On Tue, Sep 06, 2011 at 01:11:26AM +0930, Alan Modra wrote:
> Consequently, Mike's change to split rtl for
> indirect calls sometimes sees the scheduler moving the r2 load in the
> indirect call sequence before a toc reference.
Actually, this isn't correct. Mike's change adding rs6000.c
rs6000_call_indirect_aix just made it more likely. Even before this
post-reload scheduling could move the r2 load around, since rs6000.md
call_indirect_aix patterns were (and still are) split post-reload.
Here's an example I was shown today of such damage (qemu compiled
with gcc-4.6-redhat).
.LVL57151:
ld 0,0(31) # load opd+0, function addr
addis 4,2,.LC4758@toc@ha
ld 11,16(31)
mr 7,3
std 2,40(1) # save r2
mr 5,25
addi 4,4,.LC4758@toc@l
mtctr 0 #
mr 6,26
ld 2,8(31) # load opd+8, new toc ptr in r2
mr 3,28
.LBB255670:
.LBB255668:
.loc 8 98 0
addis 27,2,.LC4761@toc@ha # oops, should be using old r2
.LVL57152:
addi 27,27,.LC4761@toc@l
.LBE255668:
.LBE255670:
.loc 3 9212 0
addis 25,2,.LC4762@toc@ha # oops again
.loc 3 9198 0
bctrl # make the call
ld 2,40(1) # restore r2
r27 and r25 set up here for later use now contain bogus values.
The blame rests on my 2011-06-20 change.
--
Alan Modra
Australia Development Lab, IBM
