Date: Wed, 12 May 1999 05:43:43 +0400 (MSD)
From: "Dmitry V. Levin" <ldv AT fandra DOT org>
To: PGCC Mailing List <pgcc AT delorie DOT com>
Subject: IA: pgcc-1.1.3 bug?
Message-ID: <Pine.LNX.4.10.9905120539300.22546-300000@LDV.fandra.org>
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Reply-To: pgcc AT delorie DOT com

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--8323328-1517900349-926473423=:22546
Content-Type: TEXT/PLAIN; charset=US-ASCII

Processor: PII-450MHz

Compiler: pgcc-1.1.3 based on egcs-1.1.2 (from RedHat 6.0 SRPMS),
  built with only "-O2" optimization enabled.
  (as it have been said, pgcc-1.1.3 doesn't build with -march=i686)

OS: RedHat-5.2, mostly upgraded to RedHat-6.0 (including glibc-2.1).

Problem: pgcc fails with the following demo code:

int demo_fun( double argument )
{
    if ( 1431655764L < argument )
        return -1;
    return 0;
}

Details:
I've tested this code with argument == 21., changing -march and -O flags.
Result is:
1. Success with -march<i686 (unspecified or 386,486,586), regardless of -O flag:
   "gcc -Wall -g -march=i586 -O6", for example, generates code for demo_fun
   which returns 0;
2. Failure with -march=i686, regardless of -O flag:
   "gcc -Wall -g -march=i686 -O2", for example, generates code for demo_fun
   which returns -1;

3. Comparison of the assembler code generated for demo_fun:
$ gcc -Wall -g -mcpu=i686 -march=i586 -S demo.c -o demo_i586.s
$ gcc -Wall -g -mcpu=i686 -march=i686 -S demo.c -o demo_i686.s
$ diff -u demo_i586.s demo_i686.s
--- demo_i586.s Wed May 12 05:32:20 1999
+++ demo_i686.s Wed May 12 05:32:22 1999
@@ -38,10 +38,11 @@
 .LM2:
        fldl 8(%ebp)
        fldl .LC0
-       fcompp
-       fnstsw %ax
-       andb $69,%ah
-       cmpb $1,%ah
+       fcomip %st(1),%st
+       fstp %st(0)
+       setb %al
+       setp %ah
+       cmpb %al,%ah
        jne .L2
 .stabn 68,0,4,.LM3-demo_fun
 .LM3:
(first works, second not; whole assembler dumps have been attached to this message)

Resume:
  It seems to be pgcc-1.1.3 bug.
  Any feedback would be great.

Regards,
    Dmitry

-------------------------------------------------------------------------------
Dmitry V. Levin         mailto://ldv AT fandra DOT org
Software Engineer       PGP pubkey http://www.fandra.org/users/ldv/pgpkeys.html
Fandra Project          http://www.fandra.org

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