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unswitch: Replace manual ondemand maybe_undef with ssa_name_maybe_undef_p/mark_ssa_maybe_undefs [PR116848]

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The ondemand maybe_undef that follows phis was added in r7-6427-g8b670f93ab1136
but then later ssa_name_maybe_undef_p/mark_ssa_maybe_undefs was added in
r13-972-gbe2861fe8c527a. This moves the ondemand one to use
mark_ssa_maybe_undefs/ssa_name_maybe_undef_p instead. Which itself will be
faster since the mark_ssa_maybe_undefs is a walk based on the uses of
undefined names (and only once) rather than a walk based on the def of
ones which are more likely defined (and on demand).

Even though the ondemand maybe_undef had some extra special cases, those won't make
a big difference in most code.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/116848

gcc/ChangeLog:

	* tree-ssa-loop-unswitch.cc (tree_ssa_unswitch_loops): Call mark_ssa_maybe_undefs.
	(is_maybe_undefined): Call ssa_name_maybe_undef_p instead of ondemand undef.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
This commit is contained in:
Andrew Pinski 2024-09-26 05:55:58 +00:00
parent 1a0b33ebc5
commit 9c04112fdc
1 changed files with 2 additions and 59 deletions
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61
gcc/tree-ssa-loop-unswitch.cc
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@ -329,6 +329,7 @@ tree_ssa_unswitch_loops (function *fun)
bool changed_unswitch = false;
bool changed_hoist = false;
auto_edge_flag ignored_edge_flag (fun);
mark_ssa_maybe_undefs ();
ranger = enable_ranger (fun);
@ -427,65 +428,7 @@ is_maybe_undefined (const tree name, gimple *stmt, class loop *loop)
if (gimple_bb (stmt) == loop->header)
return false;
auto_bitmap visited_ssa;
auto_vec<tree> worklist;
worklist.safe_push (name);
bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (name));
while (!worklist.is_empty ())
{
tree t = worklist.pop ();
/* If it's obviously undefined, avoid further computations. */
if (ssa_undefined_value_p (t, true))
return true;
if (ssa_defined_default_def_p (t))
continue;
gimple *def = SSA_NAME_DEF_STMT (t);
/* Check that all the PHI args are fully defined. */
if (gphi *phi = dyn_cast <gphi *> (def))
{
for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
{
tree t = gimple_phi_arg_def (phi, i);
/* If an SSA has already been seen, it may be a loop,
but we can continue and ignore this use. Otherwise,
add the SSA_NAME to the queue and visit it later. */
if (TREE_CODE (t) == SSA_NAME
&& bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t)))
worklist.safe_push (t);
}
continue;
}
/* Uses in stmts always executed when the region header executes
are fine. */
if (dominated_by_p (CDI_DOMINATORS, loop->header, gimple_bb (def)))
continue;
/* Handle calls and memory loads conservatively. */
if (!is_gimple_assign (def)
|| (gimple_assign_single_p (def)
&& gimple_vuse (def)))
return true;
/* Check that any SSA names used to define NAME are also fully
defined. */
use_operand_p use_p;
ssa_op_iter iter;
FOR_EACH_SSA_USE_OPERAND (use_p, def, iter, SSA_OP_USE)
{
tree t = USE_FROM_PTR (use_p);
/* If an SSA has already been seen, it may be a loop,
but we can continue and ignore this use. Otherwise,
add the SSA_NAME to the queue and visit it later. */
if (bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t)))
worklist.safe_push (t);
}
}
return false;
return ssa_name_maybe_undef_p (name);
}
/* Checks whether we can unswitch LOOP on condition at end of BB -- one of its