RE: AIX support - Mailing list pgsql-hackers

From: Heikki Linnakangas <hlinnaka@gmail.com>
Date: Wednesday, 19 June 2024 at 8:45 PM
To: Srirama Kucherlapati <sriram.rk@in.ibm.com>, Laurenz Albe <laurenz.albe@cybertec.at>, Bruce Momjian <bruce@momjian.us>, Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Peter Eisentraut <peter@eisentraut.org>, Alvaro Herrera <alvherre@alvh.no-ip.org>, pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>, Noah Misch <noah@leadboat.com>, Michael Paquier <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, Thomas Munro <thomas.munro@gmail.com>, tvk1271@gmail.com <tvk1271@gmail.com>, postgres-ibm-aix@wwpdl.vnet.ibm.com <postgres-ibm-aix@wwpdl.vnet.ibm.com>
Subject: [EXTERNAL] Re: AIX support

On 19/06/2024 17:55, Srirama Kucherlapati wrote:
> +/* Commenting for XLC
> + * "IBM XL C/C++ for AIX, V12.1" miscompiles, for 32-bit, some inline
> + * expansions of ginCompareItemPointers() "long long" arithmetic.  To take
> + * advantage of inlining, build a 64-bit PostgreSQL.
> +#if defined(__ILP32__) && defined(__IBMC__)
> +#define PG_FORCE_DISABLE_INLINE
> +#endif
> + */

This seems irrelevant.

> + * Ordinarily, we'd code the branches here using GNU-style local symbols, that
> + * is "1f" referencing "1:" and so on.  But some people run gcc on AIX with
> + * IBM's assembler as backend, and IBM's assembler doesn't do local symbols.
> + * So hand-code the branch offsets; fortunately, all PPC instructions are
> + * exactly 4 bytes each, so it's not too hard to count.

Could you use GCC assembler to avoid this?

> @@ -662,6 +666,21 @@ tas(volatile slock_t *lock)
> 
>  #if !defined(HAS_TEST_AND_SET)       /* We didn't trigger above, let's try here */
> 
> +#if defined(_AIX)    /* AIX */
> +/*
> + * AIX (POWER)
> + */
> +#define HAS_TEST_AND_SET
> +
> +#include <sys/atomic_op.h>
> +
> +typedef int slock_t;
> +
> +#define TAS(lock)                    _check_lock((slock_t *) (lock), 0, 1)
> +#define S_UNLOCK(lock)               _clear_lock((slock_t *) (lock), 0)
> +#endif        /* _AIX */
> +
> +
>  /* These are in sunstudio_(sparc|x86).s */
> 
>  #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))

What CPI/compiler/OS configuration is this for, exactly? Could we rely
on GCC-provided __sync_lock_test_and_set() builtin function instead?

> +# Allow platforms with buggy compilers to force restrict to not be
> +# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
> +# template.

Surely we don't need that anymore? Or is the compiler still buggy?

Do you still care about 32-bit binaries on AIX? If not, let's make that
the default in configure or a check for it, and remove the instructions
on building 32-bit binaries from the docs.

Please try hard to remove any changes from the diff that are not
absolutely necessary.

- Heikki