https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120203
--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Vineet Gupta <vine...@gcc.gnu.org>: https://gcc.gnu.org/g:fd042192094c456e275c53dfe92383bec1e9fca3 commit r16-1291-gfd042192094c456e275c53dfe92383bec1e9fca3 Author: Vineet Gupta <vine...@rivosinc.com> Date: Sun Jun 8 14:55:11 2025 -0700 RISC-V: frm/mode-switch: robustify call_insn backtracking [PR120203] As described in prior patches of this series, FRM mode switching state machine has special handling around calls. After a call_insn, if in DYN_CALL state, it needs to transition back to DYN, which requires back checking if prev insn was indeed a call. Defering/delaying this could lead to unncessary final transitions leading to extraenous FRM save/restores. However the current back checking of call_insn was too coarse-grained. It used prev_nonnote_nondebug_insn_bb () which implies current insn to be in the same BB as the call_insn, which need not always be true. The problem is not with the API, but the use thereof. Fix this by tracking call_insn more explicitly in TARGET_MODE_NEEDED. - On seeing a call_insn, record a "call note". - On subsequent insns if a "call note" is seen, do the needed state switch and clear the note. - Remove the old BB based search. The number of FRM read/writes across SPEC2017 -Ofast -mrv64gcv improves. Before After ------------- --------------- frrm fsrmi fsrm frrm fsrmi frrm perlbench_r 17 0 1 17 0 1 cpugcc_r 11 0 0 11 0 0 bwaves_r 16 0 1 16 0 1 mcf_r 11 0 0 11 0 0 cactusBSSN_r 19 0 1 19 0 1 namd_r 14 0 1 14 0 1 parest_r 24 0 1 24 0 1 povray_r 26 1 6 26 1 6 lbm_r 6 0 0 6 0 0 omnetpp_r 17 0 1 17 0 1 wrf_r 1268 13 1603 613 13 82 cpuxalan_r 17 0 1 17 0 1 ldecod_r 11 0 0 11 0 0 x264_r 11 0 0 11 0 0 blender_r 61 12 42 39 12 16 cam4_r 45 13 20 40 13 17 deepsjeng_r 11 0 0 11 0 0 imagick_r 132 16 25 33 16 18 leela_r 12 0 0 12 0 0 nab_r 13 0 1 13 0 1 exchange2_r 16 0 1 16 0 1 fotonik3d_r 19 0 1 19 0 1 roms_r 21 0 1 21 0 1 xz_r 6 0 0 6 0 0 ----------------- -------------- 1804 55 1707 1023 55 150 ----------------- -------------- 3566 1228 ----------------- -------------- While this was a missed-optimization exercise, testing exposed a latent bug as additional testsuite failure, captured as PR120203. The existing test float-point-dynamic-frm-74.c was missing FRM save after a call which this fixes (as a side-effect of robust call state tracking). | frrm a5 | fsrmi 1 | | vfadd.vv v1,v8,v9 | fsrm a5 | beq a1,zero,.L2 | | call normalize_vl_1 | frrm a5 | | .L3: | fsrmi 3 | vfadd.vv v8,v8,v9 | fsrm a5 | jr ra | | .L2: | call normalize_vl_2 | frrm a5 <-- missing | j .L3 PR target/120203 gcc/ChangeLog: * config/riscv/riscv.cc (CFUN_IN_CALL): New macro. (struct mode_switching_info): Add new field. (riscv_frm_adjust_mode_after_call): Remove. (riscv_frm_mode_needed): Track call_insn. gcc/testsuite/ChangeLog: * gcc.target/riscv/rvv/base/float-point-dynamic-frm-74.c: Expect an additional FRRM. Signed-off-by: Vineet Gupta <vine...@rivosinc.com>
