optimization/9301: mips-linux gcc 3.2.1 SEGV in try_forward_edges

[cgd@broadcom.com]

>Number:         9301
>Category:       optimization
>Synopsis:       mips-linux gcc 3.2.1 SEGV in try_forward_edges
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          ice-on-legal-code
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 13 15:46:01 PST 2003
>Closed-Date:
>Last-Modified:
>Originator:     Chris Demetriou <cgd@broadcom.com>
>Release:        3.2.1
>Organization:
>Environment:
mips-linux, kernel 2.4.x.
>Description:
mips-linux (native) gcc 3.2.1 ICEs on the following test case.
gdb indicates a SEGV in try_forward_edges.

gcc 3.2.1 from ftp://ftp.gnu.org/pub/gnu/gcc/gcc-3.2.1/gcc-core-3.2.1.tar.gz
built on a mips linux system like:

	tar xvfz gcc-core-3.2.1.tar.gz
	mkdir obj inst
	cd obj
	../gcc-3.2.1/configure --prefix=`pwd`/../inst
	gmake && gmake install

test fails with -O2 or above, but not with -O1 or less.
>How-To-Repeat:
see above.

More info on where it does/doesn't fail:

tried 3.2.1 as a native compiler for x86-linux as well, no
ICE there at up to -O3.

3.2.1 also seems to have the problem on embedded mips targets
(e.g. mipsisa64sb1 8-), but I did not try that
configuration with an unmodified compiler.

a quick test of head-of-trunk with mipsisa32-elf
indicates problem is _not_ present there, but I wouldn't
call my testing comprehensive.  8-)
>Fix:
workaround is to use -O1 or less.  Fix unknown.
>Release-Note:
>Audit-Trail:
>Unformatted:
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