target/2246: Code generated for IA64 doesn't reset NaT bit on scratch reg

[sje at cup dot hp dot com]

>Number:         2246
>Category:       target
>Synopsis:       Code generated for IA64 doesn't reset NaT bit on scratch reg
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 09 14:36:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     sje@cup.hp.com
>Release:        2.97 20010207 (experimental)
>Organization:
>Environment:
IA64 Linux
>Description:
The compiler is using a scratch register after a call in
two successive mix instructions.  This modifies/sets all the
bits of that register but does not reset the NaT bit because
the register is also used as the input to those two mix
instructions.
>How-To-Repeat:
Compile the code with no optimizations on an IA64 system
and examine the resulting assembly code.  After the call to
bar you should see "mix4.l r15 = r15, r16", since r15 is
a scratch register it might have the NaT bit set and this
instruction propogates that NaT bit setting.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="a.c"
Content-Disposition: inline; filename="a.c"

struct s {
	int i;
	int j;
};


struct s foo()
{
	struct s l;
	l.i = 0;
	l.j = 0;
	bar();
	return l;
}