[PATCH] Improve match_simplify_replacement in phi-opt
Richard Biener
richard.guenther@gmail.com
Wed Jun 2 07:34:47 GMT 2021
On Wed, Jun 2, 2021 at 9:16 AM Andrew Pinski <pinskia@gmail.com> wrote:
>
> On Tue, Jun 1, 2021 at 11:46 PM Richard Biener via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Tue, Jun 1, 2021 at 9:07 PM apinski--- via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > From: Andrew Pinski <apinski@marvell.com>
> > >
> > > This improves match_simplify_replace in phi-opt to handle the
> > > case where there is one cheap preparation statement in the
> > > middle basic block similar to xor_replacement and others.
> > > This allows to remove xor_replacement too.
> > >
> > > OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
> > >
> > > gcc/ChangeLog:
> > >
> > > PR tree-optimization/25290
> > > * tree-ssa-phiopt.c (xor_replacement): Delete.
> > > (tree_ssa_phiopt_worker): Delete use of xor_replacement.
> > > (match_simplify_replacement): Allow one cheap preparation
> > > statement that can be moved to before the if.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > > * gcc.dg/tree-ssa/pr96928-1.c: Fix testcase for now that ~
> > > happens on the outside of the bit_xor.
> > > ---
> > > gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c | 4 +-
> > > gcc/tree-ssa-phiopt.c | 136 +++++-----------------
> > > 2 files changed, 28 insertions(+), 112 deletions(-)
> > >
> > > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> > > index a2770e5e896..2e86620da11 100644
> > > --- a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> > > +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> > > @@ -1,9 +1,9 @@
> > > /* PR tree-optimization/96928 */
> > > /* { dg-do compile } */
> > > -/* { dg-options "-O2 -fdump-tree-phiopt2" } */
> > > +/* { dg-options "-O2 -fdump-tree-phiopt2 -fdump-tree-optimized" } */
> > > /* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
> > > /* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
> > > -/* { dg-final { scan-tree-dump-times " = ~" 1 "phiopt2" } } */
> > > +/* { dg-final { scan-tree-dump-times " = ~" 1 "optimized" } } */
> > > /* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
> > > /* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
> > >
> > > diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
> > > index 969b868397e..4f98e505029 100644
> > > --- a/gcc/tree-ssa-phiopt.c
> > > +++ b/gcc/tree-ssa-phiopt.c
> > > @@ -63,8 +63,6 @@ static bool minmax_replacement (basic_block, basic_block,
> > > edge, edge, gphi *, tree, tree);
> > > static bool abs_replacement (basic_block, basic_block,
> > > edge, edge, gphi *, tree, tree);
> > > -static bool xor_replacement (basic_block, basic_block,
> > > - edge, edge, gphi *, tree, tree);
> > > static bool spaceship_replacement (basic_block, basic_block,
> > > edge, edge, gphi *, tree, tree);
> > > static bool cond_removal_in_popcount_clz_ctz_pattern (basic_block, basic_block,
> > > @@ -352,9 +350,6 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
> > > cfgchanged = true;
> > > else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> > > cfgchanged = true;
> > > - else if (!early_p
> > > - && xor_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> > > - cfgchanged = true;
> > > else if (!early_p
> > > && cond_removal_in_popcount_clz_ctz_pattern (bb, bb1, e1,
> > > e2, phi, arg0,
> > > @@ -801,9 +796,23 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> > > edge true_edge, false_edge;
> > > gimple_seq seq = NULL;
> > > tree result;
> > > + gimple *stmt_to_move = NULL;
> > >
> > > + /* If the basic block only has a cheap preparation statement. */
> > > if (!empty_block_p (middle_bb))
> > > - return false;
> > > + {
> > > + stmt_to_move = last_and_only_stmt (middle_bb);
> > > + if (!stmt_to_move)
> > > + return false;
> > > + if (gimple_could_trap_p (stmt_to_move)
> > > + || gimple_has_side_effects (stmt_to_move))
> > > + return false;
> >
> > In tree-ssa-ifcombine we in addition check gimple_uses_undefined_value_p ()
> >
> > > + if ((!is_gimple_assign (stmt_to_move)
> > > + || TREE_CODE (gimple_assign_lhs (stmt_to_move)) != SSA_NAME)
> > > + && (!is_gimple_call (stmt_to_move)
> > > + || !gimple_inexpensive_call_p (as_a <gcall *> (stmt_to_move))))
> >
> > any reason to allow calls at this point? ifcombine has
> >
> > /* const calls don't match any of the above, yet they could
> > still have some side-effects - they could contain
> > gimple_could_trap_p statements, like floating point
> > exceptions or integer division by zero. See PR70586.
> > FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
> > should handle this. */
> >
> > and disallows any calls. Not sure if any gimple_inexpensive_call_p could
> > trap for example, at least we don't document that it doesn't (just thinking
> > of IFN_SQRT for example).
>
> I will disallow them then.
>
> >
> > I think we also want to restrict the intermediate stmts to those feeding the
> > PHI in the CFG merge and not allow arbitrary random stmts? Thus sth
> > like
> >
> > tree lhs = gimple_get_lhs (stmt_to_move);
> > if (!lhs || TREE_CODE (lhs) != SSA_NAME || !single_imm_use (...)
> > || use_stmt != phi)
> > return false;
>
> Since this will only be allowing one (assignment) statement, the use
> statement needs to be that phi node at this point due to being used
> with single_non_singleton_phi_for_edges; otherwise you have some kind
> of SSA violation unless there is no usage but that should have already
> been taken care of due to gimple_has_side_effects/gimple_could_trap_p
> I think.
> I will still add the check just in case.
It could be for another PHI node (just thinking of further patches in
the series),
and yes, for stmts w/o a SSA reg LHS (a non-volatile asm with memory output).
