AOS floating point bug

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2 total messages Started by John F Carr Mon, 17 Sep 1990 06:14

#885

Author: John F Carr
Date: Mon, 17 Sep 1990 06:14

33 lines
1531 bytes

There is a bug in the floating point code generator for the 68881
(/usr/lib/libfp.a(f881gen.o)).  In some cases, single precision
floats in general registers can cause bad code generation (register
0 is marked as available for address calculations when it is [1]
not a valid base register for address calculations [2] in use).
Apparently hc doesn't generate much code that triggers this bug,
but gcc does.  This is a fix (it will be making its way though
official channels to IBM as well).


*** /source/bsd-4.3/rt/usr.lib/libfp/genfp/f881gen.c	Fri Jun 16 17:35:44 1989
--- f881gen.c	Mon Sep 17 01:53:39 1990
***************
*** 309,315 ****
  
  if (is_scratchg(gi, (rr & 0x0f)))
  	fp_free_genr(gi, (rr & 0x0f));
! if (is_scratchg(gi, (rr >> 4)))
  	fp_free_genr(gi, (rr >> 4));
  
  return (i);
--- 309,315 ----
  
  if (is_scratchg(gi, (rr & 0x0f)))
  	fp_free_genr(gi, (rr & 0x0f));
! if (is_double(rr) && is_scratchg(gi, (rr >> 4)))
  	fp_free_genr(gi, (rr >> 4));
  
  return (i);

--
    --John Carr (jfc@athena.mit.edu)

Re: AOS floating point bug

#886

Author: brunner
Date: Tue, 18 Sep 1990 17:55

21 lines
1453 bytes

In article <1990Sep17.061429.27757@athena.mit.edu> jfc@athena.mit.edu (John F Carr) writes:
>
>There is a bug in the floating point code generator for the 68881
>(/usr/lib/libfp.a(f881gen.o)).  In some cases, single precision
>floats in general registers can cause bad code generation (register
>0 is marked as available for address calculations when it is [1]
>not a valid base register for address calculations [2] in use).
>Apparently hc doesn't generate much code that triggers this bug,
>but gcc does.  This is a fix (it will be making its way though
>official channels to IBM as well).
>

John,

Thanks for the patch, could you mail me a test case?
Thanks in advance!

#include <std/disclaimer.h>
Eric Brunner, Consultant, IBM AWD Palo Alto	(415) 855-4486
inet: brunner@monet.berkeley.edu		uucp: uunet!ibmsupt!brunner
trying to understand multiprocessing is like having bees live inside your head.

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