[Bug c++/98043] New: (Regression) ICE in verify_gimpl due to bitpacked enum class (amd64)

[Bug c++/98043] New: (Regression) ICE in verify_gimpl due to bitpacked enum class (amd64)

[BenWiederhake.GitHub at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

            Bug ID: 98043
           Summary: (Regression) ICE in verify_gimpl due to bitpacked enum
                    class (amd64)
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: BenWiederhake.GitHub at gmx dot de
  Target Milestone: ---

Created attachment 49640
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49640&action=edit
Preprocessed source code

Compiling the following code crashes g++-10 and g++-11, but not g++-9:

    // g++ -std=c++2a -o /tmp/example.cpp.o -c example.cpp
    enum class MyEnumClass { A };
    struct MyClass {
        MyEnumClass foobar : 8 { MyEnumClass::A };
    };
    bool some_function(MyClass x)
    {
        switch (x.foobar) {
        case MyEnumClass::A:
            return false;
        }
    }

See at the bottom the exact invocation, error messages, and g++ versions.

The enum-class, bit-packing, the seemingly incomplete switch-case, non-constant
switch-argument, all seem to be necessary to trigger the bug.

This bug seems very similar to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97634 , but it's a different
platform. Feel free to merge if it's the same bug.

* What was the outcome of this action?

Compiler crash (error message see below)

* What outcome did you expect instead?

Either a successful compilation, or a compilation error; but not a compiler
crash.


Full error message and versions:

$ /usr/bin/g++-9 --version
g++-9 (Debian 9.3.0-18) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /usr/bin/g++-9 -std=c++2a -o /tmp/example.cpp.o -c example.cpp
example.cpp: In function ‘bool some_function(MyClass)’:
example.cpp:12:1: warning: control reaches end of non-void function [-Wreturn-
type]
   12 | }
      | ^

$ /usr/bin/g++-10 --version
g++-10 (Debian 10.2.0-16) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /usr/bin/g++-10 -std=c++2a -o /tmp/example.cpp.o -c example.cpp
example.cpp: In function ‘bool some_function(MyClass)’:
example.cpp:6:6: error: type precision mismatch in switch statement
    6 | bool some_function(MyClass x)
      |      ^~~~~~~~~~~~~
switch (_1) <default: <D.2095>, case 0: <D.2092>>
example.cpp:6:6: internal compiler error: ‘verify_gimple’ failed
0x128422d verify_gimple_in_seq(gimple*)
        ../../src/gcc/tree-cfg.c:5144
0xf85436 gimplify_body(tree_node*, bool)
        ../../src/gcc/gimplify.c:14888
0xf856a3 gimplify_function_tree(tree_node*)
        ../../src/gcc/gimplify.c:14978
0xdbbe27 cgraph_node::analyze()
        ../../src/gcc/cgraphunit.c:670
0xdbee27 analyze_functions
        ../../src/gcc/cgraphunit.c:1227
0xdbf9f2 symbol_table::finalize_compilation_unit()
        ../../src/gcc/cgraphunit.c:2986
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-10/README.Bugs> for instructions.

$ /usr/lib/gcc-snapshot/bin/g++ --version
g++ (Debian 20201127-1) 11.0.0 20201127 (experimental) [master revision
3493b0c3281:5c47353bc97:5e9f814d754be790aec5b69a95699a8af2654058]
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /usr/lib/gcc-snapshot/bin/g++ -std=c++2a -o /tmp/example.cpp.o -c example.cpp
example.cpp: In function 'bool some_function(MyClass)':
example.cpp:6:6: error: type precision mismatch in switch statement
    6 | bool some_function(MyClass x)
      |      ^~~~~~~~~~~~~
switch (_1) <default: <D.2107>, case 0: <D.2104>>
example.cpp:6:6: internal compiler error: 'verify_gimple' failed
0x12f35bd verify_gimple_in_seq(gimple*)
        ../../src/gcc/tree-cfg.c:5119
0x1006b66 gimplify_body(tree_node*, bool)
        ../../src/gcc/gimplify.c:15329
0x1006ced gimplify_function_tree(tree_node*)
        ../../src/gcc/gimplify.c:15400
0xe37367 cgraph_node::analyze()
        ../../src/gcc/cgraphunit.c:670
0xe39e27 analyze_functions
        ../../src/gcc/cgraphunit.c:1235
0xe3aa1d symbol_table::finalize_compilation_unit()
        ../../src/gcc/cgraphunit.c:2513
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-snapshot/README.Bugs> for instructions.

Downstream ticket:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=976024

Your bugs page says you also want a preprocessed source – I don't see how it's
useful, but sure: Please find attached the preprocessed file "example.ii".

