Add truncxfhf2 with tests to compiler-rt (#120372)

Fixes #105181

compiler-rt/lib/builtins/CMakeLists.txt

@@ -310,6 +310,7 @@ set(x86_80_BIT_SOURCES
   mulxc3.c
   powixf2.c
   trunctfxf2.c
+  truncxfhf2.c
 )
 
 if (NOT MSVC)

compiler-rt/lib/builtins/truncxfhf2.c

@@ -0,0 +1,15 @@
+//===-- lib/truncsfhf2.c - long double -> half conversion ---------*- C -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#define SRC_SINGLE
+#define DST_HALF
+#include "fp_trunc_impl.inc"
+
+COMPILER_RT_ABI dst_t __truncxfhf2(xf_float a) {
+  return __truncXfYf2__((float)a);
+}

compiler-rt/test/builtins/Unit/truncxfhf2_test.c

@@ -0,0 +1,74 @@
+// RUN: %clang_builtins %s %librt -o %t && %run %t
+// REQUIRES: librt_has_truncxfhf2
+
+#include <stdio.h>
+
+#include "fp_test.h"
+
+#if HAS_80_BIT_LONG_DOUBLE
+
+TYPE_FP16 __truncxfhf2(xf_float f);
+
+int test_truncxfhf2(uint16_t inputHi, uint64_t inputLo, uint16_t e) {
+  xf_float a = F80FromRep80(inputHi, inputLo);
+  TYPE_FP16 x = __truncxfhf2(a);
+  int ret = compareResultH(x, e);
+  if (ret) {
+    printf("error in test__truncxfhf2(%Lf) = %#.4x, "
+           "expected %#.4x\n",
+           a, toRep16(x), e);
+  }
+  return ret;
+}
+
+int main() {
+  // Small positive value
+  if (test_truncxfhf2(UINT16_C(0x3ffb), UINT64_C(0xccc0000000000000),
+                      UINT16_C(0x2e66)))
+    return 1;
+
+  // Small negative value
+  if (test_truncxfhf2(UINT16_C(0xbffb), UINT64_C(0xccc0000000000000),
+                      UINT16_C(0xae66)))
+    return 1;
+
+  // Zero
+  if (test_truncxfhf2(UINT16_C(0x0), UINT64_C(0x0), UINT16_C(0)))
+    return 1;
+
+  // Smallest positive non-zero value
+  if (test_truncxfhf2(UINT16_C(0x3fef), UINT64_C(0x8000000000000000),
+                      UINT16_C(0x0100)))
+    return 1;
+
+  // Smallest negative non-zero value
+  if (test_truncxfhf2(UINT16_C(0xbfef), UINT64_C(0x8000000000000000),
+                      UINT16_C(0x8100)))
+    return 1;
+
+  // Positive infinity
+  if (test_truncxfhf2(UINT16_C(0x7fff), UINT64_C(0x8000000000000000),
+                      UINT16_C(0x7c00U)))
+    return 1;
+
+  // Negative infinity
+  if (test_truncxfhf2(UINT16_C(0xffff), UINT64_C(0x8000000000000000),
+                      UINT16_C(0xfc00U)))
+    return 1;
+
+  // NaN
+  if (test_truncxfhf2(UINT16_C(0x7fff), UINT64_C(0xc000000000000000),
+                      UINT16_C(0x7e00U)))
+    return 1;
+
+  return 0;
+}
+
+#else
+
+int main() {
+  printf("skipped\n");
+  return 0;
+}
+
+#endif