Applied to master, thanks! -- Philipp.
On Fri, 10 Jul 2026 at 06:36, Jeffrey Law <[email protected]> wrote: > > > > On 6/16/2026 1:44 AM, Konstantinos Eleftheriou wrote: > > This patch converts the fold-mem-offsets pass from DF to RTL-SSA. > > Along with this conversion, the way the pass collects information > > was completely reworked. Instead of visiting each instruction multiple > > times, this is now done only once. > > > > Most significant changes are: > > * The pass operates mainly on insn_info objects from RTL-SSA. > > * Single iteration over all nondebug INSNs for identification > > of fold-mem-roots. Then walk of the fold-mem-roots' DEF-chain > > to collect foldable constants. > > * The class fold_mem_info holds vectors for the DEF-chain of > > the to-be-folded INSNs (fold_agnostic_insns, which don't need > > to be adjusted, and fold_insns, which need their constant to > > be set to zero). > > * Introduction of a single-USE mode, which only collects DEFs, > > that have a single USE and therefore are safe to transform > > (the fold-mem-root will be the final USE). This mode is fast > > and will always run (unless disabled via -fno-fold-mem-offsets). > > * Introduction of a multi-USE mode, which allows DEFs to have > > multiple USEs, but all USEs must be part of any fold-mem-root's > > DEF-chain. The analysis of all USEs is expensive and therefore, > > this mode is disabled for highly connected CFGs, unless > > -fexpensive-optimizations (enabled by default at -O2) forces it on. > > Note that multi-USE mode will miss some opportunities that the > > single-USE mode finds (e.g. multi-USE mode fails for > > fold-mem-offsets-3.c). > > > > The following testing was done: > > * Bootstrapped and regtested on aarch64-linux, x86-64-linux and > > arm-linux. > > * SPEC CPU tested on aarch64. > > > > A compile time analysis with `/bin/time -v ./install/usr/local/bin/gcc -O2 > > all.i` > > (all.i from PR117922) shows: > > * -fno-fold-mem-offsets: 1681 s (user time) / 23626232 kBytes (max > > resident set size) > > * -ffold-mem-offsets: 1849 s (user time) / 23625708 kBytes (max > > resident set size) > > Multi-USE mode (on by default at -O2 via -fexpensive-optimizations) does > > not have an impact on the duration or the memory footprint. > > > > gcc/ChangeLog: > > > > PR rtl-optimization/117922 > > * fold-mem-offsets.cc (INCLUDE_ALGORITHM): Added definition. > > (INCLUDE_FUNCTIONAL): Likewise. > > (class pass_fold_mem_offsets): Moved to bottom of file. > > (class change_info): New. > > (def_shadowed_by_cond_exec_p): New. > > (get_single_def_in_bb): Converted to RTL-SSA. > > (get_fold_mem_offset_root): Converted to RTL-SSA. > > (get_uses): Removed. > > (fold_offsets): Converted to RTL-SSA. > > (fold_offsets_value): New. > > (fold_offsets_1): Converted to RTL-SSA. > > (has_foldable_uses_p): Converted to RTL-SSA. > > (get_fold_mem_root): Removed. > > (insn_uses_not_in_bitmap): New. > > (drop_unsafe_candidates): New. > > (do_commit_offset): Converted to RTL-SSA. > > (do_analysis): Removed. > > (do_commit_insn): Converted to RTL-SSA. > > (do_fold_info_calculation): Removed. > > (sort_changes): New. > > (struct regno_changes): New. > > (sort_pairs): New. > > (do_check_validity): Removed. > > (get_last_def): New. > > (move_uses_to_prev_def): New. > > (compute_validity_closure): Removed. > > (change_in_vec_p): New. > > (cancel_changes_for_group): New. > > (find_keys_to_remove): New. > > (free_changes_info): New. > > (update_insns): New. > > (fold_mem_offsets_1): New. > > (pass_fold_mem_offsets::execute): Moved to bottom of file. > > (fold_mem_offsets): New. > > > > gcc/testsuite/ChangeLog: > > > > * g++.target/aarch64/fold-mem-offsets.C: New test. > > * gcc.target/aarch64/fold-mem-offsets.c: New test. > > > > Co-authored-by: Christoph Müllner <[email protected]> > OK. Obviously with a change this large there is meaningful chance > something will go wrong. I'll keep my eye on the tester for regressions. > > jeff
