[COMPILER-RT] Implement __multf3

[koviankevin]

Summary

Implement __multf3, which performs long double multiplication

[koviankevin]

add test

[koviankevin]

Use CRT_HAS_128BIT and modify the codes according to gribozavr's comments

[koviankevin]

introduce CRT_LDBL_128BIT

[koviankevin]

modify by gribozavr's comment and use COMPILER_RT_ABI

[joerg]

Similar to D2798, please refactor first as one commit. Please make sure the changed "underflow to zero" case is covered by a test case.

[koviankevin]

use UINT64_C and drop le64
muldf3.c and mulsf3.c are refactored in D3886

[joerg]

Closed by commit rL211313 (authored by @joerg).

compiler-rt/trunk/lib/builtins/CMakeLists.txt

set(GENERIC_SOURCES
   muldf3.c
   muldi3.c
   mulodi4.c
   mulosi4.c
   muloti4.c
   mulsc3.c
   mulsf3.c
   multi3.c
+  multf3.c
   mulvdi3.c
   mulvsi3.c
   mulvti3.c
   mulxc3.c
   negdf2.c
   negdi2.c
   negsf2.c
   negti2.c

compiler-rt/trunk/lib/builtins/multf3.c

+//===-- lib/multf3.c - Quad-precision multiplication --------------*- C -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements quad-precision soft-float multiplication
+// with the IEEE-754 default rounding (to nearest, ties to even).
+//
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
+#include "fp_mul_impl.inc"
+
+COMPILER_RT_ABI fp_t __multf3(fp_t a, fp_t b) {
+    return __mulXf3__(a, b);
+}
+
+#endif

compiler-rt/trunk/test/builtins/Unit/multf3_test.c

+//===--------------- multf3_test.c - Test __multf3 ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file tests __multf3 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdio.h>
+
+#if __LDBL_MANT_DIG__ == 113
+
+#include "fp_test.h"
+
+// Returns: a * b
+long double __multf3(long double a, long double b);
+
+int test__multf3(long double a, long double b,
+                 uint64_t expectedHi, uint64_t expectedLo)
+{
+    long double x = __multf3(a, b);
+    int ret = compareResultLD(x, expectedHi, expectedLo);
+
+    if (ret){
+        printf("error in test__multf3(%.20Lf, %.20Lf) = %.20Lf, "
+               "expected %.20Lf\n", a, b, x,
+               fromRep128(expectedHi, expectedLo));
+    }
+    return ret;
+}
+
+char assumption_1[sizeof(long double) * CHAR_BIT == 128] = {0};
+
+#endif
+
+int main()
+{
+#if __LDBL_MANT_DIG__ == 113
+    // qNaN * any = qNaN
+    if (test__multf3(makeQNaN128(),
+                     0x1.23456789abcdefp+5L,
+                     UINT64_C(0x7fff800000000000),
+                     UINT64_C(0x0)))
+        return 1;
+    // NaN * any = NaN
+    if (test__multf3(makeNaN128(UINT64_C(0x800030000000)),
+                     0x1.23456789abcdefp+5L,
+                     UINT64_C(0x7fff800000000000),
+                     UINT64_C(0x0)))
+        return 1;
+    // inf * any = inf
+    if (test__multf3(makeInf128(),
+                     0x1.23456789abcdefp+5L,
+                     UINT64_C(0x7fff000000000000),
+                     UINT64_C(0x0)))
+        return 1;
+    // any * any
+    if (test__multf3(0x1.2eab345678439abcdefea56782346p+5L,
+                     0x1.edcb34a235253948765432134674fp-1L,
+                     UINT64_C(0x400423e7f9e3c9fc),
+                     UINT64_C(0xd906c2c2a85777c4)))
+        return 1;
+    if (test__multf3(0x1.353e45674d89abacc3a2ebf3ff4ffp-50L,
+                     0x1.ed8764648369535adf4be3214567fp-9L,
+                     UINT64_C(0x3fc52a163c6223fc),
+                     UINT64_C(0xc94c4bf0430768b4)))
+        return 1;
+    if (test__multf3(0x1.234425696abcad34a35eeffefdcbap+456L,
+                     0x451.ed98d76e5d46e5f24323dff21ffp+600L,
+                     UINT64_C(0x44293a91de5e0e94),
+                     UINT64_C(0xe8ed17cc2cdf64ac)))
+        return 1;
+    if (test__multf3(0x1.4356473c82a9fabf2d22ace345defp-234L,
+                     0x1.eda98765476743ab21da23d45678fp-455L,
+                     UINT64_C(0x3d4f37c1a3137cae),
+                     UINT64_C(0xfc6807048bc2836a)))
+        return 1;
+    // underflow
+    if (test__multf3(0x1.23456734245345p-10000L,
+                     0x1.edcba524498724p-6383L,
+                     UINT64_C(0x0),
+                     UINT64_C(0x0)))
+        return 1;
+
+#else
+    printf("skipped\n");
+
+#endif
+    return 0;
+}