On 07/02/2017 11:03 AM, Yuri Gribov wrote: > Hi all, > > This is initial patch for > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57371 . Per Joseph's > suggestion it optimizes > (float)lhs CMP rhs > (double)lhs CMP rhs > to > lhs CMP (typeof(x))rhs > whenever typeof(x) can be precisely represented by floating-point type > (e.g. short by float or int by double) and rhs can be precisely > represented by typeof(x). > > Bootstrapped/regtested on x64. Ok for trunk? > > I'd like to extend this further in follow-up patches: > 1) fold always-false/always-true comparisons e.g. > short x; > (float)x > INT16_MAX; // Always false > 2) get rid of cast in comparisons with zero regardless of typeof(lhs) > when -fno-trapping-math: > (float_or_double)lhs CMP 0 > > -Y > > > pr57371-1.patch > > > 2017-07-02 Yury Gribov <tetra2...@gmail.com> > > PR tree-optimization/57371 > * match.pd: New pattern. > * testsuite/gcc.dg/pr57371-1.c: New test. > * testsuite/gcc.dg/pr57371-2.c: New test. > > diff -rupN gcc/gcc/match.pd gcc-57371/gcc/match.pd > --- gcc/gcc/match.pd 2017-06-29 21:14:57.000000000 +0200 > +++ gcc-57371/gcc/match.pd 2017-07-01 09:08:04.000000000 +0200 > @@ -2802,7 +2802,35 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (simplify > (cmp (sq @0) (sq @1)) > (if (! HONOR_NANS (@0)) > - (cmp @0 @1)))))) > + (cmp @0 @1))))) > + > + /* Get rid of float cast in > + (float_type)N CMP M > + if N and M are within the range explicitly representable > + by float type. > + > + TODO: fold always true/false comparisons if M is outside valid range. */ > + (simplify > + (cmp (float @0) REAL_CST@1) > + (if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (@1))) > + (with > + { > + tree itype = TREE_TYPE (@0); > + > + const real_format *fmt = REAL_MODE_FORMAT (TYPE_MODE (TREE_TYPE (@1))); > + > + const REAL_VALUE_TYPE *rhs = TREE_REAL_CST_PTR (@1); > + bool not_rhs_int_p = false; > + wide_int rhs_int = real_to_integer (rhs, ¬_rhs_int_p, > TYPE_PRECISION (itype)); > + } > + (if (!not_rhs_int_p > + && !(TYPE_UNSIGNED (itype) && real_isneg (rhs)) > + && wi::ge_p (rhs_int, wi::min_value (itype), TYPE_SIGN (itype)) > + && wi::le_p (rhs_int, wi::max_value (itype), TYPE_SIGN (itype)) > + && TYPE_PRECISION (itype) <= significand_size (fmt)) > + (cmp @0 { wide_int_to_tree (itype, rhs_int); }) > + )))) > +) Seems like a nit, but instead of "not_rhs_int_p" use "fail" or something like that. That makes it easier to mentally parse the conditional which uses the result.
What happens if @0 is a floating point type? Based on the variable name "itype" and passing TYPE_PRECISION (itype) to real_to_integer, it seems like you're expecting @0 to be an integer. If so, you should verify that it really is an integer type. Seems like a good thing to verify with tests as well. Jeff