On Tue, Oct 17, 2017 at 6:32 PM, Wilco Dijkstra <wilco.dijks...@arm.com> wrote: > This patch implements some of the optimizations discussed in > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026. > > Canonicalize x / (C1 * y) into (x * C2) / y. > > This moves constant multiplies out of the RHS of a division in order > to allow further simplifications (such as (C1 * x) / (C2 * y) -> > (C3 * x) / y) and to enable more reciprocal CSEs. > > OK for commit? > > ChangeLog > 2017-10-17 Wilco Dijkstra <wdijk...@arm.com> > Jackson Woodruff <jackson.woodr...@arm.com> > > gcc/ > PR 71026/tree-optimization > * match.pd: Canonicalize constant multiplies in division. > > gcc/testsuite/ > PR 71026/tree-optimization > * gcc.dg/cse_recip.c: New test. > -- > > diff --git a/gcc/match.pd b/gcc/match.pd > index > ade851f78fb9ac6ce03b752f63e03f3b5a19cda9..532fabf51ce8a45d54147a3ae0b3917e22b1a4d0 > 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -342,10 +342,20 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (negate @0))) > > (if (flag_reciprocal_math) > - /* Convert (A/B)/C to A/(B*C) */ > + /* Convert (A/B)/C to A/(B*C). */ > (simplify > (rdiv (rdiv:s @0 @1) @2) > - (rdiv @0 (mult @1 @2))) > + (rdiv @0 (mult @1 @2))) > + > + /* Canonicalize x / (C1 * y) to (x * C2) / y. */ > + (if (optimize)
why if (optimize) here? The pattern you removed has no such check. As discussed this may undo CSE of C1 * y so please check for a single-use on the mult with :s > + (simplify > + (rdiv @0 (mult @1 REAL_CST@2)) > + (if (!real_zerop (@1)) why this check? The pattern below didn't have it. Richard. > + (with > + { tree tem = const_binop (RDIV_EXPR, type, build_one_cst (type), @2); } > + (if (tem) > + (rdiv (mult @0 { tem; } ) @1)))))) > > /* Convert A/(B/C) to (A/B)*C */ > (simplify > @@ -628,15 +638,6 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (if (tem) > (rdiv { tem; } @1))))) > > -/* Convert C1/(X*C2) into (C1/C2)/X */ > -(simplify > - (rdiv REAL_CST@0 (mult @1 REAL_CST@2)) > - (if (flag_reciprocal_math) > - (with > - { tree tem = const_binop (RDIV_EXPR, type, @0, @2); } > - (if (tem) > - (rdiv { tem; } @1))))) > - > /* Simplify ~X & X as zero. */ > (simplify > (bit_and:c (convert? @0) (convert? (bit_not @0))) > diff --git a/gcc/testsuite/gcc.dg/cse_recip.c > b/gcc/testsuite/gcc.dg/cse_recip.c > new file mode 100644 > index > 0000000000000000000000000000000000000000..20ed529c33ebecc911fb540a8b2b597bba0023e6 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/cse_recip.c > @@ -0,0 +1,12 @@ > +/* { dg-do compile } */ > +/* { dg-options "-Ofast -fdump-tree-optimized" } */ > + > +void > +cse_recip (float x, float y, float *a) > +{ > + a[0] = y / (5 * x); > + a[1] = y / (3 * x); > + a[2] = y / x; > +} > + > +/* { dg-final { scan-tree-dump-times " / " 1 "optimized" } } */ >