Add __divmodti4 to match libgcc.

[craig.topper]

Summary

gcc has used this on x86-64 since at least version 7.

[craig.topper]

Ping

[MaskRay]

compiler-rt/test/builtins/Unit/divmodti4_test.c

26

Some existing builtins files do not strictly stick with the style but newer tests should place { at the line end.

61

The values can be organized as an array of structures.

[MaskRay]

compiler-rt/test/builtins/Unit/divmodti4_test.c

84

There is no test where the divisor has its high bits set. Will be good adding some coverage here.

[craig.topper]

compiler-rt/test/builtins/Unit/divmodti4_test.c

84

You mean just the high bit set?

[MaskRay]

compiler-rt/test/builtins/Unit/divmodti4_test.c

84

The high word. All the existing tests set the high word to 0.

[craig.topper]

compiler-rt/test/builtins/Unit/divmodti4_test.c

84

Don't the -1, -2, -3 divisors set the high bit of the high word?

[craig.topper]

Move test cases into an array.

[craig.topper]

Ping

compiler-rt/lib/builtins/CMakeLists.txt

set(GENERIC_SOURCES
   ctzdi2.c
   ctzsi2.c
   ctzti2.c
   divdc3.c
   divdf3.c
   divdi3.c
   divmoddi4.c
   divmodsi4.c
+  divmodti4.c
   divsc3.c
   divsf3.c
   divsi3.c
   divtc3.c
   divti3.c
   divtf3.c
   extendsfdf2.c
   extendhfsf2.c

compiler-rt/lib/builtins/README.txt

 ti_int __modti3    (ti_int a, ti_int b);               // a % b   signed
 su_int __umodsi3   (su_int a, su_int b);               // a % b   unsigned
 du_int __umoddi3   (du_int a, du_int b);               // a % b   unsigned
 tu_int __umodti3   (tu_int a, tu_int b);               // a % b   unsigned
 du_int __udivmoddi4(du_int a, du_int b, du_int* rem);  // a / b, *rem = a % b  unsigned
 tu_int __udivmodti4(tu_int a, tu_int b, tu_int* rem);  // a / b, *rem = a % b  unsigned
 su_int __udivmodsi4(su_int a, su_int b, su_int* rem);  // a / b, *rem = a % b  unsigned
 si_int __divmodsi4(si_int a, si_int b, si_int* rem);   // a / b, *rem = a % b  signed
+di_int __divmoddi4(di_int a, di_int b, di_int* rem);   // a / b, *rem = a % b  signed
+ti_int __divmodti4(ti_int a, ti_int b, ti_int* rem);   // a / b, *rem = a % b  signed
 
 
 
 //  Integral arithmetic with trapping overflow
 
 si_int __absvsi2(si_int a);           // abs(a)
 di_int __absvdi2(di_int a);           // abs(a)
 ti_int __absvti2(ti_int a);           // abs(a)

compiler-rt/lib/builtins/divmodti4.c

+//===-- divmodti4.c - Implement __divmodti4 -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __divmodti4 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "int_lib.h"
+
+#ifdef CRT_HAS_128BIT
+
+// Returns: a / b, *rem = a % b
+
+COMPILER_RT_ABI ti_int __divmodti4(ti_int a, ti_int b, ti_int *rem) {
+  const int bits_in_tword_m1 = (int)(sizeof(ti_int) * CHAR_BIT) - 1;
+  ti_int s_a = a >> bits_in_tword_m1;                   // s_a = a < 0 ? -1 : 0
+  ti_int s_b = b >> bits_in_tword_m1;                   // s_b = b < 0 ? -1 : 0
+  a = (a ^ s_a) - s_a;                                  // negate if s_a == -1
+  b = (b ^ s_b) - s_b;                                  // negate if s_b == -1
+  s_b ^= s_a;                                           // sign of quotient
+  tu_int r;
+  ti_int q = (__udivmodti4(a, b, &r) ^ s_b) - s_b;      // negate if s_b == -1
+  *rem = (r ^ s_a) - s_a;                               // negate if s_a == -1
+  return q;
+}
+
+#endif // CRT_HAS_128BIT

