[Bug gcov-profile/114715] New: Gcov allocates branches to wrong row for nested switches

[Bug gcov-profile/114715] New: Gcov allocates branches to wrong row for nested switches

[a_aili at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

            Bug ID: 114715
           Summary: Gcov allocates branches to wrong row for nested
                    switches
           Product: gcc
           Version: 11.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: a_aili at hotmail dot com
  Target Milestone: ---

While using the following GCC version 
gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
11.4.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-11
--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 --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-gcn/usr
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)

gcov allocates branches to the wrong row when using nested switches.
Given the following test program:

#include <stdio.h>

int main()
{
    int a = 1;
    int b = 2;
    int c = -3;
    switch(a)
      {
      case 1:
        c = 3;
        switch(b) {
        case 1:
          c = 4;
          break;
        case 2:
          c = 5;
          break;
        }
        break;
      case 2:
        c = 6;
        break;
      default:
        break;
      }

    printf("%i, %i, %i\n", a, b, c);
}

compiled with 'gcc test.c -o0 --coverage -o test'.
Gcov invoked with 'gcov --branch-count --branch-probabilities test.c' gives


        -:    0:Source:test.c
        -:    0:Graph:test.gcno
        -:    0:Data:test.gcda
        -:    0:Runs:1
        -:    1:#include <stdio.h>
        -:    2:
function main called 1 returned 100% blocks executed 70%
        1:    3:int main()
        -:    4:{
        1:    5:    int a = 1;
        1:    6:    int b = 2;
        1:    7:    int c = -3;
        1:    8:    switch(a)
branch  0 taken 1
branch  1 taken 0
branch  2 taken 0
        -:    9:      {
        1:   10:      case 1:
        1:   11:        c = 3;
branch  0 taken 0
branch  1 taken 1
branch  2 taken 0
        -:   12:        switch(b) {
    #####:   13:        case 1:
    #####:   14:          c = 4;
    #####:   15:          break;
        1:   16:        case 2:
        1:   17:          c = 5;
        1:   18:          break;
        -:   19:        }
        1:   20:        break;
    #####:   21:      case 2:
    #####:   22:        c = 6;
    #####:   23:        break;
    #####:   24:      default:
    #####:   25:        break;
        -:   26:      }
        -:   27:
        1:   28:    printf("%i, %i, %i\n", a, b, c);
call    0 returned 1
        -:   29:}

As you can see the branches for the nested switch is allocated to row 11 and
row 12 is marked as not executed. If gcov should have been consistent on how it
allocates coverage the branches on row 11 should have been allocated correctly
to the switch as on row 8. The second switch on row 12 should also be marked as
executed.

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-04-15
      Known to fail|                            |13.2.0
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  The branches emitted by pass_lower_switch_O0 lack location info,
so does the switch itself, already since at least gimplification.

The GENERIC SWITCH_EXPR has

{file = 0x4926cc0 "/tmp/t.c", line = 12, column = 9, data = 0x0, 
  sysp = false}

we set a location on the BIND we wrap the switch with though.  The outer
switch is not wrapped in a BIND.  That one gets the location from
annotate_all_with_location_after but this function doesn't recurse into
structured gimple.

It's easy to manually set the switch stmt location, annotating random
nested GIMPLE with a location might be odd.  Maybe instead of

  gimple_set_location (bind, EXPR_LOCATION (switch_expr));

we should also set all of the BIND_BODY locations as well?

Jakub, any preference?

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Besides OMP the switch gimplification code is the only one building a new BIND.

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 3df58b962f3..26e96ada4c7 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -3017,6 +3017,7 @@ gimplify_switch_expr (tree *expr_p, gimple_seq *pre_p)

       switch_stmt = gimple_build_switch (SWITCH_COND (switch_expr),
                                         default_case, labels);
+      gimple_set_location (switch_stmt, EXPR_LOCATION (switch_expr));
       /* For the benefit of -Wimplicit-fallthrough, if switch_body_seq
         ends with a GIMPLE_LABEL holding SWITCH_BREAK_LABEL_P LABEL_DECL,
         wrap the GIMPLE_SWITCH up to that GIMPLE_LABEL into a GIMPLE_BIND,

fixes the testcase

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |14.0

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
commit 9d573f71e80e9f6f4aac912fc8fc128aa2697e3a (origin/master, origin/HEAD)
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Apr 15 11:09:17 2024 +0200

    gcov-profile/114715 - missing coverage for switch

    The following avoids missing coverage for the line of a switch statement
    which happens when gimplification emits a BIND_EXPR wrapping the switch
    as that prevents us from setting locations on the containing statements
    via annotate_all_with_location.  Instead set the location of the GIMPLE
    switch directly.

            PR gcov-profile/114715
            * gimplify.cc (gimplify_switch_expr): Set the location of the
            GIMPLE switch.

            * gcc.misc-tests/gcov-24.c: New testcase.

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:5a3cc62dbb45185dd1ca32caec80d57a320ec5a0

commit r13-8682-g5a3cc62dbb45185dd1ca32caec80d57a320ec5a0
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Apr 15 11:09:17 2024 +0200

    gcov-profile/114715 - missing coverage for switch

    The following avoids missing coverage for the line of a switch statement
    which happens when gimplification emits a BIND_EXPR wrapping the switch
    as that prevents us from setting locations on the containing statements
    via annotate_all_with_location.  Instead set the location of the GIMPLE
    switch directly.

            PR gcov-profile/114715
            * gimplify.cc (gimplify_switch_expr): Set the location of the
            GIMPLE switch.

            * gcc.misc-tests/gcov-24.c: New testcase.

    (cherry picked from commit 9d573f71e80e9f6f4aac912fc8fc128aa2697e3a)

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |13.2.1

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for GCC 13+ sofar.  Probably never worked correctly?

[Bug gcov-profile/114715] Gcov allocates branches to wrong row for nested switches

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114715

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:56415e39029012aa3675d3b4b71fb248cf43049e

commit r12-10445-g56415e39029012aa3675d3b4b71fb248cf43049e
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Apr 15 11:09:17 2024 +0200

    gcov-profile/114715 - missing coverage for switch

    The following avoids missing coverage for the line of a switch statement
    which happens when gimplification emits a BIND_EXPR wrapping the switch
    as that prevents us from setting locations on the containing statements
    via annotate_all_with_location.  Instead set the location of the GIMPLE
    switch directly.

            PR gcov-profile/114715
            * gimplify.cc (gimplify_switch_expr): Set the location of the
            GIMPLE switch.

            * gcc.misc-tests/gcov-24.c: New testcase.

    (cherry picked from commit 5a3cc62dbb45185dd1ca32caec80d57a320ec5a0)