From: Tom Lane <tgl@sss.pgh.pa.us>
To: Marina Polyakova <m.polyakova@postgrespro.ru>
cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@postgresql.org,
        Alvaro Herrera <alvherre@alvh.no-ip.org>
Subject: Re: master make check fails on Solaris 10
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Comments: In-reply-to Marina Polyakova <m.polyakova@postgrespro.ru>
	message dated "Mon, 15 Jan 2018 15:07:01 +0300"
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Date: Mon, 15 Jan 2018 18:41:51 -0500
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Marina Polyakova <m.polyakova@postgrespro.ru> writes:
> On 13-01-2018 21:10, Tom Lane wrote:
>> I'm not sure there's much we can do about this.  Dropping the use
>> of the alignment spec isn't a workable option.  If there were a
>> simple way for configure to detect that the compiler generates bad
>> code for that, we could have it do so and reject use of __int128,
>> but it'd be up to you to come up with a workable test.

> I'll think about it..

Attached is a possible test program.  I can confirm it passes on a
machine with working __int128, but I have no idea whether it will
detect the problem on yours.  If not, maybe you can tweak it?

			regards, tom lane


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Content-Type: text/x-c; name="int128test.c"; charset="us-ascii"
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Content-Description: int128test.c

#include <stddef.h>
#include <stdio.h>

/* GCC, Sunpro and XLC support aligned */
#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
#define pg_attribute_aligned(a) __attribute__((aligned(a)))
#endif

typedef __int128 int128a
#if defined(pg_attribute_aligned)
pg_attribute_aligned(8)
#endif
;

/*
 * These are globals to discourage the compiler from folding all the
 * arithmetic tests down to compile-time constants.  We do not have
 * convenient support for 128bit literals at this point...
 */
struct glob128
{
	__int128	start;
	char		pad;
	int128a		a;
	int128a		b;
	int128a		c;
	int128a		d;
} g = {0, 'p', 48828125, 97656255, 0, 0};

int
main()
{
	if (offsetof(struct glob128, a) < 17 ||
		offsetof(struct glob128, a) > 24)
	{
		printf("wrong alignment, %d\n", (int) offsetof(struct glob128, a));
		return 1;
	}
	g.a = (g.a << 12) + 1;		/* 200000000001 */
	g.b = (g.b << 12) + 5;		/* 400000000005 */
	/* use the most relevant arithmetic ops */
	g.c = g.a * g.b;
	g.d = (g.c + g.b) / g.b;
	/* return different values, to prevent optimizations */
	if (g.d != g.a + 1)
	{
		printf("wrong arithmetic result\n");
		return 1;
	}
	printf("A-OK!\n");
	return 0;
}

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