> -----Original Message----- > From: Gcc-patches <gcc-patches- > bounces+jiangning=os.amperecomputing....@gcc.gnu.org> On Behalf Of > Martin Jambor > Sent: Wednesday, June 30, 2021 4:19 AM > To: GCC Patches <gcc-patches@gcc.gnu.org> > Cc: Jan Hubicka <hubi...@ucw.cz> > Subject: [RFC] ipa: Adjust references to identify read-only globals > > Hi, > > this patch has been motivated by SPEC 2017's 544.nab_r in which there is a > static variable which is never written to and so zero throughout the run-time > of the benchmark. However, it is passed by reference to a function in which > it is read and (after some multiplications) passed into __builtin_exp which in > turn unnecessarily consumes almost 10% of the total benchmark run-time.
I do see ~8.5% runtime reduction on aarch64. > The situation is illustrated by the added testcase remref-3.c. > > The patch adds a flag to ipa-prop descriptor of each parameter to mark such > parameters. IPA-CP and inling then take the effort to remove IPA_REF_ADDR > references in the caller and only add IPA_REF_LOAD reference to the > clone/overall inlined function. This is sufficient for subsequent symbol > table > analysis code to identify the read-only variable as such and optimize the > code. > > I plan to compile a number of packages with the patch to test it some more > and get a bit better idea of its impact. But it has passed bootstrap, > LTObootstrap and testing on x86_64-linux and i686-linux and so unless I find > any problem, I would like to commit it at some point next month without any > major changes, so I'd be grateful for any feedback even now. I see 3 cases in SPEC2017 failed to compile on aarch64, i.e. 521.wrf_r, 527.cam4_r, 554.roms_r. For example, pre_step3d.fppized.f90:1260:35: internal compiler error: Segmentation fault 1260 | CALL wclock_on (ng, iNLM, 22) | ^ 0x1645c6b internal_error(char const*, ...) ???:0 0xe1f4f4 place_block_symbol(rtx_def*) ???:0 0x84ab33 use_anchored_address(rtx_def*) ???:0 0x868203 expand_expr_real_1(tree_node*, rtx_def*, machine_mode, expand_modifier, rtx_def**, bool) ???:0 0x868793 expand_expr_real_1(tree_node*, rtx_def*, machine_mode, expand_modifier, rtx_def**, bool) ???:0 0x75b593 expand_call(tree_node*, rtx_def*, int) ???:0 0x86a09f expand_expr_real_1(tree_node*, rtx_def*, machine_mode, expand_modifier, rtx_def**, bool) ???:0 Please submit a full bug report Thanks, -Jiangning