| Message ID | DB6PR0801MB2053364EC1B187DD2CF2FBA9834C0@DB6PR0801MB2053.eurprd08.prod.outlook.com |
|---|---|
| State | New |
| Headers | show |
| Series | Canonicalize negates in division | expand |
On Tue, Oct 17, 2017 at 6:30 PM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote: > This patch implements some of the optimizations discussed in > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026. > > Canonicalize x / (- y) into (-x) / y. > > This moves negates out of the RHS of a division in order to > allow further simplifications and potentially more reciprocal CSEs. > > OK for commit? Ok. Richard. > ChangeLog > 2017-10-17 Wilco Dijkstra <wdijkstr@arm.com> > Jackson Woodruff <jackson.woodruff@arm.com> > > gcc/ > PR 71026/tree-optimization > * match.pd: Canonicalize negate in division. > > gcc/testsuite/ > PR 71026/tree-optimization > * gcc.dg/div_neg: New test. > -- > > diff --git a/gcc/match.pd b/gcc/match.pd > index cb48f079b4a310272e49cc319a1b3b0ff2023ba4..ade851f78fb9ac6ce03b752f63e03f3b5a19cda9 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -352,6 +352,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (rdiv @0 (rdiv:s @1 @2)) > (mult (rdiv @0 @1) @2))) > > +/* Simplify x / (- y) to -x / y. */ > +(simplify > + (rdiv @0 (negate @1)) > + (rdiv (negate @0) @1)) > + > (if (flag_unsafe_math_optimizations) > /* Simplify (C / x op 0.0) to x op 0.0 for C > 0. */ > (for op (lt le gt ge) > diff --git a/gcc/testsuite/gcc.dg/div_neg.c b/gcc/testsuite/gcc.dg/div_neg.c > new file mode 100644 > index 0000000000000000000000000000000000000000..da499cda2fba6c943ec99c55cae2ea389f9e1cca > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/div_neg.c > @@ -0,0 +1,10 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-optimized" } */ > + > +float > +div_neg (float x, float y) > +{ > + return (-x / y) * (x / -y); > +} > + > +/* { dg-final { scan-tree-dump-times " / " 1 "optimized" } } */
diff --git a/gcc/match.pd b/gcc/match.pd index cb48f079b4a310272e49cc319a1b3b0ff2023ba4..ade851f78fb9ac6ce03b752f63e03f3b5a19cda9 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -352,6 +352,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (rdiv @0 (rdiv:s @1 @2)) (mult (rdiv @0 @1) @2))) +/* Simplify x / (- y) to -x / y. */ +(simplify + (rdiv @0 (negate @1)) + (rdiv (negate @0) @1)) + (if (flag_unsafe_math_optimizations) /* Simplify (C / x op 0.0) to x op 0.0 for C > 0. */ (for op (lt le gt ge) diff --git a/gcc/testsuite/gcc.dg/div_neg.c b/gcc/testsuite/gcc.dg/div_neg.c new file mode 100644 index 0000000000000000000000000000000000000000..da499cda2fba6c943ec99c55cae2ea389f9e1cca --- /dev/null +++ b/gcc/testsuite/gcc.dg/div_neg.c @@ -0,0 +1,10 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +float +div_neg (float x, float y) +{ + return (-x / y) * (x / -y); +} + +/* { dg-final { scan-tree-dump-times " / " 1 "optimized" } } */
This patch implements some of the optimizations discussed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026. Canonicalize x / (- y) into (-x) / y. This moves negates out of the RHS of a division in order to allow further simplifications and potentially more reciprocal CSEs. OK for commit? ChangeLog 2017-10-17 Wilco Dijkstra <wdijkstr@arm.com> Jackson Woodruff <jackson.woodruff@arm.com> gcc/ PR 71026/tree-optimization * match.pd: Canonicalize negate in division. gcc/testsuite/ PR 71026/tree-optimization * gcc.dg/div_neg: New test. --