re PR target/93141 (Missed optimization : Use of adc when checking overflow)

	PR target/93141
	* config/i386/i386.md (SWIDWI): New mode iterator.
	(DWI, dwi): Add TImode variants.
	(addv<mode>4): Use SWIDWI iterator instead of SWI.  Use
	<general_hilo_operand> instead of <general_operand>.  Use
	CONST_SCALAR_INT_P instead of CONST_INT_P.
	(*addv<mode>4_1): Rename to ...
	(addv<mode>4_1): ... this.
	(QWI): New mode attribute.
	(*addv<dwi>4_doubleword, *addv<dwi>4_doubleword_1): New
	define_insn_and_split patterns.
	(*addv<mode>4_overflow_1, *addv<mode>4_overflow_2): New define_insn
	patterns.
	(uaddv<mode>4): Use SWIDWI iterator instead of SWI.  Use
	<general_hilo_operand> instead of <general_operand>.
	(*addcarry<mode>_1): New define_insn.
	(*add<dwi>3_doubleword_cc_overflow_1): New define_insn_and_split.

	* gcc.target/i386/pr93141-1.c: New test.
	* gcc.dg/pr67089-6.c: Expect 16 ADD_OVERFLOW calls even on ia32.

From-SVN: r279887

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 181584a..e0a623e 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,23 @@
+2020-01-05  Jakub Jelinek  <jakub@redhat.com>
+
+       PR target/93141
+       * config/i386/i386.md (SWIDWI): New mode iterator.
+       (DWI, dwi): Add TImode variants.
+       (addv<mode>4): Use SWIDWI iterator instead of SWI.  Use
+       <general_hilo_operand> instead of <general_operand>.  Use
+       CONST_SCALAR_INT_P instead of CONST_INT_P.
+       (*addv<mode>4_1): Rename to ...
+       (addv<mode>4_1): ... this.
+       (QWI): New mode attribute.
+       (*addv<dwi>4_doubleword, *addv<dwi>4_doubleword_1): New
+       define_insn_and_split patterns.
+       (*addv<mode>4_overflow_1, *addv<mode>4_overflow_2): New define_insn
+       patterns.
+       (uaddv<mode>4): Use SWIDWI iterator instead of SWI.  Use
+       <general_hilo_operand> instead of <general_operand>.
+       (*addcarry<mode>_1): New define_insn.
+       (*add<dwi>3_doubleword_cc_overflow_1): New define_insn_and_split.
+
 2020-01-03  Konstantin Kharlamov  <Hi-Angel@yandex.ru>
 
        * gdbinit.in (pr, prl, pt, pct, pgg, pgq, pgs, pge, pmz, pdd, pbs, pbm):

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 01c7d65..50fb99a 100644 (file)
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -1036,6 +1036,9 @@
 (define_mode_iterator DWI [(DI "!TARGET_64BIT")
                           (TI "TARGET_64BIT")])
 
+;; SWI and DWI together.
+(define_mode_iterator SWIDWI [QI HI SI DI (TI "TARGET_64BIT")])
+
 ;; GET_MODE_SIZE for selected modes.  As GET_MODE_SIZE is not
 ;; compile time constant, it is faster to use <MODE_SIZE> than
 ;; GET_MODE_SIZE (<MODE>mode).  For XFmode which depends on
@@ -1051,8 +1054,8 @@
                             (V4SF "16") (V8SF "32") (V16SF "64")])
 
 ;; Double word integer modes as mode attribute.
-(define_mode_attr DWI [(QI "HI") (HI "SI") (SI "DI") (DI "TI")])
-(define_mode_attr dwi [(QI "hi") (HI "si") (SI "di") (DI "ti")])
+(define_mode_attr DWI [(QI "HI") (HI "SI") (SI "DI") (DI "TI") (TI "OI")])
+(define_mode_attr dwi [(QI "hi") (HI "si") (SI "di") (DI "ti") (TI "oi")])
 
