[Bug target/104894] [11/12 Regression] ICE with -fno-plt -mcpu=power10 on PowerPC64 LE Linux

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104894

--- Comment #6 from Alan Modra <amodra at gmail dot com> ---
I'm sorry, I forgot exactly what was happening when I talked about this on the
call.  What I should have said is that -mlongcall code is correct but is
missing a sibcall optimisation.  -fno-plt code (after removing the assert or
using your patch) is incorrect.  A direct call is wrong, because it may require
a plt call stub.  gcc ought to be producing an inline plt call.  Change the
testcase to

void foo();

void bar() {
   foo();
   foo();
}

to see what I mean.  The asm output is

        mflr 0
        std 0,16(1)
        stdu 1,-96(1)
        .cfi_def_cfa_offset 96
        .cfi_offset 65, 16
        pld 12,0(0),1
        .reloc .-8,R_PPC64_PLT_PCREL34_NOTOC,foo
        mtctr 12
        .reloc .-4,R_PPC64_PLTSEQ,foo
        .reloc .,R_PPC64_PLTCALL_NOTOC,foo
        bctrl
        addi 1,1,96
        .cfi_def_cfa_offset 0
        ld 0,16(1)
        mtlr 0
        .cfi_restore 65
        b foo@notoc

That "b foo@notoc" ought to be
        pld 12,0(0),1
        .reloc .-8,R_PPC64_PLT_PCREL34_NOTOC,foo
        mtctr 12
        .reloc .-4,R_PPC64_PLTSEQ,foo
        .reloc .,R_PPC64_PLTCALL_NOTOC,foo
        bctr