[Bug target/110611] New: X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[Bug target/110611] New: X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

            Bug ID: 110611
           Summary: X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32
                    code.
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iains at gcc dot gnu.org
  Target Milestone: ---

I've made this target but not sure exactly where it lies - the gimplifier
output looks suspect already - so maybe it's gimplifer/frontend.

this code is distilled from a version of GDB (7.12) where 'bar' is a system
call that breaks with a sign-extended pointer...

the x86 backend sets:
gcc/config/i386/i386.h:#define POINTERS_EXTEND_UNSIGNED 1
which ought, according to gccint mean that pointers get sign-extended...

t.c ====

typedef unsigned long long uint64_t;
typedef uint64_t another_t;
typedef unsigned char byte;

extern void bar (another_t y, another_t z);

void foo (byte *p)
{
   another_t x = (another_t)p;

   bar ((another_t) p, x);
}

===

build : $(compiler) -m32 t.c -S -fdump-tree-gimple -Wall -Wextra

 * If built by the GCC compiler, we get warnings like;
  warning: cast from pointer to integer of different size
[-Wpointer-to-int-cast]
    9 |    another_t x = (another_t)p;

 * if built by G++ we get no warnings

However, in both cases, the generated assembler sign-extends *p => x and the
first arg to bar.

gimple:

void foo (byte * p)
{
  another_t x;

  p.0_1 = (int) p;
  x = (another_t) p.0_1;
  p.1_2 = (int) p;
  _3 = (long long unsigned int) p.1_2;
  bar (_3, x);
}

maybe the combination of 'perhaps wrong' user code, plus the maze of typedefs
is confusing something.

[Bug target/110611] X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-linux-gnu,
                   |                            |x86_64-darwin, i686-darwin
           Keywords|                            |wrong-code
      Known to fail|                            |10.5.0, 14.0

--- Comment #1 from Iain Sandoe <iains at gcc dot gnu.org> ---
Apple GCC-4.2.1 does zero-extend.
I checked back to 5.5 on Darwin the same issue is present to at least then.

[Bug target/110611] X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

--- Comment #2 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Iain Sandoe from comment #0)


> the x86 backend sets:
> gcc/config/i386/i386.h:#define POINTERS_EXTEND_UNSIGNED 1
> which ought, according to gccint mean that pointers get sign-extended...

erm I mean zero-extended:

POINTERS_EXTEND_UNSIGNED [Macro]
A C expression that determines how pointers should be extended from ptr_mode to
either Pmode or word_mode. It is greater than zero if pointers should be
zero-extended, zero if they should be sign-extended, and negative if some other
sort of conversion is needed.

[Bug target/110611] X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

--- Comment #3 from Andreas Schwab <schwab@linux-m68k.org> ---
uint64_t is neither Pmode nor word_mode here.  POINTERS_EXTEND_UNSIGNED is only
relevant if POINTER_SIZE is narrower than Pmode.

[Bug target/110611] X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

--- Comment #4 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Andreas Schwab from comment #3)
> uint64_t is neither Pmode nor word_mode here.  POINTERS_EXTEND_UNSIGNED is
> only relevant if POINTER_SIZE is narrower than Pmode.

So, just pilot-error, then?

[Bug target/110611] X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

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

--- Comment #5 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
You cannot use this internal macro to deduce how your C testcase should behave.
The language standard says this conversion has implementation-defined behavior,
and GCC manual (the user manual, not the internals manual) has a chapter on
implementation-defined behavior, which explicitly says:

https://gcc.gnu.org/onlinedocs/gcc/Arrays-and-pointers-implementation.html

A cast from pointer to integer [...] sign-extends if the pointer representation
is smaller than the integer type [...].

So the behavior is the same for all targets.

[Bug target/110611] X86 is not honouring POINTERS_EXTEND_UNSIGNED in m32 code.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110611

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #6 from Iain Sandoe <iains at gcc dot gnu.org> ---
so just wrong code; OK.