 ;; LEA mode corresponding to an integer mode
 (define_mode_attr LEAMODE [(QI "SI") (HI "SI") (SI "SI") (DI "DI")])
@@ -6054,16 +6057,17 @@
 ;; Add with jump on overflow.
 (define_expand "addv<mode>4"
   [(parallel [(set (reg:CCO FLAGS_REG)
-                  (eq:CCO (plus:<DWI>
-                             (sign_extend:<DWI>
-                                (match_operand:SWI 1 "nonimmediate_operand"))
-                             (match_dup 4))
-                          (sign_extend:<DWI>
-                             (plus:SWI (match_dup 1)
-                                       (match_operand:SWI 2
-                                          "<general_operand>")))))
-             (set (match_operand:SWI 0 "register_operand")
-                  (plus:SWI (match_dup 1) (match_dup 2)))])
+                  (eq:CCO
+                    (plus:<DWI>
+                      (sign_extend:<DWI>
+                        (match_operand:SWIDWI 1 "nonimmediate_operand"))
+                      (match_dup 4))
+                        (sign_extend:<DWI>
+                          (plus:SWIDWI (match_dup 1)
+                            (match_operand:SWIDWI 2
+                              "<general_hilo_operand>")))))
+             (set (match_operand:SWIDWI 0 "register_operand")
+                  (plus:SWIDWI (match_dup 1) (match_dup 2)))])
    (set (pc) (if_then_else
               (eq (reg:CCO FLAGS_REG) (const_int 0))
               (label_ref (match_operand 3))
@@ -6071,7 +6075,7 @@
   ""
 {
   ix86_fixup_binary_operands_no_copy (PLUS, <MODE>mode, operands);
-  if (CONST_INT_P (operands[2]))
+  if (CONST_SCALAR_INT_P (operands[2]))
     operands[4] = operands[2];
   else
     operands[4] = gen_rtx_SIGN_EXTEND (<DWI>mode, operands[2]);
@@ -6093,7 +6097,7 @@
   [(set_attr "type" "alu")
    (set_attr "mode" "<MODE>")])
 
-(define_insn "*addv<mode>4_1"
+(define_insn "addv<mode>4_1"
   [(set (reg:CCO FLAGS_REG)
        (eq:CCO (plus:<DWI>
                   (sign_extend:<DWI>
@@ -6118,15 +6122,178 @@
                  (const_string "4")]
              (const_string "<MODE_SIZE>")))])
 
