Re: [PATCH][PR target/97540] Don't extract memory from operand for normal memory constraint.

[Richard Sandiford <richard.sandiford@arm.com>]

Hongtao Liu via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> On Tue, Oct 27, 2020 at 7:13 PM Richard Sandiford
> <richard.sandiford@arm.com> wrote:
>>
>> Hongtao Liu via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>> > Hi:
>> >   For inline asm, there could be an operand like (not (mem:)), it's
>> > not a valid operand for normal memory constraint.
>> >   Bootstrap is ok, regression test is ok for make check
>> > RUNTESTFLAGS="--target_board='unix{-m32,}'"
>> >
>> > gcc/ChangeLog
>> >         PR target/97540
>> >         * ira.c: (ira_setup_alts): Extract memory from operand only
>> >         for special memory constraint.
>> >         * recog.c (asm_operand_ok): Ditto.
>> >         * lra-constraints.c (process_alt_operands): MEM_P is
>> >         required for normal memory constraint.
>> >
>> > gcc/testsuite/ChangeLog
>> >         * gcc.target/i386/pr97540.c: New test.
>>
>> Sorry to stick my oar in, but I think we should reconsider the
>> bcst_mem_operand approach.  It seems like these patches (and the
>> previous one) are fighting against the principle that operands
>> cannot be arbitrary expressions.
>>
>> This kind of thing was attempted long ago (even before my time!)
>> for SIGN_EXTEND on MIPS.  It ended up causing more problems than
>> it solved and in the end it had to be taken out.  I'm worried that
>> we might end up going through the same cycle again.
>>
>
> Could you provide the thread link for the issue of SIGN_EXTEND on
> MIPS, then I can take a look to see if it's exactly the same issue as
> mine.

I couldn't find anything, sorry.  The patch that finally removed
the MIPS handling was:

  https://gcc.gnu.org/pipermail/gcc-patches/2002-October/088178.html

I know there was some discussion about the problems around then,
but some of it might have been private rather than on-list.
I can't remember the details now.

Thanks,
Richard