[Bug target/83084] New: [7/8 Regression] -fcompare-debug failure on ppc64le

["trippels at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83084

            Bug ID: 83084
           Summary: [7/8 Regression] -fcompare-debug failure on ppc64le
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
                CC: segher at gcc dot gnu.org
  Target Milestone: ---

On ppc64le:

trippels@gcc2-power8 out % cat v8-stack-trace-impl.ii
enum _Lock_policy { _S_atomic };
template <_Lock_policy = _S_atomic> struct A {
  bool m_fn1();
  int _M_use_count;
};
template <> bool A<>::m_fn1() {
  int a;
  do
    if (a)
      return 0;
  while (__atomic_compare_exchange_n(&_M_use_count, &a, 0, 1, 4, 0));
}

trippels@gcc2-power8 out % g++ --save-temps -fcompare-debug -O2 -c
v8-stack-trace-impl.ii
g++: error: v8-stack-trace-impl.ii: -fcompare-debug failure

trippels@gcc2-power8 out % diff -u v8-stack-trace-impl.gkd
v8-stack-trace-impl.gk.gkd
--- v8-stack-trace-impl.gkd     2017-11-21 06:00:22.288381883 +0000
+++ v8-stack-trace-impl.gk.gkd  2017-11-21 06:00:22.308382369 +0000
@@ -69,16 +69,16 @@
  -> 10)
 (code_label # 0 0 8 (nil) [1 uses])
 (note # 0 0 [bb 5] NOTE_INSN_BASIC_BLOCK)
-(insn:TI # 0 0 (set (mem/v:BLK (scratch:DI) [  A8])
-        (unspec:BLK [
-                (mem/v:BLK (scratch:DI) [  A8])
-            ] UNSPEC_LWSYNC)) "v8-stack-trace-impl.ii":11# {*lwsync}
-     (nil))
 (insn:TI # 0 0 (set (reg:SI 10 10 [138])
         (unspec_volatile:SI [
                 (mem/v:SI (reg/f:DI 3 3 [orig:131 this ] [131]) [  S4 A32])
             ] UNSPECV_LL)) "v8-stack-trace-impl.ii":11# {load_lockedsi}
      (nil))
+(insn:TI # 0 0 (set (mem/v:BLK (scratch:DI) [  A8])
+        (unspec:BLK [
+                (mem/v:BLK (scratch:DI) [  A8])
+            ] UNSPEC_LWSYNC)) "v8-stack-trace-impl.ii":11# {*lwsync}
+     (nil))
 (insn:TI # 0 0 (set (reg:CC 68 0 [141])
         (compare:CC (reg:SI 10 10 [138])
             (const_int 0 [0]))) "v8-stack-trace-impl.ii":11# {*cmpsi_signed}