[Bug target/94042] [10 Regression] Bootstrap fails on ppc-linux-gnu

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94042

--- Comment #23 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #20)
> The return value of the first _Z11tsubst_exprP9tree_nodeS0_iS0_b.part.0 was
> being copied into r8 and then copied back into r3 (return value), but not r0
> is used and that r0 is used for mtlr (moving back the return address).

This is the correct explanation, thanks Adrew.

In good version
   │0x104c9128 <._Z19tsubst_template_argP9tree_nodeS0_iS0_+104>     bl     
0x1049f300 <._Z11tsubst_exprP9tree_nodeS0_iS0_b.part.0>

sets return value to $r3, which is then returned ($r8 = $r3, $r3 = $r8):
(gdb) p /x $r3
$60 = 0x3fffaf3814d0

while in bad version we return value of:
   │0x104c9134 <._Z19tsubst_template_argP9tree_nodeS0_iS0_+116>     mtlr    r0
(gdb) p /x $r3
$31 = 0x104c92a4

which is the return address (can be seen in back-trace).