https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89775
Bug ID: 89775
Summary: Stackpointer save/restore instructions optimized away
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: krebbel at gcc dot gnu.org
Target Milestone: ---
Defining the stack pointer register as global register triggers wrong code to
be generated thanks to bug in the prologue/epilogue optimization. In this case
the prologue save instruction for the stack pointer is removed while the
epilogue insn is kept. So r15 will be restored from f0 and hence loaded with
garbage.
register a __asm__("15");
b() { char c = 0; }
b:
ldgr %f2,%r11
lay %r15,-168(%r15)
lgr %r11,%r15
mvi 167(%r11),0
lr 0,0
lgr %r2,%r1
lgdr %r11,%f2
lgdr %r15,%f0
br %r14
Even if a global register is being clobbered in a function we usually do not
save and restore it. However, we still have to do this if it is a special
register. Most of the places in the backend handle this correctly but not the
prologue/epilogue optimization.
A fix is being tested and will be available soon.
