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Enhance SCEV to follow copies of SSA_NAMEs.

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(Fixes missed vectorization of gcc.dg/vect/pr65947-2.c.)

        * tree-scalar-evolution.c (follow_copies_to_constant): New.
        (analyze_initial_condition, analyze_scalar_evolution_1): Call previous.

From-SVN: r232509
This commit is contained in:
Alan Lawrence 2016-01-18 12:46:54 +00:00 committed by Alan Lawrence
parent 70c1e88677
commit 806f2c1b28
2 changed files with 38 additions and 17 deletions

5
gcc/ChangeLog

@ -1,3 +1,8 @@
2016-01-18 Alan Lawrence <alan.lawrence@arm.com>
* tree-scalar-evolution.c (follow_copies_to_constant): New.
(analyze_initial_condition, analyze_scalar_evolution_1): Call previous.
2016-01-18 Alan Lawrence <alan.lawrence@arm.com>
PR target/63679

50
gcc/tree-scalar-evolution.c

@ -1522,6 +1522,34 @@ analyze_evolution_in_loop (gphi *loop_phi_node,
return evolution_function;
}
/* Looks to see if VAR is a copy of a constant (via straightforward assignments
or degenerate phi's). If so, returns the constant; else, returns VAR. */
static tree
follow_copies_to_constant (tree var)
{
tree res = var;
while (TREE_CODE (res) == SSA_NAME)
{
gimple *def = SSA_NAME_DEF_STMT (res);
if (gphi *phi = dyn_cast <gphi *> (def))
{
if (tree rhs = degenerate_phi_result (phi))
res = rhs;
else
break;
}
else if (gimple_assign_single_p (def))
/* Will exit loop if not an SSA_NAME. */
res = gimple_assign_rhs1 (def);
else
break;
}
if (CONSTANT_CLASS_P (res))
return res;
return var;
}
/* Given a loop-phi-node, return the initial conditions of the
variable on entry of the loop. When the CCP has propagated
constants into the loop-phi-node, the initial condition is
@ -1574,21 +1602,9 @@ analyze_initial_condition (gphi *loop_phi_node)
if (init_cond == chrec_not_analyzed_yet)
init_cond = chrec_dont_know;
/* During early loop unrolling we do not have fully constant propagated IL.
Handle degenerate PHIs here to not miss important unrollings. */
if (TREE_CODE (init_cond) == SSA_NAME)
{
gimple *def = SSA_NAME_DEF_STMT (init_cond);
if (gphi *phi = dyn_cast <gphi *> (def))
{
tree res = degenerate_phi_result (phi);
if (res != NULL_TREE
/* Only allow invariants here, otherwise we may break
loop-closed SSA form. */
&& is_gimple_min_invariant (res))
init_cond = res;
}
}
/* We may not have fully constant propagated IL. Handle degenerate PHIs here
to not miss important early loop unrollings. */
init_cond = follow_copies_to_constant (init_cond);
if (dump_file && (dump_flags & TDF_SCEV))
{
@ -1968,8 +1984,8 @@ analyze_scalar_evolution_1 (struct loop *loop, tree var, tree res)
if (bb == NULL
|| !flow_bb_inside_loop_p (loop, bb))
{
/* Keep the symbolic form. */
res = var;
/* Keep symbolic form, but look through obvious copies for constants. */
res = follow_copies_to_constant (var);
goto set_and_end;
}