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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Dell.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA0PR19MB4508.namprd19.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: d9f602ba-2f1f-4f81-2ec3-08d9d5fb68fc X-MS-Exchange-CrossTenant-originalarrivaltime: 12 Jan 2022 18:43:22.3876 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 945c199a-83a2-4e80-9f8c-5a91be5752dd X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Y9SR2pUwDFpBmqj+5wSJCFi9fm6frtQn4KGGuQo5x3gHKwys6a/Y5WmwNqyCO8gL5zMHcEISLhLaAajnfo5UJQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR19MB4156 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.425, 18.0.790 definitions=2022-01-12_05:2022-01-11, 2022-01-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 suspectscore=0 spamscore=0 clxscore=1011 adultscore=0 mlxlogscore=999 malwarescore=0 bulkscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201120112 X-Proofpoint-ORIG-GUID: B0xQssBl3X4n_ASwEHsNskPuxFBRkosL X-Proofpoint-GUID: B0xQssBl3X4n_ASwEHsNskPuxFBRkosL X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 spamscore=0 mlxlogscore=999 adultscore=0 phishscore=0 suspectscore=0 mlxscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201120112 X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 Jan 2022 18:43:34 -0000 > On Jan 12, 2022, at 1:13 PM, Hans-Peter Nilsson via Gcc-patches wrote: >=20 >> ... > I recall comments about code quality regressions. Are there > actual numbers? (Preferably from around the transition > time, because I bet targets still supporting "-mlra" have > regressed on the reload side since then.) I haven't looked in a while, but it is certainly the case that the -mlra co= de out of pdp11 is not as good as that coming out of the old reload. My un= derstanding is that LRA isn't as friendly to memory-centric targets like pd= p11 (and vax?). In particular, from what I understood there is no support,= or at least no significant support, for the pre-decrement and post-increme= nt register indirect references that those targets like so much. There was some suggestion along the lines of "please feel free to add it to= LRA" but that's a seriously hairy undertaking for a programmer with no cur= rent knowledge of LRA at all. >>>> people who did porting to LRA. >>> So in theory it might be just pulling the switch for some? That is, >>> removing their definition of TARGET_LRA_P which then defaults >>> to true? >>>=20 >>> Jeff might be able to test this for (all) targets on his harness. >> Given a patch, it's trivial do throw it in and see what the fallout is. >=20 > Again there's talk about LRA and comparing it to CC0, so > again I'll remind of the lack of documentation for LRA (in > contrast to CC0). I'm not just referring to guides to use > for switching over a target to LRA, but sure, that'll help > too. >=20 > For starters, for each constraint and register-class macro > and hook, what's the difference between reload and LRA; > which ones are unused and which ones are new? What I found interesting is that apparently, to first approximation, suppor= ting LRA amounted to "just turn it on". I think there were some issues to = fix in register classes or constraints, more along the lines of "these are = things you should not do for either system but the old reload usually lets = you get away with it". So those were handled by cleaning up the issue in q= uestion generally, not as an LRA-specific change. Compared to CC0 work the effort was vastly smaller, it's a major rewrite of= the back end vs. a few small changes in a few spots. But it's quite possi= ble that the true picture is different and that there should be more change= s. And yes, there really should be documentation saying so. GCCint has tr= aditionally been quite excellent; it would be distressing if the creation o= f new technology like LRA causes it to regress. paul