+;; Quad word integer modes as mode attribute.
+(define_mode_attr QWI [(SI "TI") (DI "OI")])
+
+(define_insn_and_split "*addv<dwi>4_doubleword"
+  [(set (reg:CCO FLAGS_REG)
+       (eq:CCO
+         (plus:<QWI>
+           (sign_extend:<QWI>
+             (match_operand:<DWI> 1 "nonimmediate_operand" "%0,0"))
+           (sign_extend:<QWI>
+             (match_operand:<DWI> 2 "x86_64_hilo_general_operand" "r<di>,o")))
+         (sign_extend:<QWI>
+           (plus:<DWI> (match_dup 1) (match_dup 2)))))
+   (set (match_operand:<DWI> 0 "nonimmediate_operand" "=ro,r")
+       (plus:<DWI> (match_dup 1) (match_dup 2)))]
+  "ix86_binary_operator_ok (PLUS, <DWI>mode, operands)"
+  "#"
+  "reload_completed"
+  [(parallel [(set (reg:CCC FLAGS_REG)
+                  (compare:CCC
+                    (plus:DWIH (match_dup 1) (match_dup 2))
+                    (match_dup 1)))
+             (set (match_dup 0)
+                  (plus:DWIH (match_dup 1) (match_dup 2)))])
+   (parallel [(set (reg:CCO FLAGS_REG)
+                  (eq:CCO
+                    (plus:<DWI>
+                      (plus:<DWI>
+                        (ltu:<DWI> (reg:CC FLAGS_REG) (const_int 0))
+                        (sign_extend:<DWI> (match_dup 4)))
+                      (sign_extend:<DWI> (match_dup 5)))
+                    (sign_extend:<DWI>
+                      (plus:DWIH
+                        (plus:DWIH
+                          (ltu:DWIH (reg:CC FLAGS_REG) (const_int 0))
+                          (match_dup 4))
+                        (match_dup 5)))))
+             (set (match_dup 3)
+                  (plus:DWIH
+                    (plus:DWIH
+                      (ltu:DWIH (reg:CC FLAGS_REG) (const_int 0))
+                      (match_dup 4))
+                    (match_dup 5)))])]
+{
+  split_double_mode (<DWI>mode, &operands[0], 3, &operands[0], &operands[3]);
+})
+
+(define_insn_and_split "*addv<dwi>4_doubleword_1"
+  [(set (reg:CCO FLAGS_REG)
+       (eq:CCO
+         (plus:<QWI>
+           (sign_extend:<QWI>
+             (match_operand:<DWI> 1 "nonimmediate_operand" "%0"))
+           (match_operand:<QWI> 3 "const_scalar_int_operand" ""))
+         (sign_extend:<QWI>
+           (plus:<DWI>
+             (match_dup 1)
+             (match_operand:<DWI> 2 "x86_64_hilo_general_operand" "<di>")))))
+   (set (match_operand:<DWI> 0 "nonimmediate_operand" "=ro")
+       (plus:<DWI> (match_dup 1) (match_dup 2)))]
+  "ix86_binary_operator_ok (PLUS, <DWI>mode, operands)
+   && CONST_SCALAR_INT_P (operands[2])
+   && rtx_equal_p (operands[2], operands[3])"
+  "#"
+  "reload_completed"
+  [(parallel [(set (reg:CCC FLAGS_REG)
+                  (compare:CCC
+                    (plus:DWIH (match_dup 1) (match_dup 2))
+                    (match_dup 1)))
+             (set (match_dup 0)
+                  (plus:DWIH (match_dup 1) (match_dup 2)))])
+   (parallel [(set (reg:CCO FLAGS_REG)
+                  (eq:CCO
+                    (plus:<DWI>
+                      (plus:<DWI>
+                        (ltu:<DWI> (reg:CC FLAGS_REG) (const_int 0))
+                        (sign_extend:<DWI> (match_dup 4)))
+                      (match_dup 5))
+                    (sign_extend:<DWI>
+                      (plus:DWIH
+                        (plus:DWIH
+                          (ltu:DWIH (reg:CC FLAGS_REG) (const_int 0))
+                          (match_dup 4))
+                        (match_dup 5)))))
+             (set (match_dup 3)
+                  (plus:DWIH
+                    (plus:DWIH
+                      (ltu:DWIH (reg:CC FLAGS_REG) (const_int 0))
+                      (match_dup 4))
+                    (match_dup 5)))])]
+{
+  split_double_mode (<DWI>mode, &operands[0], 3, &operands[0], &operands[3]);
+  if (operands[2] == const0_rtx)
+    {
+      emit_insn (gen_addv<mode>4_1 (operands[3], operands[4], operands[5],
+                                   operands[5]));
+      DONE;
+    }
+})
+
+(define_insn "*addv<mode>4_overflow_1"
+  [(set (reg:CCO FLAGS_REG)
+       (eq:CCO
+         (plus:<DWI>
+           (plus:<DWI>
+             (match_operator:<DWI> 4 "ix86_carry_flag_operator"
+               [(match_operand 3 "flags_reg_operand") (const_int 0)])
+             (sign_extend:<DWI>
+               (match_operand:SWI 1 "nonimmediate_operand" "%0,0")))
+           (sign_extend:<DWI>
+             (match_operand:SWI 2 "<general_sext_operand>" "rWe,m")))
+         (sign_extend:<DWI>
+           (plus:SWI
+             (plus:SWI
+               (match_operator:SWI 5 "ix86_carry_flag_operator"
+                 [(match_dup 3) (const_int 0)])
+               (match_dup 1))
+             (match_dup 2)))))
+   (set (match_operand:SWI 0 "nonimmediate_operand" "=rm,r")
+       (plus:SWI
+         (plus:SWI
+           (match_op_dup 5 [(match_dup 3) (const_int 0)])
+           (match_dup 1))
+         (match_dup 2)))]
+  "ix86_binary_operator_ok (PLUS, <MODE>mode, operands)"
+  "adc{<imodesuffix>}\t{%2, %0|%0, %2}"
+  [(set_attr "type" "alu")
+   (set_attr "mode" "<MODE>")])
+
+(define_insn "*addv<mode>4_overflow_2"
+  [(set (reg:CCO FLAGS_REG)
+       (eq:CCO
+         (plus:<DWI>
+           (plus:<DWI>
+             (match_operator:<DWI> 4 "ix86_carry_flag_operator"
+               [(match_operand 3 "flags_reg_operand") (const_int 0)])
+             (sign_extend:<DWI>
+               (match_operand:SWI 1 "nonimmediate_operand" "%0")))
+           (match_operand:<DWI> 6 "const_int_operand" ""))
+         (sign_extend:<DWI>
+           (plus:SWI
+             (plus:SWI
+               (match_operator:SWI 5 "ix86_carry_flag_operator"
+                 [(match_dup 3) (const_int 0)])
+               (match_dup 1))
+             (match_operand:SWI 2 "x86_64_immediate_operand" "e")))))
+   (set (match_operand:SWI 0 "nonimmediate_operand" "=rm")
+       (plus:SWI
+         (plus:SWI
+           (match_op_dup 5 [(match_dup 3) (const_int 0)])
+           (match_dup 1))
+         (match_dup 2)))]
+  "ix86_binary_operator_ok (PLUS, <MODE>mode, operands)
+   && CONST_INT_P (operands[2])
+   && INTVAL (operands[2]) == INTVAL (operands[6])"
+  "adc{<imodesuffix>}\t{%2, %0|%0, %2}"
+  [(set_attr "type" "alu")
+   (set_attr "mode" "<MODE>")
+   (set (attr "length_immediate")
+     (if_then_else (match_test "IN_RANGE (INTVAL (operands[2]), -128, 127)")
+       (const_string "1")
+       (const_string "4")))])
+
 (define_expand "uaddv<mode>4"
   [(parallel [(set (reg:CCC FLAGS_REG)
                   (compare:CCC
-                    (plus:SWI
-                      (match_operand:SWI 1 "nonimmediate_operand")
-                      (match_operand:SWI 2 "<general_operand>"))
+                    (plus:SWIDWI
+                      (match_operand:SWIDWI 1 "nonimmediate_operand")
+                      (match_operand:SWIDWI 2 "<general_hilo_operand>"))
                     (match_dup 1)))
-             (set (match_operand:SWI 0 "register_operand")
-                  (plus:SWI (match_dup 1) (match_dup 2)))])
+             (set (match_operand:SWIDWI 0 "register_operand")
+                  (plus:SWIDWI (match_dup 1) (match_dup 2)))])
    (set (pc) (if_then_else
               (ltu (reg:CCC FLAGS_REG) (const_int 0))
               (label_ref (match_operand 3))
@@ -6649,6 +6816,48 @@
           (plus:SWI48 (match_dup 1) (match_dup 2)))])]
   "ix86_binary_operator_ok (PLUS, <MODE>mode, operands)")
 
