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[compiler-rt] [builtins] Support conversion between fp16 and fp128
This patch adds both extendhftf2 and trunctfhf2 to support conversion between half-precision and quad-precision floating-point values. They are built iff the compiler supports _Float16. Some notes on ARM plaforms: while fp16 is supported on all architectures, _Float16 is supported only for 32-bit ARM, 64-bit ARM, and SPIR (as indicated by clang/docs/LanguageExtensions.rst). Also, fp16 is a storage format and 64-bit ARM supports floating-point convert precision to half as base armv8-a instruction. This patch does not change the ABI for 32-bit ARM, it will continue to pass _Float16 as uint16. This re-enabled revert done by https://reviews.llvm.org/rGb534beabeed3ba1777cd0ff9ce552d077e496726 Differential Revision: https://reviews.llvm.org/D92242
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‎compiler-rt/lib/builtins/CMakeLists.txt‎

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@@ -179,6 +179,7 @@ set(GENERIC_TF_SOURCES
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divtc3.c
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divtf3.c
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extenddftf2.c
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extendhftf2.c
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extendsftf2.c
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fixtfdi.c
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fixtfsi.c
@@ -197,6 +198,7 @@ set(GENERIC_TF_SOURCES
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powitf2.c
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subtf3.c
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trunctfdf2.c
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trunctfhf2.c
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trunctfsf2.c
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)
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‎compiler-rt/lib/builtins/extendhftf2.c‎

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//===-- lib/extendhftf2.c - half -> quad conversion ---------------*- C -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#define QUAD_PRECISION
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#include "fp_lib.h"
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#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT) && \
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defined(COMPILER_RT_HAS_FLOAT16)
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#define SRC_HALF
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#define DST_QUAD
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#include "fp_extend_impl.inc"
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COMPILER_RT_ABI long double __extendhftf2(_Float16 a) {
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return __extendXfYf2__(a);
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}
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#endif

‎compiler-rt/lib/builtins/trunctfhf2.c‎

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//===-- lib/trunctfhf2.c - quad -> half conversion ----------------*- C -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#define QUAD_PRECISION
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#include "fp_lib.h"
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#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT) && \
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defined(COMPILER_RT_HAS_FLOAT16)
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#define SRC_QUAD
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#define DST_HALF
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#include "fp_trunc_impl.inc"
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COMPILER_RT_ABI _Float16 __trunctfhf2(long double a) {
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return __truncXfYf2__(a);
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}
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#endif

‎compiler-rt/test/builtins/Unit/extendhftf2_test.c‎

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// RUN: %clang_builtins %s %librt -o %t && %run %t
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// REQUIRES: librt_has_extendhftf2
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#include "int_lib.h"
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#include <stdio.h>
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#if __LDBL_MANT_DIG__ == 113 && defined(COMPILER_RT_HAS_FLOAT16)
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#include "fp_test.h"
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COMPILER_RT_ABI long double __extendhftf2(TYPE_FP16 a);
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int test__extendhftf2(TYPE_FP16 a, uint64_t expectedHi, uint64_t expectedLo) {
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long double x = __extendhftf2(a);
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int ret = compareResultLD(x, expectedHi, expectedLo);
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if (ret) {
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printf("error in test__extendhftf2(%#.4x) = %.20Lf, "
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"expected %.20Lf\n",
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toRep16(a), x,
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fromRep128(expectedHi, expectedLo));
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}
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return ret;
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}
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char assumption_1[sizeof(TYPE_FP16) * CHAR_BIT == 16] = {0};
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#endif
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int main() {
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#if __LDBL_MANT_DIG__ == 113 && defined(COMPILER_RT_HAS_FLOAT16)
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// qNaN
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if (test__extendhftf2(makeQNaN16(),
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UINT64_C(0x7fff800000000000),
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UINT64_C(0x0)))
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return 1;
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// NaN
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if (test__extendhftf2(makeNaN16(UINT16_C(0x0100)),
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UINT64_C(0x7fff400000000000),
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UINT64_C(0x0)))
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return 1;
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// inf
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if (test__extendhftf2(makeInf16(),
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UINT64_C(0x7fff000000000000),
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UINT64_C(0x0)))
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return 1;
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if (test__extendhftf2(-makeInf16(),
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UINT64_C(0xffff000000000000),
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UINT64_C(0x0)))
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return 1;
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// zero
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if (test__extendhftf2(fromRep16(0x0U),
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UINT64_C(0x0), UINT64_C(0x0)))
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return 1;
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if (test__extendhftf2(fromRep16(0x8000U),
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UINT64_C(0x8000000000000000),
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UINT64_C(0x0)))
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return 1;
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// denormal
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if (test__extendhftf2(fromRep16(0x0010U),
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UINT64_C(0x3feb000000000000),
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UINT64_C(0x0000000000000000)))
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return 1;
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if (test__extendhftf2(fromRep16(0x0001U),
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UINT64_C(0x3fe7000000000000),
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UINT64_C(0x0000000000000000)))
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return 1;
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if (test__extendhftf2(fromRep16(0x8001U),
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UINT64_C(0xbfe7000000000000),
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UINT64_C(0x0000000000000000)))
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return 1;
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// pi
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if (test__extendhftf2(fromRep16(0x4248U),
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UINT64_C(0x4000920000000000),
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UINT64_C(0x0000000000000000)))
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return 1;
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if (test__extendhftf2(fromRep16(0xc248U),
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UINT64_C(0xc000920000000000),
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UINT64_C(0x0000000000000000)))
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return 1;
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if (test__extendhftf2(fromRep16(0x508cU),
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UINT64_C(0x4004230000000000),
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UINT64_C(0x0)))
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return 1;
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if (test__extendhftf2(fromRep16(0x1bb7U),
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UINT64_C(0x3ff6edc000000000),
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UINT64_C(0x0)))
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return 1;
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#else
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printf("skipped\n");
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#endif
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return 0;
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}

