From: Pan Li <pan2...@intel.com> 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 <pan2...@intel.com> --- 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