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 <apin...@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.
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
> >