Cheers,
Ben

[Bug c++/98043] (Regression) ICE in verify_gimpl due to bitpacked enum class (amd64)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.0
           Keywords|                            |ice-checking
             Target|                            |x86_64-*-*

[Bug c++/98043] [10/11 Regression] ICE ‘verify_gimple’ failed since r10-5122-g6fcb7ebb377f27c7 since r10-5122-g6fcb7ebb377f27c7

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|(Regression) ICE in         |[10/11 Regression] ICE
                   |verify_gimpl due to         |‘verify_gimple’ failed
                   |bitpacked enum class        |since
                   |(amd64)                     |r10-5122-g6fcb7ebb377f27c7
                   |                            |since
                   |                            |r10-5122-g6fcb7ebb377f27c7
      Known to work|                            |9.3.0
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW
      Known to fail|                            |10.2.0, 11.0
   Last reconfirmed|                            |2020-11-30
     Ever confirmed|0                           |1

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with Jakub's revision.

[Bug c++/98043] [8/9/10/11 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org
            Summary|[10/11 Regression] ICE      |[8/9/10/11 Regression] ICE
                   |‘verify_gimple’ failed      |‘verify_gimple’ failed
                   |since                       |since
                   |r10-5122-g6fcb7ebb377f27c7  |r5-3726-g083e891e69429f93b9
                   |                            |58f6c18e2d52f515bae572

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The ICE is much older is you remove the for the ICE unnecessary C++20
initializer of the bitfield.

enum class B { A };
struct C { B c : 8; };

bool
foo (C x)
{
  switch (x.c)
    {
    case B::A:
      return false;
    default:
      return true;
    }
}

[Bug c++/98043] [8/9/10/11 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

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

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Mine then.

[Bug c++/98043] [8/9/10/11 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.0                        |8.5

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Candidate fix:

--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -3711,6 +3711,10 @@ pop_switch (void)
     SWITCH_STMT_ALL_CASES_P (cs->switch_stmt) = 1;
   if (!cs->break_stmt_seen_p)
     SWITCH_STMT_NO_BREAK_P (cs->switch_stmt) = 1;
+  if (SWITCH_STMT_TYPE (cs->switch_stmt)
+      && SCOPED_ENUM_P (SWITCH_STMT_TYPE (cs->switch_stmt)))
+    SWITCH_STMT_TYPE (cs->switch_stmt)
+      = TREE_TYPE (SWITCH_STMT_COND (cs->switch_stmt));
   gcc_assert (!cs->in_loop_body_p);
   splay_tree_delete (cs->cases);
   switch_stack = switch_stack->next;

[Bug c++/98043] [8/9/10/11 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/98043] [8/9/10/11 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:7482d5a3acb7a8a5564f5cddc4f9d2ebbaea75e4

commit r11-5829-g7482d5a3acb7a8a5564f5cddc4f9d2ebbaea75e4
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Dec 2 10:47:49 2020 -0500

    c++: ICE with switch and scoped enum bit-fields [PR98043]

    In this testcase we are crashing trying to gimplify a switch, because
    the types of the switch condition and case constants have different
    TYPE_PRECISIONs.

    This started with my r5-3726 fix: SWITCH_STMT_TYPE is supposed to be the
    original type of the switch condition before any conversions, so in the
    C++ FE we need to use unlowered_expr_type to get the unlowered type of
    enum bit-fields.

    Normally, the switch type is subject to integral promotions, but here
    we have a scoped enum type and those don't promote:

      enum class B { A };
      struct C { B c : 8; };

      switch (x.c) // type B
        case B::A: // type int, will be converted to B

    Here TREE_TYPE is "signed char" but SWITCH_STMT_TYPE is "B".  When
    gimplifying this in gimplify_switch_expr, the index type is "B" and
    we convert all the case values to "B" in preprocess_case_label_vec,
    but SWITCH_COND is of type "signed char": gimple_switch_index should
    be the (possibly promoted) type, not the original type, so we gimplify
    the "x.c" SWITCH_COND to a SSA_NAME of type "signed char".  And then
    we crash because the precision of the index type doesn't match the
    precision of the case value type.

    I think it makes sense to do the following; at the end of pop_switch
    we've already issued the switch warnings, and since scoped enums don't
    promote, it should be okay to use the type of SWITCH_STMT_COND.  The
    r5-3726 change was about giving warnings for enum bit-fields anyway.

    gcc/cp/ChangeLog:

            PR c++/98043
            * decl.c (pop_switch): If SWITCH_STMT_TYPE is a scoped enum type,
            set it to the type of SWITCH_STMT_COND.

    gcc/testsuite/ChangeLog:

            PR c++/98043
            * g++.dg/cpp0x/enum41.C: New test.

