Hi Richard, on 2022/11/23 00:08, Richard Sandiford wrote: > "Kewen.Lin" <li...@linux.ibm.com> writes: >> Hi Richard, >> >> Many thanks for your review comments! >> >>>>> on 2022/8/24 16:17, Kewen.Lin via Gcc-patches wrote: >>>>>> Hi, >>>>>> >>>>>> As discussed in PR98125, -fpatchable-function-entry with >>>>>> SECTION_LINK_ORDER support doesn't work well on powerpc64 >>>>>> ELFv1 because the filled "Symbol" in >>>>>> >>>>>> .section name,"flags"o,@type,Symbol >>>>>> >>>>>> sits in .opd section instead of in the function_section >>>>>> like .text or named .text*. >>>>>> >>>>>> Since we already generates one label LPFE* which sits in >>>>>> function_section of current_function_decl, this patch is >>>>>> to reuse it as the symbol for the linked_to section. It >>>>>> avoids the above ABI specific issue when using the symbol >>>>>> concluded from current_function_decl. >>>>>> >>>>>> Besides, with this support some previous workarounds for >>>>>> powerpc64 ELFv1 can be reverted. >>>>>> >>>>>> btw, rs6000_print_patchable_function_entry can be dropped >>>>>> but there is another rs6000 patch which needs this rs6000 >>>>>> specific hook rs6000_print_patchable_function_entry, not >>>>>> sure which one gets landed first, so just leave it here. >>>>>> >>>>>> Bootstrapped and regtested on below: >>>>>> >>>>>> 1) powerpc64-linux-gnu P8 with default binutils 2.27 >>>>>> and latest binutils 2.39. >>>>>> 2) powerpc64le-linux-gnu P9 (default binutils 2.30). >>>>>> 3) powerpc64le-linux-gnu P10 (default binutils 2.30). >>>>>> 4) x86_64-redhat-linux with default binutils 2.30 >>>>>> and latest binutils 2.39. >>>>>> 5) aarch64-linux-gnu with default binutils 2.30 >>>>>> and latest binutils 2.39. >>>>>> >> >> [snip...] >> >>>>>> diff --git a/gcc/varasm.cc b/gcc/varasm.cc >>>>>> index 4db8506b106..d4de6e164ee 100644 >>>>>> --- a/gcc/varasm.cc >>>>>> +++ b/gcc/varasm.cc >>>>>> @@ -6906,11 +6906,16 @@ default_elf_asm_named_section (const char *name, >>>>>> unsigned int flags, >>>>>> fprintf (asm_out_file, ",%d", flags & SECTION_ENTSIZE); >>>>>> if (flags & SECTION_LINK_ORDER) >>>>>> { >>>>>> - tree id = DECL_ASSEMBLER_NAME (decl); >>>>>> - ultimate_transparent_alias_target (&id); >>>>>> - const char *name = IDENTIFIER_POINTER (id); >>>>>> - name = targetm.strip_name_encoding (name); >>>>>> - fprintf (asm_out_file, ",%s", name); >>>>>> + /* For now, only section "__patchable_function_entries" >>>>>> + adopts flag SECTION_LINK_ORDER, internal label LPFE* >>>>>> + was emitted in default_print_patchable_function_entry, >>>>>> + just place it here for linked_to section. */ >>>>>> + gcc_assert (!strcmp (name, "__patchable_function_entries")); >>> >>> I like the idea of removing the rs600 workaround in favour of making the >>> target-independent more robust. But this seems a bit hackish. What >>> would we do if SECTION_LINK_ORDER was used for something else in future? >>> >> >> Good question! I think it depends on how we can get the symbol for the >> linked_to section, if adopting the name of the decl will suffer the >> similar issue which this patch wants to fix, we have to reuse the label >> LPFE* or some kind of new artificial label in the related section; or >> we can just go with the name of the given decl, or something related to >> that decl. Since we can't predict any future uses, I just placed an >> assertion here to ensure that we would revisit and adjust this part at >> that time. Does it sound reasonable to you? > > Yeah, I guess that's good enough. If the old scheme ends up being > correct for some future use, we can make the new behaviour conditional > on __patchable_function_entries.
Yes, we can check if the given section name is "__patchable_function_entries". > > So yeah, the patch LGTM to me, thanks. Thanks again! I rebased and re-tested it on x86/aarch64/powerpc64{,le}, just committed in r13-4294-gf120196382ac5a. BR, Kewen