From: Pan Li <[email protected]>
This patch would like to support the branch form for unsigned
SAT_ADD. For example as below:
uint64_t
sat_add (uint64_t x, uint64_t y)
{
return (uint64_t) (x + y) >= x ? (x + y) : -1;
}
Different to the branchless version, we leverage the simplify to
convert the branch version of SAT_ADD into branchless if and only
if the backend has supported the IFN_SAT_ADD. Thus, the backend has
the ability to choose branch or branchless implementation of .SAT_ADD.
For example, some target can take care of branches code more optimally.
When the target implement the IFN_SAT_ADD for unsigned and before this
patch:
uint64_t sat_add_u_1_uint64_t (uint64_t x, uint64_t y)
{
long unsigned int _1;
uint64_t _2;
__complex__ long unsigned int _6;
long unsigned int _7;
;; basic block 2, loop depth 0
;; pred: ENTRY
_6 = .ADD_OVERFLOW (x_3(D), y_4(D));
_1 = REALPART_EXPR <_6>;
_7 = IMAGPART_EXPR <_6>;
if (_7 == 0)
goto <bb 4>; [65.00%]
else
goto <bb 3>; [35.00%]
;; succ: 4
;; 3
;; basic block 3, loop depth 0
;; pred: 2
;; succ: 4
;; basic block 4, loop depth 0
;; pred: 3
;; 2
# _2 = PHI <18446744073709551615(3), _1(2)>
return _2;
;; succ: EXIT
}
After this patch:
uint64_t sat_add (uint64_t x, uint64_t y)
{
long unsigned int _9;
;; basic block 2, loop depth 0
;; pred: ENTRY
_9 = .SAT_ADD (x_3(D), y_4(D)); [tail call]
return _9;
;; succ: EXIT
}
The below test suites are passed for this patch:
* The x86 bootstrap test.
* The x86 fully regression test.
* The riscv fully regression test.
gcc/ChangeLog:
* match.pd: Add new simplify to convert branch SAT_ADD into
branchless, if and only if backend implement the IFN.
Signed-off-by: Pan Li <[email protected]>
---
gcc/match.pd | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/gcc/match.pd b/gcc/match.pd
index 0f9c34fa897..0547b57b3a3 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3094,6 +3094,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(match (unsigned_integer_sat_add @0 @1)
(bit_ior:c (usadd_left_part_2 @0 @1) (usadd_right_part_2 @0 @1)))
+#if GIMPLE
+
+/* Simplify the branch version of SAT_ADD into branchless if and only if
+ the backend has supported the IFN_SAT_ADD. Thus, the backend has the
+ ability to choose branch or branchless implementation of .SAT_ADD. */
+
+(simplify
+ (cond (ge (plus:c@2 @0 @1) @0) @2 integer_minus_onep)
+ (if (direct_internal_fn_supported_p (IFN_SAT_ADD, type, OPTIMIZE_FOR_BOTH))
+ (bit_ior @2 (negate (convert (lt @2 @0))))))
+
+(simplify
+ (cond (le @0 (plus:c@2 @0 @1)) @2 integer_minus_onep)
+ (if (direct_internal_fn_supported_p (IFN_SAT_ADD, type, OPTIMIZE_FOR_BOTH))
+ (bit_ior @2 (negate (convert (lt @2 @0))))))
+
+#endif
+
/* x > y && x != XXX_MIN --> x > y
x > y && x == XXX_MIN --> false . */
(for eqne (eq ne)
--
2.34.1
