On Thu, Nov 13, 2014 at 4:55 PM, Sandra Loosemore <san...@codesourcery.com> wrote: > This patch to the AArch64 back end adds a couple of additional bics patterns > to match code of the form > > if ((x & y) == x) ...; > > This is testing whether the bits set in x are a subset of the bits set in y; > or, that no bits in x are set that are not set in y. So, it is equivalent > to > > if ((x & ~y) == 0) ...; > > Presently this generates code like > and x21, x21, x20 > cmp x21, x20 > b.eq c0 <main+0xc0> > > and this patch allows it to be written more concisely as: > bics x21, x20, x21 > b.eq c0 <main+0xc0> > > Since the bics instruction sets the condition codes itself, no explicit > comparison is required and the result of the bics computation can be > discarded. > > Regression-tested on aarch64-linux-gnu. OK to commit?
Is this not a duplicate of https://gcc.gnu.org/ml/gcc-patches/2014-11/msg00943.html ? regards Ramana > > -Sandra > > > 2014-11-12 Sandra Loosemore <san...@codesourcery.com> > Chris Jones <chr...@nvidia.com> > > gcc/ > * config/aarch64/aarch64.md (*and<mode>3_compare_op1): New. > (*and<mode>3_compare_op2): New. > > gcc/testsuite/ > * gcc.target/aarch64/bics_3.c: New. > >