[Bug c++/98043] [8/9/10 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[8/9/10/11 Regression] ICE  |[8/9/10 Regression] ICE
                   |‘verify_gimple’ failed      |‘verify_gimple’ failed
                   |since                       |since
                   |r5-3726-g083e891e69429f93b9 |r5-3726-g083e891e69429f93b9
                   |58f6c18e2d52f515bae572      |58f6c18e2d52f515bae572

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed on trunk thus far.

[Bug c++/98043] [8/9/10 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[BenWiederhake.GitHub at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

--- Comment #7 from Ben Wiederhake <BenWiederhake.GitHub at gmx dot de> ---
A testcase got added in PR 98043. Yay!

The testcase contains a `default:` in the switch-case statement. Wasn't it the
case that the bug got triggered by a *lack* of `default:` case?

[Bug c++/98043] [8/9/10 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Ben Wiederhake from comment #7)
> A testcase got added in PR 98043. Yay!
> 
> The testcase contains a `default:` in the switch-case statement. Wasn't it
> the case that the bug got triggered by a *lack* of `default:` case?

No, it was about a type mismatch between the type of the controlling
expression, and the type of the case value.

Thanks for reporting this issue.

[Bug c++/98043] [8/9/10 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[BenWiederhake.GitHub at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

--- Comment #9 from Ben Wiederhake <BenWiederhake.GitHub at gmx dot de> ---
I totally forgot to say it:

Thanks for fixing it so quickly! :D

When I saw https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97634 I was afraid it
would suffer a slow death – but nope, fixed within a few days. Awesome! Now I
only have to wait for the next release, and my OS's package maintainers. :)

[Bug c++/98043] [8/9/10 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |doko at debian dot org

--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
*** Bug 97634 has been marked as a duplicate of this bug. ***

[Bug c++/98043] [8/9/10 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Marek Polacek
<mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:48aa64322e824d674b955459ea3816f3047629a3

commit r10-9206-g48aa64322e824d674b955459ea3816f3047629a3
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Dec 2 10:47:49 2020 -0500

    c++: ICE with switch and scoped enum bit-fields [PR98043]

    In this testcase we are crashing trying to gimplify a switch, because
    the types of the switch condition and case constants have different
    TYPE_PRECISIONs.

    This started with my r5-3726 fix: SWITCH_STMT_TYPE is supposed to be the
    original type of the switch condition before any conversions, so in the
    C++ FE we need to use unlowered_expr_type to get the unlowered type of
    enum bit-fields.

    Normally, the switch type is subject to integral promotions, but here
    we have a scoped enum type and those don't promote:

      enum class B { A };
      struct C { B c : 8; };

      switch (x.c) // type B
        case B::A: // type int, will be converted to B

    Here TREE_TYPE is "signed char" but SWITCH_STMT_TYPE is "B".  When
    gimplifying this in gimplify_switch_expr, the index type is "B" and
    we convert all the case values to "B" in preprocess_case_label_vec,
    but SWITCH_COND is of type "signed char": gimple_switch_index should
    be the (possibly promoted) type, not the original type, so we gimplify
    the "x.c" SWITCH_COND to a SSA_NAME of type "signed char".  And then
    we crash because the precision of the index type doesn't match the
    precision of the case value type.

    I think it makes sense to do the following; at the end of pop_switch
    we've already issued the switch warnings, and since scoped enums don't
    promote, it should be okay to use the type of SWITCH_STMT_COND.  The
    r5-3726 change was about giving warnings for enum bit-fields anyway.

    gcc/cp/ChangeLog:

            PR c++/98043
            * decl.c (pop_switch): If SWITCH_STMT_TYPE is a scoped enum type,
            set it to the type of SWITCH_STMT_COND.

    gcc/testsuite/ChangeLog:

            PR c++/98043
            * g++.dg/cpp0x/enum41.C: New test.

    (cherry picked from commit 7482d5a3acb7a8a5564f5cddc4f9d2ebbaea75e4)

[Bug c++/98043] [8/9 Regression] ICE ‘verify_gimple’ failed since r5-3726-g083e891e69429f93b958f6c18e2d52f515bae572

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[8/9/10 Regression] ICE     |[8/9 Regression] ICE
                   |‘verify_gimple’ failed      |‘verify_gimple’ failed
                   |since                       |since
                   |r5-3726-g083e891e69429f93b9 |r5-3726-g083e891e69429f93b9
                   |58f6c18e2d52f515bae572      |58f6c18e2d52f515bae572
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #12 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed in GCC 10 too.