compiler-rt/test/builtins/Unit/divmodti4_test.c

+// RUN: %clang_builtins %s %librt -o %t && %run %t
+// REQUIRES: librt_has_divmodti4
+// REQUIRES: int128
+//===-- divmodti4_test.c - Test __divmodti4 -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file tests __divmodti4 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "int_lib.h"
+#include <stdio.h>
+
+#ifdef CRT_HAS_128BIT
+
+// Effects: if rem != 0, *rem = a % b
+// Returns: a / b
+
+COMPILER_RT_ABI ti_int __divmodti4(ti_int a, ti_int b, ti_int* rem);
+
+int test__divmodti4(ti_int a, ti_int b, ti_int expected_q, ti_int expected_r)
+{
+    ti_int r;
+    ti_int q = __divmodti4(a, b, &r);
+    if (q != expected_q || r != expected_r)
+    {
+        utwords at;
+        at.all = a;
+        utwords bt;
+        bt.all = b;
+        utwords expected_qt;
+        expected_qt.all = expected_q;
+        utwords expected_rt;
+        expected_rt.all = expected_r;
+        utwords qt;
+        qt.all = q;
+        utwords rt;
+        rt.all = r;
+        printf("error in __divmodti4: 0x%.16llX%.16llX / 0x%.16llX%.16llX = "
+               "0x%.16llX%.16llX, R = 0x%.16llX%.16llX, expected 0x%.16llX%.16llX, "
+               "0x%.16llX%.16llX\n",
+               at.s.high, at.s.low, bt.s.high, bt.s.low, qt.s.high, qt.s.low,
+               rt.s.high, rt.s.low, expected_qt.s.high, expected_qt.s.low,
+               expected_rt.s.high, expected_rt.s.low);
+    }
+    return !(q == expected_q && r == expected_r);
+}
+
+char assumption_1[sizeof(ti_int) == 2*sizeof(di_int)] = {0};
+
+#endif
+
+int main()
+{
+#ifdef CRT_HAS_128BIT
+    if (test__divmodti4(0, 1, 0, 0))
+        return 1;
+    if (test__divmodti4(0, -1, 0, 0))
+        return 1;
+
+    if (test__divmodti4(2, 1, 2, 0))
+        return 1;
+    if (test__divmodti4(2, -1, -2, 0))
+        return 1;
+    if (test__divmodti4(-2, 1, -2, 0))
+        return 1;
+    if (test__divmodti4(-2, -1, 2, 0))
+        return 1;
+
+    if (test__divmodti4(5, 3, 1, 2))
+        return 1;
+    if (test__divmodti4(5, -3, -1, 2))
+        return 1;
+    if (test__divmodti4(-5, 3, -1, -2))
+        return 1;
+    if (test__divmodti4(-5, -3, 1, -2))
+        return 1;
+
+    if (test__divmodti4(make_ti(0x8000000000000000LL, 0), 1, make_ti(0x8000000000000000LL, 0), 0x0LL))
+        return 1;
+    if (test__divmodti4(make_ti(0x8000000000000000LL, 0), -1, make_ti(0x8000000000000000LL, 0), 0x0LL))
+        return 1;
+    if (test__divmodti4(make_ti(0x8000000000000000LL, 0), -2, make_ti(0x4000000000000000LL, 0), 0x0LL))
+        return 1;
+    if (test__divmodti4(make_ti(0x8000000000000000LL, 0), 2, make_ti(0xC000000000000000LL, 0), 0x0LL))
+        return 1;
+    if (test__divmodti4(make_ti(0x8000000000000000LL, 0), -3, make_ti(0x2AAAAAAAAAAAAAAALL, 0xAAAAAAAAAAAAAAAALL), -2))
+        return 1;
+    if (test__divmodti4(make_ti(0x8000000000000000LL, 0), 3, make_ti(0xD555555555555555LL, 0x5555555555555556), -2))
+        return 1;
+#else
+    printf("skipped\n");
+#endif
+    return 0;
+}