+(define_insn "*addcarry<mode>_1"
+  [(set (reg:CCC FLAGS_REG)
+       (compare:CCC
+         (zero_extend:<DWI>
+           (plus:SWI48
+             (plus:SWI48
+               (match_operator:SWI48 5 "ix86_carry_flag_operator"
+                 [(match_operand 3 "flags_reg_operand") (const_int 0)])
+               (match_operand:SWI48 1 "nonimmediate_operand" "%0"))
+             (match_operand:SWI48 2 "x86_64_immediate_operand" "e")))
+         (plus:<DWI>
+           (match_operand:<DWI> 6 "const_scalar_int_operand" "")
+           (match_operator:<DWI> 4 "ix86_carry_flag_operator"
+             [(match_dup 3) (const_int 0)]))))
+   (set (match_operand:SWI48 0 "register_operand" "=r")
+       (plus:SWI48 (plus:SWI48 (match_op_dup 5
+                                [(match_dup 3) (const_int 0)])
+                               (match_dup 1))
+                   (match_dup 2)))]
+  "ix86_binary_operator_ok (PLUS, <MODE>mode, operands)
+   && CONST_INT_P (operands[2])
+   /* Check that operands[6] is operands[2] zero extended from
+      <MODE>mode to <DWI>mode.  */
+   && ((<MODE>mode == SImode || INTVAL (operands[2]) >= 0)
+       ? (CONST_INT_P (operands[6])
+         && UINTVAL (operands[6]) == (UINTVAL (operands[2])
+                                      & GET_MODE_MASK (<MODE>mode)))
+       : (CONST_WIDE_INT_P (operands[6])
+         && CONST_WIDE_INT_NUNITS (operands[6]) == 2
+         && ((unsigned HOST_WIDE_INT) CONST_WIDE_INT_ELT (operands[6], 0)
+             == UINTVAL (operands[2]))
+         && CONST_WIDE_INT_ELT (operands[6], 1) == 0))"
+  "adc{<imodesuffix>}\t{%2, %0|%0, %2}"
+  [(set_attr "type" "alu")
+   (set_attr "use_carry" "1")
+   (set_attr "pent_pair" "pu")
+   (set_attr "mode" "<MODE>")
+   (set (attr "length_immediate")
+     (if_then_else (match_test "IN_RANGE (INTVAL (operands[2]), -128, 127)")
+       (const_string "1")
+       (const_string "4")))])
+
 (define_insn "@sub<mode>3_carry"
   [(set (match_operand:SWI 0 "nonimmediate_operand" "=<r>m,<r>")
        (minus:SWI
@@ -6885,6 +7094,54 @@
   [(set_attr "type" "alu")
    (set_attr "mode" "SI")])
 
