diff options
| author | Peter Klausler <35819229+klausler@users.noreply.github.com> | 2024-03-18 14:11:43 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-03-18 14:11:43 -0700 |
| commit | 0007d7eac9367d184df173a0b7450dfdaaf8a551 (patch) | |
| tree | ee6854510ea132f60d641ba08ffa4060a6da7964 | |
| parent | ea72c082bc29fdceca33f37477b7588f31630a5f (diff) | |
| download | llvm-0007d7eac9367d184df173a0b7450dfdaaf8a551.zip llvm-0007d7eac9367d184df173a0b7450dfdaaf8a551.tar.gz llvm-0007d7eac9367d184df173a0b7450dfdaaf8a551.tar.bz2 | |
[flang] Reduce recursion in common::visit (#85483)
This patch yields small speed-ups in compiler build and execution times,
but more importantly, reduces the stack depth needed in a build
environment where tail call optimization does not appear to occur.
| -rw-r--r-- | flang/include/flang/Common/visit.h | 38 |
1 files changed, 16 insertions, 22 deletions
diff --git a/flang/include/flang/Common/visit.h b/flang/include/flang/Common/visit.h index d3136be..f733b72 100644 --- a/flang/include/flang/Common/visit.h +++ b/flang/include/flang/Common/visit.h @@ -17,27 +17,6 @@ // // Define FLANG_USE_STD_VISIT to avoid this code and make common::visit() an // alias for ::std::visit(). -// -// -// With GCC 9.3.0 on a Haswell x86 Ubuntu system, doing out-of-tree builds: -// Before: -// build: -// 6948.53user 212.48system 27:32.92elapsed 433%CPU -// (0avgtext+0avgdata 6429568maxresident)k -// 36181912inputs+8943720outputs (3613684major+97908699minor)pagefaults 0swaps -// execution of tests: -// 205.99user 26.05system 1:08.87elapsed 336%CPU -// (0avgtext+0avgdata 2671452maxresident)k -// 244432inputs+355464outputs (422major+8746468minor)pagefaults 0swaps -// After: -// build: -// 6651.91user 182.57system 25:15.73elapsed 450%CPU -// (0avgtext+0avgdata 6209296maxresident)k -// 17413480inputs+6376360outputs (1567210major+93068230minor)pagefaults 0swaps -// execution of tests: -// 201.42user 25.91system 1:04.68elapsed 351%CPU -// (0avgtext+0avgdata 2661424maxresident)k -// 238840inputs+295912outputs (428major+8489300minor)pagefaults 0swaps #ifndef FORTRAN_COMMON_VISIT_H_ #define FORTRAN_COMMON_VISIT_H_ @@ -52,7 +31,22 @@ template <std::size_t LOW, std::size_t HIGH, typename RESULT, typename VISITOR, typename... VARIANT> inline RESULT Log2VisitHelper( VISITOR &&visitor, std::size_t which, VARIANT &&...u) { - if constexpr (LOW == HIGH) { + if constexpr (LOW + 7 >= HIGH) { + switch (which - LOW) { +#define VISIT_CASE_N(N) \ + case N: \ + if constexpr (LOW + N <= HIGH) { \ + return visitor(std::get<(LOW + N)>(std::forward<VARIANT>(u))...); \ + } + VISIT_CASE_N(1) + VISIT_CASE_N(2) + VISIT_CASE_N(3) + VISIT_CASE_N(4) + VISIT_CASE_N(5) + VISIT_CASE_N(6) + VISIT_CASE_N(7) +#undef VISIT_CASE_N + } return visitor(std::get<LOW>(std::forward<VARIANT>(u))...); } else { static constexpr std::size_t mid{(HIGH + LOW) / 2}; |