[Bug tree-optimization/103457] New: boolean operations on bit-fields are not merged

[Bug tree-optimization/103457] New: boolean operations on bit-fields are not merged

[roland.illig at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

            Bug ID: 103457
           Summary: boolean operations on bit-fields are not merged
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: roland.illig at gmx dot de
  Target Milestone: ---

~~~c
#include <stdbool.h>

typedef struct GNodeFlagsS {
        bool remake:1;
        bool childMade:1;
        bool force:1;
        bool doneWait:1;
        bool doneOrder:1;
        bool fromDepend:1;
        bool doneAllsrc:1;
        bool cycle:1;
        bool doneCycle:1;
} GNodeFlags;

bool
GNodeFlags_IsNone(GNodeFlags flags)
{
        return !flags.remake
               && !flags.childMade
               && !flags.force
               && !flags.doneWait
               && !flags.doneOrder
               && !flags.fromDepend
               && !flags.doneAllsrc
               && !flags.cycle
               && !flags.doneCycle;
}
~~~

On x86_64, GCC 11.2 generates:

~~~asm
GNodeFlags_IsNone(GNodeFlagsS):
        mov     eax, edi
        and     eax, 1
        jne     .L6
        test    dil, 2
        jne     .L1
        mov     eax, edi
        shr     ax, 2
        and     eax, 1
        jne     .L6
        test    dil, 8
        jne     .L1
        mov     eax, edi
        shr     ax, 4
        and     eax, 1
        jne     .L6
        test    dil, 32
        jne     .L1
        mov     eax, edi
        shr     ax, 6
        and     eax, 1
        jne     .L6
        test    dil, dil
        js      .L1
        shr     di, 8
        mov     eax, edi
        and     eax, 1
        xor     eax, 1
        ret
.L6:
        xor     eax, eax
.L1:
        ret
~~~

ICC 2021.3.0 generates shorter code:

~~~asm
        test      edi, 1                                        #18.10
        jne       ..B1.10       # Prob 50%                      #18.10
        test      edi, 2                                        #19.13
        jne       ..B1.10       # Prob 50%                      #19.13
        test      edi, 4                                        #20.13
        jne       ..B1.10       # Prob 50%                      #20.13
(and so on)
~~~

Many other compilers fail to see the potential for optimizing this code as
well.

Clang is better, it generates:

~~~asm
GNodeFlags_IsNone(GNodeFlagsS):     # @GNodeFlags_IsNone(GNodeFlagsS)
        test    edi, 511
        sete    al
        ret
~~~

[Bug tree-optimization/103457] boolean operations on bit-fields are not merged

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-11-28
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Mine for GCC 13. There is other bugs which are similar too.

[Bug tree-optimization/103457] boolean operations on bit-fields are not merged

[roland.illig at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

--- Comment #2 from Roland Illig <roland.illig at gmx dot de> ---
Cool, thank you for taking this optimization.

Just to give you a bit of background: I discovered this while converting some
of the enum types in BSD Make to proper bitfields, which theoretically should
be possible without affecting the generated code.

https://github.com/NetBSD/src/blob/trunk/usr.bin/make/make.h

It was interesting to play around with this code on https://godbolt.org/,
seeing how differently the available compilers translate this simple code
fragment. That's where the Intel assembler syntax comes from. :)

[Bug tree-optimization/103457] boolean operations on bit-fields are not merged

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org
   Target Milestone|---                         |13.0

[Bug tree-optimization/103457] boolean operations on bit-fields are not merged

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|13.0                        |13.2

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 13.1 is being released, retargeting bugs to GCC 13.2.

[Bug tree-optimization/103457] boolean operations on bit-fields are not merged

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|13.2                        |13.3

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 13.2 is being released, retargeting bugs to GCC 13.3.

[Bug tree-optimization/103457] boolean operations on bit-fields are not merged

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103457

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|13.3                        |13.4

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 13.3 is being released, retargeting bugs to GCC 13.4.