[Bug target/102347] "fatal error: target specific builtin not available" with MMA and LTO

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102347

--- Comment #7 from Peter Bergner <bergner at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #6)
> Quickly looking at the rs6000 code, it fails here:
> 
> #1  0x0000000011a0993c in rs6000_invalid_builtin
> (fncode=MMA_BUILTIN_DISASSEMBLE_ACC_INTERNAL) at
> ../../gcc/config/rs6000/rs6000-call.c:11643
> #2  0x0000000011a13134 in rs6000_builtin_decl (code=1603, initialize_p=true)
> at ../../gcc/config/rs6000/rs6000-call.c:13870
> #3  0x00000000115c3900 in unpack_ts_function_decl_value_fields
> (bp=0x3fffffffe2f0, expr=0x3fffaf195700) at ../../gcc/tree-streamer-in.c:361
> #4  0x00000000115c4790 in streamer_read_tree_bitfields (ib=0x3fffffffe6a0,
> data_in=0x132d1910, expr=0x3fffaf195700) at ../../gcc/tree-streamer-in.c:528
> #5  0x0000000010deaa28 in lto_read_tree_1 (ib=0x3fffffffe6a0,
> data_in=0x132d1910, expr=0x3fffaf195700) at ../../gcc/lto-streamer-in.c:1697
> 
> which relies on rs6000_builtin_mask. Note the mask is set here:
> rs6000_builtin_mask = rs6000_builtin_mask_calculate ();
> 
> where rs6000_builtin_mask_calculate is based on TARGET_* values.

Is that really the issue though?  In a non-lto compile, handle_pragma_target()
ends up calling rs6000_option_override_internal which sets the TARGET_* flags
for the function given the pragma options.  Where does LTO do that?  I think I
see lto read in the default options that were set on the command line, but
where and when does LTO set the options defined by the pragma?  Are they even
streamed out to the fat obj file?  They could be there, but I'm not seeing it.