From: Ulrich Drepper <drepper@ipd.info.uni-karlsruhe.de>
To: egcs@cygnus.com
Subject: next glibc showstopper
Date: Fri, 21 Nov 1997 21:50:00 -0000 [thread overview]
Message-ID: <x7yb2hpkyb.fsf@myware.rz.uni-karlsruhe.de> (raw)
Hi,
Here's the next problem which prevent successfully compiling the glibc
with the current egcs on ix86:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
double r (double, double);
extern inline int
bar (double x)
{
union { double d; int i[2]; } u = { d: x }; return u.i[1] < 0;
}
int
foo (double d1, double d2)
{
double e = r (d1, d2);
if (bar (d1) && bar (e)) <---- PROBLEM
return 1;
else
return 5;
return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The fault part of the code is this:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
12: e8 fc ff ff ff call 13 <foo+0x13>
17: dd 45 08 fldl 0x8(%ebp)
1a: dd 5d f8 fstpl 0xfffffff8(%ebp)
if (bar (d1) && bar (e))
1d: 83 7d fc 00 cmpl $0x0,0xfffffffc(%ebp)
21: 7d 0d jnl 30 <foo+0x30>
23: dd 5d f8 fstpl 0xfffffff8(%ebp) \ here is something
26: 7d 0a jnl 32 <foo+0x32> / missing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
After the call to `r' (address 12) the return value is in %st(0). The
according to the inline function `d1' is tested. It is copied on the
stack (why?) and the correct word is tested against $0. This is ok.
But now the return value must be checked. Here only the storing
happens but NO compare instruction sets the flags. I.e., the flags as
determined for `d1' are used.
-- Uli
---------------. drepper at gnu.org ,-. Rubensstrasse 5
Ulrich Drepper \ ,-------------------' \ 76149 Karlsruhe/Germany
Cygnus Solutions `--' drepper at cygnus.com `------------------------
next reply other threads:[~1997-11-21 21:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-11-21 21:50 Ulrich Drepper [this message]
1997-12-01 5:20 ` Bernd Schmidt
[not found] <9712012221.AA15274@vlsi1.ultra.nyu.edu>
1997-12-03 5:46 ` Bernd Schmidt
1997-12-06 7:50 ` Jeffrey A Law
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