On Thu, 2026-09-24 at 10:21 +1200, best xmg wrote: > Hi all, > > Reference and move semantics are a part of C++ that experienced > engineers > still get subtly wrong, so I audited the tree with clang-tidy's > performance-* checks, which trace whether a by-value parameter is > ever > mutated or a std::move target is actually reachable -- the kind of > exhaustive per-parameter check regular compiler warnings and human > review > aren't built to do. Only patch 1 has a measured performance number; > patches 2-5 are correctness/consistency fixes in the same spirit with > no > individual perf claim. No functional change is intended anywhere in > the > series. > > Patch 1 removes a needless deep-copy of program_state (which owns a > whole > region_model) when -fanalyzer creates an exploded_node, by giving > program_state a move-assignment operator and threading the move > through > point_and_state and exploded_node. > > Testing: > - x86_64-pc-linux-gnu, --enable-languages=c,c++,lto, --disable- > bootstrap. > - check-gcc analyzer.exp/tree-ssa.exp/ipa.exp on current trunk > (492fbdbf99d): 16820+10537 pass. Same 2 pre-existing failures as > unpatched trunk, unrelated to this series: > * omp-parallel-for-1.c: -Wanalyzer-symbol-too-complex depth boundary. > * ssa-sink-18.c: known r17-3756 regression (unrelated ivopts change). > - Timing (patch 1 only): 8 interleaved `cc1 -fanalyzer` runs on > libiberty/cp-demangle.c, binary swapped each run: 63.98s -> 60.10s > median (6.06% faster), no overlap across all 8 pairs.
Thanks, nice to see a measurable performance win in the analyzer for this. Did you try a bootstrap of GCC with the patches? Taking the patches one by one: "[PATCH 1/5] analyzer: avoid deep-copying program_state when creating an exploded_node": looks good to me. "PATCH 2/5] analyzer, diagnostics: add missing std::move for by-value sinks": looks good to me. "[PATCH 3/5] diagnostics: take HTML tag names as const char * in source-printing": looks good to me "[PATCH 4/5] gcc, analyzer: drop std::move calls that have no effect": * the analyzer/*.cc changes look good to me * I can't speak to the gcov.cc change * gcc/text-art/canvas.cc: looks like it would be better to implement an overload of text_art::array2::set that takes an element_t &&, and keep the std::move here, since copying styled_unichar instances is non- trivial * the xml.cc change looks good to me I can't speak to patch 5. Thanks again Dave > > Full test logs and the benchmark script are available on request. > > I don't have push access; posting for review. Happy to split patch 1 > out on its own if that's preferred, or to fold 2-5 together -- > they're > independent of each other and of patch 1. > > The five patches are attached as plain-text files. > > linden (5): > analyzer: avoid deep-copying program_state when creating an > exploded_node > analyzer, diagnostics: add missing std::move for by-value sinks > diagnostics: take HTML tag names as const char * in source-printing > gcc, analyzer: drop std::move calls that have no effect > range-op, tree-ssa-ccp, fold-const, ipa-cp: bind wide_int / > widest_int by > reference > > gcc/analyzer/access-diagram.cc | 2 +- > gcc/analyzer/engine.cc | 17 ++++++++++++----- > gcc/analyzer/exploded-graph.h | 16 ++++++++++++++++ > gcc/analyzer/infinite-loop.cc | 2 +- > gcc/analyzer/program-state.cc | 27 +++++++++++++++++++++++++++ > gcc/analyzer/program-state.h | 1 + > gcc/diagnostics/html-sink.cc | 4 ++-- > gcc/diagnostics/source-printing.cc | 27 ++++++++++++--------------- > gcc/fold-const.cc | 9 +++++---- > gcc/fold-const.h | 8 ++++---- > gcc/gcov.cc | 2 +- > gcc/ipa-cp.cc | 9 ++++++--- > gcc/ipa-cp.h | 6 +++--- > gcc/range-op.cc | 10 +++++----- > gcc/text-art/canvas.cc | 2 +- > gcc/tree-ssa-ccp.cc | 5 +++-- > gcc/xml.cc | 2 +- > 17 files changed, 101 insertions(+), 48 deletions(-) > > Regards, > Linden
