From: "Mattias Engdegård" <mattias@virtutech.se>
To: gcc@gcc.gnu.org
Subject: Re: Request of new __attribute__ for switch statements (elimination of the bounds check)
Date: Tue, 15 Oct 2002 06:43:00 -0000 [thread overview]
Message-ID: <200210151129.g9FBTIs24008@virtutech.se> (raw)
>There is a value-range-propagation branch that will do it. Comes at a
>considerable cost in compile time though.
VRP, while definitely desirable for other reasons, should not be needed just
for determining that the range test for a fully populated switch can be
skipped. Even stuff like
switch (x & 127) { case 0: ... case 127: ... }
should not need full VRP, or am I mistaken?
Both Sun WorkShop C and Intel C understand this code right away with no extra
hints. Microsoft Visual C needs the hint __assume(0) in the default: branch,
but at least it's possible to eliminate the range test that way.
next reply other threads:[~2002-10-15 11:29 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-15 6:43 Mattias Engdegård [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-10-16 9:19 Robert Dewar
2002-10-15 22:40 Robert Dewar
2002-10-15 23:57 ` Zack Weinberg
2002-10-11 13:22 Robert Dewar
2002-10-11 15:12 ` Kevin Lawton
2002-10-12 10:43 ` Alexandre Oliva
2002-10-11 13:20 Kevin Lawton
2002-10-12 4:18 ` Ralph Loader
2002-10-14 8:31 ` Richard Zidlicky
2002-10-14 10:09 ` Dale Johannesen
2002-10-14 21:11 ` Jamie Lokier
2002-10-14 22:01 ` Zack Weinberg
2002-10-15 8:12 ` Michael Matz
2002-10-15 19:15 ` Zack Weinberg
2002-10-15 19:18 ` Dale Johannesen
2002-10-16 14:07 ` Richard Henderson
2002-10-15 21:16 ` Kevin Lawton
2002-10-15 23:40 ` Tim Hollebeek
2002-10-16 3:40 ` Michael Matz
2002-10-16 13:38 ` Tim Hollebeek
2002-10-16 14:23 ` Michael Matz
2002-10-16 13:27 ` Hartmut Schirmer
2002-10-16 3:25 ` Joseph S. Myers
2002-10-16 7:57 ` Fergus Henderson
2002-10-16 11:19 ` Daniel Jacobowitz
2002-10-15 7:54 ` Michael Matz
2002-10-15 13:29 ` Jamie Lokier
2002-10-15 14:06 ` Kevin Lawton
2002-10-15 15:32 ` Jamie Lokier
2002-10-15 14:28 ` Michael Matz
2002-10-15 15:19 ` Jamie Lokier
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