‎compiler-rt/test/builtins/Unit/trunctfhf2_test.c‎

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// RUN: %clang_builtins %s %librt -o %t && %run %t
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// REQUIRES: librt_has_trunctfhf2
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#include "int_lib.h"
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#include <stdio.h>
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#if __LDBL_MANT_DIG__ == 113 && defined(COMPILER_RT_HAS_FLOAT16)
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#include "fp_test.h"
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TYPE_FP16 __trunctfhf2(long double a);
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int test__trunctfhf2(long double a, uint16_t expected) {
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TYPE_FP16 x = __trunctfhf2(a);
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int ret = compareResultH(x, expected);
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if (ret) {
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printf("error in test__trunctfhf2(%.20Lf) = %#.4x, "
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"expected %#.4x\n",
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a, toRep16(x), expected);
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}
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return ret;
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}
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char assumption_1[sizeof(TYPE_FP16) * CHAR_BIT == 16] = {0};
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#endif
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int main() {
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#if __LDBL_MANT_DIG__ == 113 && defined(COMPILER_RT_HAS_FLOAT16)
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// qNaN
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if (test__trunctfhf2(makeQNaN128(),
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UINT16_C(0x7e00)))
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return 1;
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// NaN
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if (test__trunctfhf2(makeNaN128(UINT64_C(0x810000000000)),
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UINT16_C(0x7e00)))
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return 1;
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// inf
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if (test__trunctfhf2(makeInf128(),
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UINT16_C(0x7c00)))
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return 1;
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if (test__trunctfhf2(-makeInf128(),
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UINT16_C(0xfc00)))
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return 1;
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// zero
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if (test__trunctfhf2(0.0L, UINT16_C(0x0)))
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return 1;
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if (test__trunctfhf2(-0.0L, UINT16_C(0x8000)))
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return 1;
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if (test__trunctfhf2(3.1415926535L,
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UINT16_C(0x4248)))
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return 1;
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if (test__trunctfhf2(-3.1415926535L,
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UINT16_C(0xc248)))
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return 1;
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if (test__trunctfhf2(0x1.987124876876324p+100L,
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UINT16_C(0x7c00)))
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return 1;
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if (test__trunctfhf2(0x1.987124876876324p+12L,
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UINT16_C(0x6e62)))
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return 1;
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if (test__trunctfhf2(0x1.0p+0L,
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UINT16_C(0x3c00)))
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return 1;
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if (test__trunctfhf2(0x1.0p-14L,
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UINT16_C(0x0400)))
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return 1;
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// denormal
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if (test__trunctfhf2(0x1.0p-20L,
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UINT16_C(0x0010)))
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return 1;
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if (test__trunctfhf2(0x1.0p-24L,
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UINT16_C(0x0001)))
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return 1;
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if (test__trunctfhf2(-0x1.0p-24L,
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UINT16_C(0x8001)))
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return 1;
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if (test__trunctfhf2(0x1.5p-25L,
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UINT16_C(0x0001)))
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return 1;
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// and back to zero
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if (test__trunctfhf2(0x1.0p-25L,
85+
UINT16_C(0x0000)))
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return 1;
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if (test__trunctfhf2(-0x1.0p-25L,
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UINT16_C(0x8000)))
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return 1;
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// max (precise)
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if (test__trunctfhf2(65504.0L,
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UINT16_C(0x7bff)))
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return 1;
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// max (rounded)
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if (test__trunctfhf2(65519.0L,
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UINT16_C(0x7bff)))
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return 1;
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// max (to +inf)
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if (test__trunctfhf2(65520.0L,
100+
UINT16_C(0x7c00)))
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return 1;
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if (test__trunctfhf2(65536.0L,
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UINT16_C(0x7c00)))
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return 1;
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if (test__trunctfhf2(-65520.0L,
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UINT16_C(0xfc00)))
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return 1;
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if (test__trunctfhf2(0x1.23a2abb4a2ddee355f36789abcdep+5L,
110+
UINT16_C(0x508f)))
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return 1;
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if (test__trunctfhf2(0x1.e3d3c45bd3abfd98b76a54cc321fp-9L,
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UINT16_C(0x1b8f)))
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return 1;
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if (test__trunctfhf2(0x1.234eebb5faa678f4488693abcdefp+453L,
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UINT16_C(0x7c00)))
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return 1;
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if (test__trunctfhf2(0x1.edcba9bb8c76a5a43dd21f334634p-43L,
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UINT16_C(0x0)))
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return 1;
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#else
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printf("skipped\n");
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#endif
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return 0;
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}

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