Re: Fwd: Yet another fix for mcore-sim

[Jeff Law <jeffreyalaw@gmail.com>]

On 12/18/23 05:54, Andrew Burgess wrote:
> Jeff Law <jeffreyalaw@gmail.com> writes:
> 
>> Someday I'll type "sourceware.org" correctly on a consistent basis.
>>
>>
>>
>> -------- Forwarded Message --------
>> Subject: Yet another fix for mcore-sim
>> Date: Sat, 16 Dec 2023 21:52:12 -0700
>> From: Jeff Law <jeffreyalaw@gmail.com>
>> To: gdb-patches@sourcware.org
>>
>>
>> This came up testing the CRC optimization work from Mariam@RAU.
>> Basically to optimize some CRC loops into table lookups or carryless
>> multiplies, we may need to do a bit reflection, which on the mcore
>> processor is done using a rotate instruction.
>>
>> Unfortunately the simulator implementation of rotates has the exact same
>> problem as we saw with right shifts.  The input value may have been sign
>> extended from 32 to 64 bits.  When we rotate the extended value, we get
>> those sign extension bits and thus the wrong result.
>>
>> The fix is the same.  Rather than using a "long", use a uint32_t for the
>> type of the temporary.  This fixes a handful of tests in the GCC testsuite:
>>
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -O0  execution test
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -O1  execution test
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -O2  execution test
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -O2 -flto -fno-use-linker-plugin -flto-partition=none  execution test
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  execution test
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -O3 -g  execution test
>>> mcore-sim: gcc.c-torture/execute/20100805-1.c   -Os  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -O0  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -O1  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -O2  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -O2 -flto -fno-use-linker-plugin -flto-partition=none  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -O3 -g  execution test
>>> mcore-sim: gcc.c-torture/execute/20180112-1.c   -Os  execution test
>>> mcore-sim: gcc.dg/20050922-1.c execution test
>>> mcore-sim: gcc.dg/crc-25.c execution test
>>> mcore-sim: gcc.dg/crc-26.c execution test
>>> mcore-sim: gcc.dg/crc-8.c execution test
>>> mcore-sim: gcc.dg/pr57233.c execution test
>>
>>
>> The crc-* tests are Mariam's CRC optimizer tests.  The rest are
>> regression tests already in the GCC testsuite.
>>
>> OK for the trunk?
> 
> It would be nice if there were some tests added to the simulator tree.
> Could you create one similar to sim/testsuite/mcore/lsr.s maybe?
> 
> (Pre-)Approved with a test:

Test added.  Fix and test pushed to the trunk.

Thanks,
jeff

ps.  Hadn't realized you'd moved to Red Hat.  Looks like we missed each 
other by about ~6 months.