On 02/09/2018 05:42 AM, Roger Sayle wrote: > > The following patch implements a number of __builtin_popcount related > optimizations. > (i) popcount(x) == 0 can be simplified to x==0, and popcount(x) != 0 to > x!=0. > (ii) popcount(x&1) can be simplified to x&1, and for unsigned x, > popcount(x>>31) to x>>31. > (iii) popcount (x&6) + popcount(y&16) can be simplified to > popcount((x&6)|(y&16)) > > These may seem obscure transformations, but performing these types of > POPCOUNT > operations are often the performance critical steps in some cheminformatics > applications. > > To implement the above transformations I've introduced the tree_nonzero_bits > function, > which is a tree-level version of rtlanal's nonzero_bits used by the RTL > optimizers. > > The following patch has been tested on x86_64-pc-linux-gnu with a "make > bootstrap" > and "make check" with no regressions, and passes for the four new gcc.dg > test cases. > > Many thanks In advance. Best regards, > > Roger > -- > Roger Sayle, PhD. > NextMove Software Limited > Innovation Centre (Unit 23), Cambridge Science Park, Cambridge, CB4 0EY > > 2018-02-09 Roger Sayle <ro...@nextmovesoftware.com> > > * fold-const.c (tree_nonzero_bits): New function. > * fold-const.h (tree_nonzero_bits): Likewise. > * match.pd (POPCOUNT): New patterns to fold BUILTIN_POPCOUNT and > friends. POPCOUNT(x&1) => x&1, POPCOUNT(x)==0 => x==0, etc. > > 2018-02-09 Roger Sayle <ro...@nextmovesoftware.com> > > * gcc.dg/fold-popcount-1.c: New testcase. > * gcc.dg/fold-popcount-2.c: New testcase. > * gcc.dg/fold-popcount-3.c: New testcase. > * gcc.dg/fold-popcount-4.c: New testcase. Queued for stage1. THanks Roger. I hope things are going well.
jeff
