[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Bug#381970: marked as done (gcc-4.1: [hppa][mips] gcc produces wrong code under -O2)

Your message dated Tue, 8 Aug 2006 12:01:54 +0200
with message-id <20060808100154.GA19042@deprecation.cyrius.com>
and subject line duplicate
has caused the attached Bug report to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what I am
talking about this indicates a serious mail system misconfiguration
somewhere.  Please contact me immediately.)

Debian bug tracking system administrator
(administrator, Debian Bugs database)
--- Begin Message --- 
Package: gcc-4.1
Version: 4.1.1-2
Severity: normal


When trying to solve #374396, we found that gcc with -O2 produces wrong
code in some corner cases in mips and hppa. The problem goes away with
-fno-delayed-brach, but -O0 -fdelayed-branch does not reproduce the
problem. I've tried unsuccessfully to recreate minimally the problem,
but it seems that there are factors governing the optimizations that
I'm not aware.

The problem is in this loop:

	while (cdouble < 0.0)
		cdouble += adouble;

Where cdouble and adouble are doubles (DUH!). It seems that with delayed
branchs, the addition is performed regardless of the result of the test
condition, and when the loop ends, the action is reversed by
substracting. As this is in floation point arithmetic, and the values
are big enough, there is a overflow which is not correctly reversed.

Please see the mentioned bug report for more details. Take into account
that this was causing a FTBFS in perl because it has a LOT of testcases,
but maybe other programs are affected.

--- End Message ---
--- Begin Message --- 
duplicate of:
  #381710: gcc-4.1: wrong code generation for perl on hppa/mips.

-- 
Martin Michlmayr
http://www.cyrius.com/

--- End Message ---
Reply to: