Richard,
in looking at how simplify_abs_using_ranges was doing its thing as a guide to a
min/max vrp optimization, I noticed it was doing more work than necessary.
Firstly, it wasn't taking advantage of the range comparison functions only
returning TRUE or FALSE nodes when there's a definite answer, and NULL
otherwise. Thus if we get a node, we don't have to (a) check if it's either
true or false and (b) we only need to check for one of those values to determine
which specific answer was given.
Also, it was checking for 'NOT (A >= B)' by inverting the result of a '>='
check, rather than simply doing a '<' check. (we're dealing with integer ranges,
so that's all well defined)
Finally, there's a useless check for UNSIGNED_TYPE, which ends up doing nothing.
AFAICT 'ABS (unsigned)' gets folded out very early on.
booted and tested with the phi-min-max fix I just posted and the new VRP-min-max
optimization I'm about to.
ok?
nathan
2015-08-10 Nathan Sidwell <nat...@acm.org>
* tree-vrp.c (simplify_abs_using_ranges): Simplify.
Index: tree-vrp.c
===================================================================
--- tree-vrp.c (revision 226749)
+++ tree-vrp.c (working copy)
@@ -9152,37 +9215,25 @@ simplify_div_or_mod_using_ranges (gimple
static bool
simplify_abs_using_ranges (gimple stmt)
{
- tree val = NULL;
tree op = gimple_assign_rhs1 (stmt);
- tree type = TREE_TYPE (op);
value_range_t *vr = get_value_range (op);
- if (TYPE_UNSIGNED (type))
- {
- val = integer_zero_node;
- }
- else if (vr)
+ if (vr)
{
+ tree val = NULL;
bool sop = false;
val = compare_range_with_value (LE_EXPR, vr, integer_zero_node, &sop);
if (!val)
{
+ /* The range is neither <= 0 nor > 0. Now see if it is
+ either < 0 or >= 0. */
sop = false;
- val = compare_range_with_value (GE_EXPR, vr, integer_zero_node,
+ val = compare_range_with_value (LT_EXPR, vr, integer_zero_node,
&sop);
-
- if (val)
- {
- if (integer_zerop (val))
- val = integer_one_node;
- else if (integer_onep (val))
- val = integer_zero_node;
- }
}
- if (val
- && (integer_onep (val) || integer_zerop (val)))
+ if (val)
{
if (sop && issue_strict_overflow_warning (WARN_STRICT_OVERFLOW_MISC))
{
@@ -9198,10 +9249,10 @@ simplify_abs_using_ranges (gimple stmt)
}
gimple_assign_set_rhs1 (stmt, op);
- if (integer_onep (val))
- gimple_assign_set_rhs_code (stmt, NEGATE_EXPR);
- else
+ if (integer_zerop (val))
gimple_assign_set_rhs_code (stmt, SSA_NAME);
+ else
+ gimple_assign_set_rhs_code (stmt, NEGATE_EXPR);
update_stmt (stmt);
return true;
}