Richard.
> Thanks,
> Andrew Pinski
>
> >
> > Richard.
> >
> > > + return false;
> > > + }
> > >
> > > /* Special case A ? B : B as this will always simplify to B. */
> > > if (operand_equal_for_phi_arg_p (arg0, arg1))
> > > @@ -844,7 +853,17 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> > > return false;
> > >
> > > gsi = gsi_last_bb (cond_bb);
> > > -
> > > + if (stmt_to_move)
> > > + {
> > > + if (dump_file && (dump_flags & TDF_DETAILS))
> > > + {
> > > + fprintf (dump_file, "statement un-sinked:\n");
> > > + print_gimple_stmt (dump_file, stmt_to_move, 0,
> > > + TDF_VOPS|TDF_MEMSYMS);
> > > + }
> > > + gimple_stmt_iterator gsi1 = gsi_for_stmt (stmt_to_move);
> > > + gsi_move_before (&gsi1, &gsi);
> > > + }
> > > if (seq)
> > > gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
> > >
> > > @@ -2592,109 +2611,6 @@ abs_replacement (basic_block cond_bb, basic_block middle_bb,
> > > return true;
> > > }
> > >
> > > -/* Optimize x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
> > > -
> > > -static bool
> > > -xor_replacement (basic_block cond_bb, basic_block middle_bb,
> > > - edge e0 ATTRIBUTE_UNUSED, edge e1,
> > > - gphi *phi, tree arg0, tree arg1)
> > > -{
> > > - if (!INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
> > > - return false;
> > > -
> > > - /* OTHER_BLOCK must have only one executable statement which must have the
> > > - form arg0 = ~arg1 or arg1 = ~arg0. */
> > > -
> > > - gimple *assign = last_and_only_stmt (middle_bb);
> > > - /* If we did not find the proper one's complement assignment, then we cannot
> > > - optimize. */
> > > - if (assign == NULL)
> > > - return false;
> > > -
> > > - /* If we got here, then we have found the only executable statement
> > > - in OTHER_BLOCK. If it is anything other than arg = ~arg1 or
> > > - arg1 = ~arg0, then we cannot optimize. */
> > > - if (!is_gimple_assign (assign))
> > > - return false;
> > > -
> > > - if (gimple_assign_rhs_code (assign) != BIT_NOT_EXPR)
> > > - return false;
> > > -
> > > - tree lhs = gimple_assign_lhs (assign);
> > > - tree rhs = gimple_assign_rhs1 (assign);
> > > -
> > > - /* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
> > > - if (!(lhs == arg0 && rhs == arg1) && !(lhs == arg1 && rhs == arg0))
> > > - return false;
> > > -
> > > - gimple *cond = last_stmt (cond_bb);
> > > - tree result = PHI_RESULT (phi);
> > > -
> > > - /* Only relationals comparing arg[01] against zero are interesting. */
> > > - enum tree_code cond_code = gimple_cond_code (cond);
> > > - if (cond_code != LT_EXPR && cond_code != GE_EXPR)
> > > - return false;
> > > -
> > > - /* Make sure the conditional is x OP 0. */
> > > - tree clhs = gimple_cond_lhs (cond);
> > > - if (TREE_CODE (clhs) != SSA_NAME
> > > - || !INTEGRAL_TYPE_P (TREE_TYPE (clhs))
> > > - || TYPE_UNSIGNED (TREE_TYPE (clhs))
> > > - || TYPE_PRECISION (TREE_TYPE (clhs)) != TYPE_PRECISION (TREE_TYPE (arg1))
> > > - || !integer_zerop (gimple_cond_rhs (cond)))
> > > - return false;
> > > -
> > > - /* We need to know which is the true edge and which is the false
> > > - edge so that we know if have xor or inverted xor. */
> > > - edge true_edge, false_edge;
> > > - extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
> > > -
> > > - /* For GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
> > > - will need to invert the result. Similarly for LT_EXPR if
> > > - the false edge goes to OTHER_BLOCK. */
> > > - edge e;
> > > - if (cond_code == GE_EXPR)
> > > - e = true_edge;
> > > - else
> > > - e = false_edge;
> > > -
> > > - bool invert = e->dest == middle_bb;
> > > -
> > > - result = duplicate_ssa_name (result, NULL);
> > > -
> > > - gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
> > > -
> > > - int prec = TYPE_PRECISION (TREE_TYPE (clhs));
> > > - gimple *new_stmt
> > > - = gimple_build_assign (make_ssa_name (TREE_TYPE (clhs)), RSHIFT_EXPR, clhs,
> > > - build_int_cst (integer_type_node, prec - 1));
> > > - gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
> > > -
> > > - if (!useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (clhs)))
> > > - {
> > > - new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
> > > - NOP_EXPR, gimple_assign_lhs (new_stmt));
> > > - gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
> > > - }
> > > - lhs = gimple_assign_lhs (new_stmt);
> > > -
> > > - if (invert)
> > > - {
> > > - new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
> > > - BIT_NOT_EXPR, rhs);
> > > - gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
> > > - rhs = gimple_assign_lhs (new_stmt);
> > > - }
> > > -
> > > - new_stmt = gimple_build_assign (result, BIT_XOR_EXPR, lhs, rhs);
> > > - gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
> > > -
> > > - replace_phi_edge_with_variable (cond_bb, e1, phi, result);
> > > -
> > > - /* Note that we optimized this PHI. */
> > > - return true;
> > > -}
> > > -
> > > /* Auxiliary functions to determine the set of memory accesses which
> > > can't trap because they are preceded by accesses to the same memory
> > > portion. We do that for MEM_REFs, so we only need to track
> > > --
> > > 2.17.1
> > >
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