[Bug gcov-profile/89675] New: [GCOV] A complex statement in while (1) block is wrongly marked as not-executed in gcov

[yangyibiao at nju dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89675

            Bug ID: 89675
           Summary: [GCOV] A complex statement in while (1) block is
                    wrongly marked as not-executed in gcov
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yangyibiao at nju dot edu.cn
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/8/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
8.2.0-1ubuntu2~18.04' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-8
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 8.2.0 (Ubuntu 8.2.0-1ubuntu2~18.04)

$ cat small.c
int foo = 0;
void *bar = 0;
unsigned int baz = 100;

void *pure_alloc ()
{
  void *res;

  while (1)
    {
      res = (void *) ((((unsigned int) (foo + bar))) & ~1);
      foo += 2;
      if (foo < baz)
        return res;
      ;//foo = 0;
    }
}

int main ()
{
  pure_alloc ();
  return 0;
}

$ gcc -O0 --coverage small.c -w; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:87.50% of 8
Creating 'small.c.gcov'

        -:    0:Source:small.c
        -:    0:Graph:small.gcno
        -:    0:Data:small.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:int foo = 0;
        -:    2:void *bar = 0;
        -:    3:unsigned int baz = 100;
        -:    4:
        1:    5:void *pure_alloc ()
        -:    6:{
        -:    7:  void *res;
        -:    8:
        -:    9:  while (1)
        -:   10:    {
    #####:   11:      res = (void *) ((((unsigned int) (foo + bar))) & ~1);
        1:   12:      foo += 2;
        1:   13:      if (foo < baz)
        1:   14:        return res;
        -:   15:      ;//foo = 0;
        -:   16:    }
        -:   17:}
        -:   18:
        1:   19:int main ()
        -:   20:{
        1:   21:  pure_alloc ();
        1:   22:  return 0;
        -:   23:}

Line #11 is wrongly marked as not executed. While Line #15 is not removed, the
coverage result is correct as follows:
$ gcc -O0 --coverage small.c -w; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:88.89% of 9
Creating 'small.c.gcov'

        -:    0:Source:small.c
        -:    0:Graph:small.gcno
        -:    0:Data:small.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:int foo = 0;
        -:    2:void *bar = 0;
        -:    3:unsigned int baz = 100;
        -:    4:
        1:    5:void *pure_alloc ()
        -:    6:{
        -:    7:  void *res;
        -:    8:
        -:    9:  while (1)
        -:   10:    {
       1*:   11:      res = (void *) ((((unsigned int) (foo + bar))) & ~1);
        1:   12:      foo += 2;
        1:   13:      if (foo < baz)
        1:   14:        return res;
    #####:   15:      foo = 0;
        -:   16:    }
        -:   17:}
        -:   18:
        1:   19:int main ()
        -:   20:{
        1:   21:  pure_alloc ();
        1:   22:  return 0;
        -:   23:}