From: Torbjorn Granlund <tege@nada.kth.se>
To: law@cygnus.com
Cc: Jim Wilson <wilson@cygnus.com>,
egcs@cygnus.com, "David S. Miller" <davem@jenolan.rutgers.edu>
Subject: Re: This was fun to track down
Date: Sat, 27 Sep 1997 13:40:00 -0000 [thread overview]
Message-ID: <199709272040.WAA16828@squid.pdc.kth.se> (raw)
In-Reply-To: <19356.875168270@hurl.cygnus.com>
Note the following comment in convert_modes; it may apply to any attempt
to use gen_lowpart:
/* There is one case that we must handle specially: If we are converting
a CONST_INT into a mode whose size is twice HOST_BITS_PER_WIDE_INT and
we are to interpret the constant as unsigned, gen_lowpart will do
the wrong if the constant appears negative. What we want to do is
make the high-order word of the constant zero, not all ones. */
An `unsigned' constant that appears negative should never be generated.
Such constants should use const_double.
I think the gen_lowpart code connected to that comment is wrong. When that
code went in, I suggested that the bug in the caller that relied on that
bogus behaviour be fixed instead.
Now gcc's constant representation is ambiguous.
next prev parent reply other threads:[~1997-09-27 13:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-09-22 19:37 David S. Miller
1997-09-23 0:25 ` Jeffrey A Law
1997-09-23 1:49 ` Torbjorn Granlund
1997-09-23 14:09 ` David S. Miller
1997-09-23 13:41 ` Torbjorn Granlund
1997-09-23 13:50 ` David S. Miller
1997-09-23 13:57 ` Torbjorn Granlund
1997-09-23 14:16 ` David S. Miller
1997-09-23 19:05 ` Jeffrey A Law
1997-09-24 12:58 ` Jim Wilson
1997-09-24 23:15 ` Jeffrey A Law
1997-09-27 13:40 ` Torbjorn Granlund [this message]
1997-09-27 23:38 ` Jeffrey A Law
1997-09-29 11:53 ` Jim Wilson
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