Hmm. I implied there were other regressions, but I just finished scanning them. Shootout-C++/hash2 is the only major one. The others were small, and only at -O0.
> On 2016-Jul-13, at 17:38, Duncan P. N. Exon Smith via cfe-commits > <cfe-commits@lists.llvm.org> wrote: > > We saw mixed results from this on LNT, including some major regressions. For > example, on x86_64, SingleSource/Benchmarks/Shootout-C++/hash2 regressed > 18.5% at -O3 and over 20% at -Os. > > Is this expected? ^ Still interested in an answer, though ;). > >> On 2016-Jul-11, at 15:02, Eric Fiselier via cfe-commits >> <cfe-commits@lists.llvm.org> wrote: >> >> Author: ericwf >> Date: Mon Jul 11 17:02:02 2016 >> New Revision: 275114 >> >> URL: http://llvm.org/viewvc/llvm-project?rev=275114&view=rev >> Log: >> Don't compute modulus of hash if it is smaller than the bucket count. >> >> This cleans up a previous optimization attempt in hash, and results in >> additional performance improvements over that previous attempt. Additionally >> this new optimization does not hinder the power of 2 bucket count >> optimization. >> >> Modified: >> libcxx/trunk/include/__hash_table >> >> Modified: libcxx/trunk/include/__hash_table >> URL: >> http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__hash_table?rev=275114&r1=275113&r2=275114&view=diff >> ============================================================================== >> --- libcxx/trunk/include/__hash_table (original) >> +++ libcxx/trunk/include/__hash_table Mon Jul 11 17:02:02 2016 >> @@ -90,7 +90,8 @@ inline _LIBCPP_INLINE_VISIBILITY >> size_t >> __constrain_hash(size_t __h, size_t __bc) >> { >> - return !(__bc & (__bc - 1)) ? __h & (__bc - 1) : __h % __bc; >> + return !(__bc & (__bc - 1)) ? __h & (__bc - 1) : >> + (__h < __bc ? __h : __h % __bc); >> } >> >> inline _LIBCPP_INLINE_VISIBILITY >> @@ -2201,8 +2202,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc> >> if (__nd != nullptr) >> { >> for (__nd = __nd->__next_; __nd != nullptr && >> - (__hash == __nd->__hash_ >> - || __constrain_hash(__nd->__hash_, __bc) == __chash); >> + __constrain_hash(__nd->__hash_, __bc) == __chash; >> __nd = >> __nd->__next_) >> { >> if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, >> __k)) >> @@ -2231,8 +2231,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc> >> if (__nd != nullptr) >> { >> for (__nd = __nd->__next_; __nd != nullptr && >> - (__hash == __nd->__hash_ >> - || __constrain_hash(__nd->__hash_, __bc) == __chash); >> + __constrain_hash(__nd->__hash_, __bc) == __chash; >> __nd = >> __nd->__next_) >> { >> if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, >> __k)) >> >> >> _______________________________________________ >> cfe-commits mailing list >> cfe-commits@lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits > > _______________________________________________ > cfe-commits mailing list > cfe-commits@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