+(define_insn_and_split "*add<dwi>3_doubleword_cc_overflow_1"
+  [(set (reg:CCC FLAGS_REG)
+       (compare:CCC
+         (plus:<DWI>
+           (match_operand:<DWI> 1 "nonimmediate_operand" "%0,0")
+           (match_operand:<DWI> 2 "x86_64_hilo_general_operand" "r<di>,o"))
+         (match_dup 1)))
+   (set (match_operand:<DWI> 0 "nonimmediate_operand" "=ro,r")
+       (plus:<DWI> (match_dup 1) (match_dup 2)))]
+  "ix86_binary_operator_ok (PLUS, <DWI>mode, operands)"
+  "#"
+  "reload_completed"
+  [(parallel [(set (reg:CCC FLAGS_REG)
+                  (compare:CCC
+                    (plus:DWIH (match_dup 1) (match_dup 2))
+                    (match_dup 1)))
+             (set (match_dup 0)
+                  (plus:DWIH (match_dup 1) (match_dup 2)))])
+   (parallel [(set (reg:CCC FLAGS_REG)
+                  (compare:CCC
+                    (zero_extend:<DWI>
+                      (plus:DWIH
+                        (plus:DWIH
+                          (ltu:DWIH (reg:CC FLAGS_REG) (const_int 0))
+                          (match_dup 4))
+                        (match_dup 5)))
+                    (plus:<DWI>
+                      (match_dup 6)
+                      (ltu:<DWI> (reg:CC FLAGS_REG) (const_int 0)))))
+             (set (match_dup 3)
+                  (plus:DWIH
+                    (plus:DWIH (ltu:DWIH (reg:CC FLAGS_REG) (const_int 0))
+                               (match_dup 4))
+                    (match_dup 5)))])]
+{
+  split_double_mode (<DWI>mode, &operands[0], 3, &operands[0], &operands[3]);
+  if (operands[2] == const0_rtx)
+    {
+      emit_insn (gen_addcarry<mode>_0 (operands[3], operands[4], operands[5]));
+      DONE;
+    }
+  if (CONST_INT_P (operands[5]))
+    operands[6] = simplify_unary_operation (ZERO_EXTEND, <DWI>mode,
+                                           operands[5], <MODE>mode);
+  else
+    operands[6] = gen_rtx_ZERO_EXTEND (<DWI>mode, operands[5]);
+})
+
 ;; x == 0 with zero flag test can be done also as x < 1U with carry flag
 ;; test, where the latter is preferrable if we have some carry consuming
 ;; instruction.

