[Bug gcov-profile/88924] New: [GCOV] Wrong frequencies when there is complicated if expressions in gcov

[yangyibiao at nju dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88924

            Bug ID: 88924
           Summary: [GCOV] Wrong frequencies when there is complicated if
                    expressions in gcov
           Product: gcc
           Version: 7.3.0
            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/7/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
7.3.0-27ubuntu1~18.04' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-7
--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 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04)

$ cat small.c
int ca[6] = {244, -245, 244, -246, 245, -246};

void main()
{
  for (int i = 0; i < 6; ++i) {
    int flag = i % 2 == 1 && ca[i] != (-2 * i - 1955) >> 3;
    if (flag) {
      ;
    } else if (i % 2 == 0 && ca[i] != (1955 + 2 * i) >> 3) {
      ;
    }
  }

  for (int i = 0; i < 6; ++i) {
    if (i % 2 == 1 && ca[i] != (-2 * i - 1955) >> 3) {
      ;
    } else if (i % 2 == 0 && ca[i] != (1955 + 2 * i) >> 3) {
      ;
    }
  }
}


$ gcc small.c -w --coverage; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:100.00% 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 ca[6] = {244, -245, 244, -246, 245, -246};
        -:    2:
        1:    3:void main()
        -:    4:{
        7:    5:  for (int i = 0; i < 6; ++i) {
        6:    6:    int flag = i % 2 == 1 && ca[i] != (-2 * i - 1955) >> 3;
        6:    7:    if (flag) {
        -:    8:      ;
        6:    9:    } else if (i % 2 == 0 && ca[i] != (1955 + 2 * i) >> 3) {
        -:   10:      ;
        -:   11:    }
        -:   12:  }
        -:   13:
        7:   14:  for (int i = 0; i < 6; ++i) {
        6:   15:    if (i % 2 == 1 && ca[i] != (-2 * i - 1955) >> 3) {
        -:   16:      ;
        3:   17:    } else if (i % 2 == 0 && ca[i] != (1955 + 2 * i) >> 3) {
        -:   18:      ;
        -:   19:    }
        -:   20:  }
        1:   21:}
        -:   22:


Line #17 is wrongly marked as executed 3 times. In fact, this line should be
executed 6 times same to Line #9.