On Apr 27, 2023, Alexandre Oliva <ol...@adacore.com> wrote: > On Apr 14, 2023, Alexandre Oliva <ol...@adacore.com> wrote: >> On Mar 23, 2023, Alexandre Oliva <ol...@adacore.com> wrote: >>> This patch introduces infrastructure for targets to add an offset to >>> the label issued after the call_insn to set the call_return_pc >>> attribute. This will be used on rs6000, that sometimes issues another >>> instruction after the call proper as part of a call insn.
>> Ping? >> https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614453.html > Ping? Ping? Refreshed, retested on ppc64le-linux-gnu. Ok to install? Some of the rs6000 call patterns, on some ABIs, issue multiple opcodes out of a single call insn, but the call (bl) or jump (b) is not always the last opcode in the sequence. This does not seem to be a problem for exception handling tables, but the return_pc attribute in the call graph output in dwarf2+ debug information, that takes the address of a label output right after the call, does not match the value of the link register even for non-tail calls. E.g., with ABI_AIX or ABI_ELFv2, such code as: foo (); outputs: bl foo nop LVL#: [...] .8byte .LVL# # DW_AT_call_return_pc but debug info consumers may rely on the return_pc address, and draw incorrect conclusions from its off-by-4 value. This patch uses the infrastructure for targets to add an offset to the label issued after the call_insn to set the call_return_pc attribute, on rs6000, to account for opcodes issued after actual call opcode as part of call insns output patterns. for gcc/ChangeLog * config/rs6000/rs6000.cc (TARGET_CALL_OFFSET_RETURN_LABEL): Override. (rs6000_call_offset_return_label): New. --- gcc/config/rs6000/rs6000.cc | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc index e4dc629ddcc9a..77e6b94a539da 100644 --- a/gcc/config/rs6000/rs6000.cc +++ b/gcc/config/rs6000/rs6000.cc @@ -1779,6 +1779,8 @@ static const scoped_attribute_specs *const rs6000_attribute_table[] = #undef TARGET_OVERLAP_OP_BY_PIECES_P #define TARGET_OVERLAP_OP_BY_PIECES_P hook_bool_void_true +#undef TARGET_CALL_OFFSET_RETURN_LABEL +#define TARGET_CALL_OFFSET_RETURN_LABEL rs6000_call_offset_return_label /* Processor table. */ @@ -14822,6 +14824,22 @@ rs6000_assemble_integer (rtx x, unsigned int size, int aligned_p) return default_assemble_integer (x, size, aligned_p); } +/* Return the offset to be added to the label output after CALL_INSN + to compute the address to be placed in DW_AT_call_return_pc. */ + +static int +rs6000_call_offset_return_label (rtx_insn *call_insn) +{ + /* All rs6000 CALL_INSN output patterns start with a b or bl, always + a 4-byte instruction, but some output patterns issue other + opcodes afterwards. The return label is issued after the entire + call insn, including any such post-call opcodes. Instead of + figuring out which cases need adjustments, we compute the offset + back to the address of the call opcode proper, then add the + constant 4 bytes, to get the address after that opcode. */ + return 4 - get_attr_length (call_insn); +} + /* Return a template string for assembly to emit when making an external call. FUNOP is the call mem argument operand number. */ -- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer More tolerance and less prejudice are key for inclusion and diversity Excluding neuro-others for not behaving ""normal"" is *not* inclusive
