++.dg/warn/Wlogical-op-2.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/warn/Wlogical-op-2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/66572] [6 Regression] Bogus Wlogical-op warning for operands coming from template instantiations

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66572

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.