[Bug target/72827] [7 Regression] gnat bootstrap broken on powerpc64le-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72827

--- Comment #7 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
It does look possible that this is an LRA issue.  Here's the code right before
failure:

    100dae08:   f8 95 22 39     addi    r9,r2,-27144
    100dae0c:   01 00 40 39     li      r10,1
    100dae10:   00 00 49 99     stb     r10,0(r9)
    100dae14:   b8 04 20 39     li      r9,1208
    100dae18:   14 4a 7f 7c     add     r3,r31,r9
    100dae1c:   08 00 83 e8     ld      r4,8(r3)
    100dae20:   00 00 63 e8     ld      r3,0(r3)
    100dae24:   3d 86 14 48     bl      10223460
<system__secondary_stack__ss_re
lease>
    100dae28:   00 00 00 60     nop

At the call, r3 has a value of 0.  It looks quite possible that the stack load
at 0x100dae20 is from a spill slot.  I don't see offset 1208 used for a
corresponding store anywhere in the function.  There is, however, some odd code
that uses that constant to fiddle with the frame pointer and then set it back
to where it was:

    100da5d8:   b8 04 20 39     li      r9,1208

    100da5e4:   14 4a ff 7f     add     r31,r31,r9
    100da5e8:   50 f8 e9 7f     subf    r31,r9,r31

Whatever's going on there looks like a bug.