middle-end/8306: ICE for bitfield7_y.C in C++ compatibility tests

[janis187@us.ibm.com]

>Number:         8306
>Category:       middle-end
>Synopsis:       ICE for bitfield7_y.C in C++ compatibility tests
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          ice-on-legal-code
>Submitter-Id:   net
>Arrival-Date:   Mon Oct 21 16:46:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Janis Johnson
>Release:        GCC 3.3 20021018 (experimentatal)
>Organization:
>Environment:
powerpc*
>Description:
The testsuite file g++.dg/compat/eh/bitfield7_y.C causes GCC
to ICE for powerpc, arm, and sparc targets (as seen by test
results in the gcc-testresults archive).  These occur with
GCC 3.3 20021018 (experimental).  I don't know if the ICE
occurs with earlier versions of GCC; perhaps someone with
ready access to earlier versions for those targets can try
the test case with them.

The ICE is in simplify_gen_subreg, at simplify-rtx.c:2681.

See David Edelsohn's analysis at
http://gcc.gnu.org/ml/gcc/2002-10/msg01133.html.
>How-To-Repeat:
Compile gcc/testsuite/g++.dg/compat/eh/bitfield7_y.C with
target of powerpc, sparc, or arm.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: