[Bug other/116472] New: Wrong offset format when generating assembly with -S and -masm=intel

[Bug other/116472] New: Wrong offset format when generating assembly with -S and -masm=intel

[8dcc.git at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

            Bug ID: 116472
           Summary: Wrong offset format when generating assembly with -S
                    and -masm=intel
           Product: gcc
           Version: 14.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 8dcc.git at gmail dot com
  Target Milestone: ---

The following C code:

    #include <stdio.h>

    int main(void) {
        int arr[2];
        arr[0] = 123;
        arr[1] = 456;
        printf("%d, %d\n", arr[0], arr[1]);
        return 0;
    }

Is compiled with:

    gcc -S -masm=intel -o output.s source.c

This is a chunk of the generated assembly in output.s:

    ...
    mov QWORD PTR -8[rbp], rax
    xor eax, eax
    mov DWORD PTR -16[rbp], 123
    mov DWORD PTR -12[rbp], 456
    ...

As far as I know, in intel syntax the offset of the effective addresses should
be inside the square brackets, next to the register:

    ...
    mov QWORD PTR [rbp-8], rax
    xor eax, eax
    mov DWORD PTR [rbp-16], 123
    mov DWORD PTR [rbp-12], 456
    ...

---------------------------------------------

My GCC version:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/14.2.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure
--enable-languages=ada,c,c++,d,fortran,go,lto,m2,objc,obj-c++,rust
--enable-bootstrap --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues
--with-build-config=bootstrap-lto --with-linker-hash-style=gnu
--with-system-zlib --enable-__cxa_atexit --enable-cet=auto
--enable-checking=release --enable-clocale=gnu --enable-default-pie
--enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object
--enable-libstdcxx-backtrace --enable-link-serialization=1
--enable-linker-build-id --enable-lto --enable-multilib --enable-plugin
--enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.2.1 20240805 (GCC)

[Bug target/116472] Wrong offset format when generating assembly with -S and -masm=intel

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-08-23
             Status|UNCONFIRMED                 |WAITING

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I can't reproduce this with the trunk nor with GCC 14, I get:
```
main:
.LFB0:
        .cfi_startproc
        lea     ecx, [esp+4]
        .cfi_def_cfa 1, 0
        and     esp, -16
        push    DWORD PTR [ecx-4]
        push    ebp
        mov     ebp, esp
        .cfi_escape 0x10,0x5,0x2,0x75,0
        push    ecx
        .cfi_escape 0xf,0x3,0x75,0x7c,0x6
        sub     esp, 20
        mov     DWORD PTR [ebp-16], 123
        mov     DWORD PTR [ebp-12], 456
        mov     edx, DWORD PTR [ebp-12]
        mov     eax, DWORD PTR [ebp-16]
        sub     esp, 4
        push    edx
        push    eax
        push    OFFSET FLAT:.LC0
        call    printf
        add     esp, 16
        mov     eax, 0
        mov     ecx, DWORD PTR [ebp-4]
        .cfi_def_cfa 1, 0
        leave
        .cfi_restore 5
        lea     esp, [ecx-4]
        .cfi_def_cfa 4, 4
        ret

```

Are you sure you don't have some patch which breaks this?

[Bug target/116472] Wrong offset format when generating assembly with -masm=intel and -fPIE/-fPIC

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Wrong offset format when    |Wrong offset format when
                   |generating assembly with -S |generating assembly with
                   |and -masm=intel             |-masm=intel and -fPIE/-fPIC
             Status|WAITING                     |UNCONFIRMED
     Ever confirmed|1                           |0

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Oh -fPIE is needed to get the "broken" assembly.

[Bug target/116472] Wrong offset format when generating assembly with -masm=intel and -fPIE/-fPIC

[8dcc.git at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

--- Comment #3 from 8dcc.git at gmail dot com ---
> Are you sure you don't have some patch which breaks this?
I haven't manually patched GCC, it was installed it from the Arch repository,
which is apparently configured with `--enable-default-pie`, according to `gcc
-v`.

> Oh -fPIE is needed to get the "broken" assembly.
I tried compiling the source with:

    gcc -S -masm=intel -no-pie -o output.s source.c

And the issue still persists.

[Bug target/116472] Wrong offset format when generating assembly with -masm=intel and -fPIE/-fPIC

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |xry111 at gcc dot gnu.org

--- Comment #4 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to 8dcc.git from comment #3)
> > Are you sure you don't have some patch which breaks this?
> I haven't manually patched GCC, it was installed it from the Arch
> repository, which is apparently configured with `--enable-default-pie`,
> according to `gcc -v`.
> 
> > Oh -fPIE is needed to get the "broken" assembly.
> I tried compiling the source with:
> 
>     gcc -S -masm=intel -no-pie -o output.s source.c
> 
> And the issue still persists.

-no-pie is only passed through to the linker.  The compiler option is -fno-PIE.

[Bug target/116472] Wrong offset format when generating assembly with -masm=intel and -fPIE/-fPIC

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|X86_64                      |x86_64-*-*
   Last reconfirmed|2024-08-23 00:00:00         |2024-08-25
           Keywords|                            |assemble-failure
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed with -fPIE, though gas happily accepts the DWORD PTR -8[rbp] form.

[Bug target/116472] Wrong offset format when generating assembly with -masm=intel and -fPIE/-fPIC

[8dcc.git at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116472

--- Comment #6 from 8dcc.git at gmail dot com ---
(In reply to Xi Ruoyao from comment #4)
> > I tried compiling the source with:
> > 
> >     gcc -S -masm=intel -no-pie -o output.s source.c
> > 
> > And the issue still persists.
> 
> -no-pie is only passed through to the linker.  The compiler option is -fno-PIE.

You are right. And yes, when compiling with -fno-PIE instead of -no-pie, the
issue does not happen.