target/6496: Sparc backend clobbers call-return stack of UltraSparc

[davem@redhat.com]

>Number:         6496
>Category:       target
>Synopsis:       Sparc backend clobbers call-return stack of UltraSparc
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 27 23:46:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     davem@redhat.com
>Release:        GCC 3.1 CVS
>Organization:
>Environment:
sparc*-*
>Description:
The Sparc backend peepholes for optimizing a
call followed by a jump should be disabled when
optimizing for UltraSPARC and later.

These optimizations corrupt the call-return stack
so that the end result is slower code not faster code.
>How-To-Repeat:
Compile enclosed testcase with -O2 -mtune=ultrasparc
Look at assembly for "add %o7, OFF, %o7" in delay
slot of calls to 'bar'.
>Fix:
When sparc_pu == PROCESSOR_ULTRASPARC or later, do not
match these peepholes.
>Release-Note:
>Audit-Trail:
>Unformatted:
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