Hi Jason: Jason Merrill <[email protected]> 於 2026年8月28日週五 上午2:55寫道： > > On 8/27/26 4:10 AM, Kito Cheng wrote: > > The RISC-V psABI[1] says a function using a standard calling convention > > variant has > > to append an extra ABI tag to its mangled name, following the "ABI tags" > > rule of the Itanium C++ ABI. The only variant listed so far is the > > fixed-length vector calling convention, whose tag is > > riscv_vls_cc_<ABI_VLEN>: > > > > ```c > > __attribute__((riscv_vls_cc(128))) void foo(); > > ``` > > > > now mangles as _Z3fooB16riscv_vls_cc_128v. > > > > The C++ mangler cannot know about target attributes, so we adds a target > > hook, TARGET_CXX_IMPLICIT_ABI_TAGS, that hands back extra tags for a decl. > > > > NOTE: I tried to not adding the new hook by attaching abi_tag attribute, > > however I tried to doing that on TARGET_INSERT_ATTRIBUTES and > > doing some hack way on TARGET_ATTRIBUTE_TABLE during adding calling > > convention attribute, but both are no work well. > > How did that fail? Using TARGET_INSERT_ATTRIBUTES sounds promising to me.
It fails for templates. One key issue is template handling. The ABI tag needs to be added if the `vls_cc` attribute is present. However, the attribute might dropped by `splice_template_attributes` / `is_late_template_attribute`, and `TARGET_INSERT_ATTRIBUTES` is invoked only after that point. Therefore, `TARGET_INSERT_ATTRIBUTES` cannot add the ABI tag correctly. The relevant call flow is roughly: cplus_decl_attributes | |- processing_template_decl? -> splice_template_attributes | # VLS CC attribute may dropped here | |- decl_attributes | |- targetm.insert_attributes | # The VLS CC attribute is no longer visible here | |- save_template_attributes # The VLS CC attribute is restored here I am not very familiar with the C++ front end, especially its template handling, so I may be missing a better way to handle this. Thanks :) > Jason >
