[Bug ld/25315] `__tcf_0' referenced in section `.rodata._ZNK6common26ChainResidueAtomDescriptor3strB5cxx11Ev.cst4' of mode_query_balls_distances.o: defined in discarded section `.text.__tcf_0[_ZNK6common26ChainResidueAtomDescriptor3strB5cxx11Ev]' of mode_query_balls_dis

[danglin at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25315

--- Comment #12 from John David Anglin <danglin at gcc dot gnu.org> ---
Created attachment 12155
  --> https://sourceware.org/bugzilla/attachment.cgi?id=12155&action=edit
Buggy patch

With the patch, we now get plabels in .rodata comdat sections with same key as
the function.  However, this creates a problem with local references to the
plabel.

        .section       
.text._ZN7Dsymbol8isNspaceEv,"axG",@progbits,_ZN7Dsymbol8isNspaceEv,comdat
        .align 4
        .weak   _ZN7Dsymbol8isNspaceEv
        .type   _ZN7Dsymbol8isNspaceEv, @function
_ZN7Dsymbol8isNspaceEv:
        .PROC
        .CALLINFO FRAME=0,NO_CALLS
        .ENTRY
.LVL12:
.LFB641:
        .loc 2 247 21 is_stmt 1 view -0
        .cfi_startproc
        .loc 2 247 34 view .LVU35
        .loc 2 247 46 is_stmt 0 view .LVU36
        bv %r0(%r2)
        ldi 0,%r28
        .EXIT
        .PROCEND
        .cfi_endproc
.LFE641:
        .size   _ZN7Dsymbol8isNspaceEv, .-_ZN7Dsymbol8isNspaceEv


        .section       
.rodata._ZN7Dsymbol8isNspaceEv,"aG",@progbits,_ZN7Dsymbol8isNspaceEv,comdat
        .align 4
.LC14:
        .word   P%_ZN7Dsymbol8isNspaceEv


        ldil LR'.LC14,%r28
        ldo RR'.LC14(%r28),%r28
        bl __canonicalize_funcptr_for_compare,%r2
.LVL218:
        ldw 0(%r28),%r26


It seems to me that we have to leave the plabel, make sure it's null when it
refers to a discarded function, and suppress the error in ld.  Otherwise, the
linker would need to patch the above sequence into three nop instructions and
a ldi 0,%r28.

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