c++/1687: Extreme compile time regression from 2.95.2

[kelley dot cook at home dot com]

>Number:         1687
>Category:       c++
>Synopsis:       Extreme compile time regression from 2.95.2
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 17 12:06:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Kelley Cook
>Release:        gcc version 2.97 20010115 (experimental)
>Organization:
>Environment:
CYGWIN_NT-5.0 KELLEY 1.1.7(0.31/3/2) 2000-12-25 12:39 i686 unknown
>Description:
This simple program takes has been compiling for well over a day when optimization is enabled.  This is on a 500Mhz PIII.

The same file compilied with optimization under C instead of C++ compiles in under a second.  Ditto for either C or C++ under GCC 2.95.2.

A 16-bit version of the same program, was semi-corrected earlier, but only in the non-optimized version.  See http://gcc.gnu.org/ml/gcc-bugs/2000-08/msg00684.html

That original test case still takes about 1 minute when compiled with -O.  Since a little checking shows that the time approximately doubles with each bit added, I am spectulating that this would take 6 weeks to compile.  A 64 bit version would take a half-billion years.
>How-To-Repeat:
gcc -O mux32.cc
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: unknown; name="mux32.cc"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="mux32.cc"
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