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?

Jeff