On Thu, 17 Sep 2020 at 13:20, Richard Biener <rguent...@suse.de> wrote: > > This adds the capability to look for available negated multiplications > and divisions, replacing them with cheaper negates. > > Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed. >
This patch caused a regression in fortran, I filed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97109 > 2020-09-17 Richard Biener <rguent...@suse.de> > > * tree-ssa-sccvn.c (visit_nary_op): Value-number multiplications > and divisions to negates of available negated forms. > > * gcc.dg/tree-ssa/ssa-fre-88.c: New testcase. > --- > gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-88.c | 18 +++++++++++ > gcc/tree-ssa-sccvn.c | 35 ++++++++++++++++++++++ > 2 files changed, 53 insertions(+) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-88.c > > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-88.c > b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-88.c > new file mode 100644 > index 00000000000..15d2ca05e65 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-88.c > @@ -0,0 +1,18 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-fre1" } */ > + > +double y[2]; > +void foo (double x) > +{ > + y[0] = x * -3.; > + y[1] = x * 3.; > +} > +void bar (double x, double z) > +{ > + y[0] = -z / x; > + y[1] = z / x; > +} > + > +/* { dg-final { scan-tree-dump-times " \\* " 1 "fre1" } } */ > +/* { dg-final { scan-tree-dump-times " / " 1 "fre1" } } */ > +/* { dg-final { scan-tree-dump-times "= -_" 2 "fre1" } } */ > diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c > index 8fbb1dd46d1..64f1e8c9160 100644 > --- a/gcc/tree-ssa-sccvn.c > +++ b/gcc/tree-ssa-sccvn.c > @@ -4824,6 +4824,40 @@ visit_nary_op (tree lhs, gassign *stmt) > } > } > break; > + case RDIV_EXPR: > + case TRUNC_DIV_EXPR: > + case MULT_EXPR: > + /* Match up ([-]a){/,*}([-])b with v=a{/,*}b, replacing it with -v. */ > + if (! HONOR_SIGN_DEPENDENT_ROUNDING (type)) > + { > + tree rhs[2]; > + rhs[0] = rhs1; > + rhs[1] = gimple_assign_rhs2 (stmt); > + for (unsigned i = 0; i <= 1; ++i) > + { > + unsigned j = i == 0 ? 1 : 0; > + tree ops[2]; > + gimple_match_op match_op (gimple_match_cond::UNCOND, > + NEGATE_EXPR, type, rhs[i]); > + ops[i] = vn_nary_build_or_lookup_1 (&match_op, false); > + ops[j] = rhs[j]; > + if (ops[i] > + && (ops[0] = vn_nary_op_lookup_pieces (2, code, > + type, ops, NULL))) > + { > + gimple_match_op match_op (gimple_match_cond::UNCOND, > + NEGATE_EXPR, type, ops[0]); > + result = vn_nary_build_or_lookup (&match_op); > + if (result) > + { > + bool changed = set_ssa_val_to (lhs, result); > + vn_nary_op_insert_stmt (stmt, result); > + return changed; > + } > + } > + } > + } > + break; > default: > break; > } > @@ -5739,6 +5773,7 @@ eliminate_dom_walker::eliminate_insert (basic_block bb, > if (!stmt > || (!CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt)) > && gimple_assign_rhs_code (stmt) != VIEW_CONVERT_EXPR > + && gimple_assign_rhs_code (stmt) != NEGATE_EXPR > && gimple_assign_rhs_code (stmt) != BIT_FIELD_REF > && (gimple_assign_rhs_code (stmt) != BIT_AND_EXPR > || TREE_CODE (gimple_assign_rhs2 (stmt)) != INTEGER_CST))) > -- > 2.26.2
