r6/r7 are not saved/restored when modified only by landing pad entry

[Quuxplusone]

Bugzilla Link	PR27102
Status	RESOLVED FIXED
Importance	P normal
Reported by	Marcin Kościelnicki (koriakin@0x04.net)
Reported on	2016-03-28 18:12:51 -0700
Last modified on	2016-06-28 14:58:57 -0700
Version	trunk
Hardware	Other Linux
CC	kit.barton@gmail.com, llvm-bugs@lists.llvm.org, uweigand@de.ibm.com
Fixed by commit(s)
Attachments	0001-SystemZ-Save-restore-r6-and-r7-if-function-contains-.patch (1860 bytes, text/plain)
Blocks
Blocked by
See also

Created attachment 16106
Proposed patch.

$ cat x.cc
void f();

void g() {
        try {
                f();
        } catch (...) {
        }
}
$ clang --target=s390x-unknown-linux-gnu x.cc -S
$ cat x.s
[...]
stmg    %r11, %r15, 88(%r15)
[...]

Only r11-r15 are saved and restored, despite r6 and r7 being modified by
landing pad entry.  This can result in the function clobbering r6 and r7,
violating the ABI.

Proposed patch attached, but I'm not sure if it's the right place - some
generic code could be a better option, but I couldn't find an easy way to plumb
the register information from TargetLowering.  What do you think?

Found while porting ASan to s390 (breaks throw_catch.cc test).

[Quuxplusone]

Attached 0001-SystemZ-Save-restore-r6-and-r7-if-function-contains-.patch (1860 bytes, text/plain): Proposed patch.

[Quuxplusone]

I have submitted it as http://reviews.llvm.org/D18541