On 7/8/24 11:30 PM, Fei Gao wrote:
On 2024-07-09 01:49 Jeff Law <jeffreya...@gmail.com> wrote:
On 7/8/24 2:39 AM, Fei Gao wrote:
Root cause:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b27d323a368033f0b37e93c57a57a35fd9997864
Commit above tries in targetm.gen_epilogue () to detect if
there's li a0,0 insn at the end of insn chain, if so, cm.popret
is replaced by cm.popretz and li a0,0 insn is deleted.
Insertion of the generated epilogue sequence
into the insn chain doesn't happen at this moment.
If later shrink-wrap decides NOT to insert the epilogue sequence at the end
of insn chain, then the li a0,0 insn has already been mistakeny removed.
Fix this issue by removing generation of cm.popretz in epilogue,
leaving the assignment to a0 and use insn with cm.popret.
That's likely going to result in some kind of code size regression,
but not a correctness regression.
Optimization can be done in future.
Signed-off-by: Fei Gao <gao...@eswincomputing.com>
gcc/ChangeLog:
* config/riscv/riscv.cc (riscv_zcmp_can_use_popretz): Removed.
(riscv_gen_multi_pop_insn): Remove generation of cm.popretz.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/rv32e_zcmp.c: Adapt TC.
* gcc.target/riscv/rv32i_zcmp.c: Likewise.
OK.
Shall I back port this fix to releases/gcc-14?
Yea, that's probably wise given its a correctness issue.
Thanks!
jeff