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c3f541b..76a25cc 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2020-01-05  Jakub Jelinek  <jakub@redhat.com>
 
+       PR target/93141
+       * gcc.target/i386/pr93141-1.c: New test.
+       * gcc.dg/pr67089-6.c: Expect 16 ADD_OVERFLOW calls even on ia32.
+
        PR c++/93138
        * g++.dg/warn/Wredundant-tags-2.C: New test.
 

diff --git a/gcc/testsuite/gcc.dg/pr67089-6.c b/gcc/testsuite/gcc.dg/pr67089-6.c
index 9b0708b..db2ffdf 100644 (file)
--- a/gcc/testsuite/gcc.dg/pr67089-6.c
+++ b/gcc/testsuite/gcc.dg/pr67089-6.c
@@ -56,7 +56,6 @@ T (24, unsigned long long, x + y, if (d || y > r) foo (0))
 T (25, unsigned short, 2U - x, if (r > 2U) foo (0))
 T (26, unsigned char, 2U - x, if (r <= 2U) foo (0))
 
-/* { dg-final { scan-tree-dump-times "ADD_OVERFLOW" 16 "widening_mul" { target { { i?86-*-* x86_64-*-* } && { ! ia32 } } } } } */
+/* { dg-final { scan-tree-dump-times "ADD_OVERFLOW" 16 "widening_mul" { target { i?86-*-* x86_64-*-* } } } } */
 /* { dg-final { scan-tree-dump-times "SUB_OVERFLOW" 11 "widening_mul" { target { { i?86-*-* x86_64-*-* } && { ! ia32 } } } } } */
-/* { dg-final { scan-tree-dump-times "ADD_OVERFLOW" 12 "widening_mul" { target { { i?86-*-* x86_64-*-* } && ia32 } } } } */
 /* { dg-final { scan-tree-dump-times "SUB_OVERFLOW" 9 "widening_mul" { target { { i?86-*-* x86_64-*-* } && ia32 } } } } */

diff --git a/gcc/testsuite/gcc.target/i386/pr93141-1.c b/gcc/testsuite/gcc.target/i386/pr93141-1.c
new file mode 100644 (file)
index 0000000..64e4a10
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr93141-1.c
@@ -0,0 +1,83 @@
+/* PR target/93141 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -masm=att" } */
+/* { dg-final { scan-assembler-not "cmp\[lq]\t" } } */
+/* { dg-final { scan-assembler-times "setc\t%" 3 } } */
+/* { dg-final { scan-assembler-times "seto\t%" 5 } } */
+/* { dg-final { scan-assembler-times "adc\[lq]\t" 5 } } */
+
+#ifdef __x86_64__
+typedef unsigned __int128 U;
+typedef signed __int128 S;
+#else
+typedef unsigned long long U;
+typedef signed long long S;
+#endif
+int o;
+
+U
+foo (U x, U y)
+{
+  U z;
+  o = __builtin_add_overflow (x, y, &z);
+  return z;
+}
+
+U
+bar (U x)
+{
+  U z;
+  o = __builtin_add_overflow (x, ((U) 0xdeadbee) << (sizeof (U) * __CHAR_BIT__ / 2), &z);
+  return z;
+}
+
+U
+baz (U x)
+{
+  U z;
+  o = __builtin_add_overflow (x, (((U) 0xdeadbee) << (sizeof (U) * __CHAR_BIT__ / 2))
+                                | (U) 0xbeedead, &z);
+  return z;
+}
+
+S
+qux (S x, S y)
+{
+  S z;
+  o = __builtin_add_overflow (x, y, &z);
+  return z;
+}
+
+S
+quux (S x)
+{
+  S z;
+  o = __builtin_add_overflow (x, ((S) 0xdeadbee) << (sizeof (S) * __CHAR_BIT__ / 2), &z);
+  return z;
+}
+
+S
+corge (S x)
+{
+  S z;
+  o = __builtin_add_overflow (x, (((S) 0xdeadbee) << (sizeof (S) * __CHAR_BIT__ / 2))
+                                | (S) 0xbeedead, &z);
+  return z;
+}
+
+S
+grault (S x)
+{
+  S z;
+  o = __builtin_add_overflow (x, -((S) 0xdeadbee) << (sizeof (S) * __CHAR_BIT__ / 2), &z);
+  return z;
+}
+
+S
+garply (S x)
+{
+  S z;
+  o = __builtin_add_overflow (x, (-(((S) 0xdeadbee) << (sizeof (S) * __CHAR_BIT__ / 2)))
+                                | (S) 0xbeedead, &z);
+  return z;
+}