Case 7 of unsigned scalar saturating addition defines
SAT_ADD = X <= (X + Y) ? (X + Y) : -1. This is the same as
SAT_ADD = Y <= (X + Y) ? (X + Y) : -1 due to usadd_left_part_1
being commutative.
The pattern for case 7 currently does not accept the alternative
where Y is used in the condition. Therefore, this commit adds the
commutative property to this case which causes more valid cases of
unsigned saturating arithmetic to be recognised.
Before:
<bb 2>
_1 = BIT_FIELD_REF <b_3(D), 8, 0>;
sum_5 = _1 + a_4(D);
if (a_4(D) <= sum_5)
goto <bb 4>; [INV]
else
goto <bb 3>; [INV]
<bb 3> :
<bb 4> :
_2 = PHI <255(3), sum_5(2)>
return _2;
After:
<bb 2> [local count: 1073741824]:
_1 = BIT_FIELD_REF <b_3(D), 8, 0>;
_2 = .SAT_ADD (_1, a_4(D)); [tail call]
return _2;
This passes the aarch64-none-linux-gnu regression tests with no new
failures.
gcc/ChangeLog:
* match.pd: Modify existing case for SAT_ADD.
---
gcc/match.pd | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gcc/match.pd b/gcc/match.pd
index 4fc5efa6247..a77fca92181 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3166,7 +3166,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
/* Unsigned saturation add, case 7 (branch with le):
SAT_ADD = x <= (X + Y) ? (X + Y) : -1. */
(match (unsigned_integer_sat_add @0 @1)
- (cond^ (le @0 (usadd_left_part_1@2 @0 @1)) @2 integer_minus_onep))
+ (cond^ (le @0 (usadd_left_part_1:c@2 @0 @1)) @2 integer_minus_onep))
/* Unsigned saturation add, case 8 (branch with gt):
SAT_ADD = x > (X + Y) ? -1 : (X + Y). */
--
2.34.1
