[Bug ipa/62015] New: ipa-cp-clone uses a clone that is too specialized for the call context

[oremanj at mit dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62015

            Bug ID: 62015
           Summary: ipa-cp-clone uses a clone that is too specialized for
                    the call context
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: oremanj at mit dot edu

In the C++ program below, interprocedural constant propagation cloning creates
a clone of A::adjust() specialized for adjust(Side::Invalid, false). This clone
is then used for an adjust(side, false) call when there is no way to prove side
== Side::Invalid. This bug is present in gcc 4.8.2, is not present in 4.7.3,
and is still present in a version compiled from today's SVN. Using an
optimization level less than -O3 or passing -fno-ipa-cp-clone prevents the bug
from manifesting. The onset of the bug was bisected to commit r193410.

$ cat t.cc
extern "C" int printf(const char *fmt, ...);

struct Side {
    enum _Value { Left, Right, Invalid };

    constexpr Side() : _value(Invalid) {}
    constexpr Side(_Value value) : _value(value) {}
    operator _Value() const { return (_Value)_value; }

  private:
    char _value;
};

struct A {
    void init();
    void adjust(Side side, bool final);
    void move(Side side);
};

void A::init()
{
    adjust(Side::Invalid, false);
}

__attribute__((noinline))
void A::adjust(Side side, bool final)
{
    printf("adjust: side is %d, final %d\n", (int)side, final);
}

void A::move(Side side)
{
    printf("move: side is %d\n", (int)side);
    adjust(side, false);
    adjust(side, true);
}

int main()
{
    A t;
    t.move(Side::Left);
}

$ g++49 -v
Using built-in specs.
COLLECT_GCC=g++49
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc49/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local --disable-nls
--libdir=/usr/local/lib/gcc49 --libexecdir=/usr/local/libexec/gcc49
--program-suffix=49 --with-gmp=/usr/local
--with-gxx-include-dir=/usr/local/lib/gcc49/include/c++/
--with-libiconv-prefix=/usr/local --with-system-zlib --disable-rpath
--enable-languages=c,c++ --mandir=/usr/local/man
--infodir=/usr/local/info/gcc49 --disable-initfini-array
--disable-install-libiberty
Thread model: posix
gcc version 4.10.0 20140804 (experimental) (GCC)

$ g++49 -Wall -Wextra -o t t.cc -std=c++11 -O3
$ ./t
move: side is 0
adjust: side is 2, final 0
adjust: side is 0, final 1

The output should be 'side is 0' on all three lines.