[libc][math][c23] Add fmaf16 C23 math function. (#130757)

harrisonGPU · web-flow · commit 445837a36305 · 2025-03-23T10:48:56.000+08:00
Implementation of fmaf16 function for 16-bit inputs.
diff --git a/libc/config/gpu/amdgpu/entrypoints.txt b/libc/config/gpu/amdgpu/entrypoints.txt
@@ -548,6 +548,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.fabsf16
     libc.src.math.fdimf16
     libc.src.math.floorf16
+    libc.src.math.fmaf16
     libc.src.math.fmaxf16
     libc.src.math.fmaximum_mag_numf16
     libc.src.math.fmaximum_magf16
diff --git a/libc/config/gpu/nvptx/entrypoints.txt b/libc/config/gpu/nvptx/entrypoints.txt
@@ -550,6 +550,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.fabsf16
     libc.src.math.fdimf16
     libc.src.math.floorf16
+    libc.src.math.fmaf16
     libc.src.math.fmaxf16
     libc.src.math.fmaximum_mag_numf16
     libc.src.math.fmaximum_magf16
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -678,6 +678,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.ffma
     libc.src.math.ffmal
     libc.src.math.floorf16
+    libc.src.math.fmaf16
     libc.src.math.fmaxf16
     libc.src.math.fmaximum_mag_numf16
     libc.src.math.fmaximum_magf16
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -688,6 +688,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.fabsf16
     libc.src.math.fdimf16
     libc.src.math.floorf16
+    libc.src.math.fmaf16
     libc.src.math.fmaxf16
     libc.src.math.fmaximum_mag_numf16
     libc.src.math.fmaximum_magf16
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
@@ -299,7 +299,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | expm1     | |check|          | |check|         |                        | |check|              |                        | 7.12.6.6               | F.10.3.6                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| fma       | |check|          | |check|         |                        |                      |                        | 7.12.13.1              | F.10.10.1                  |
+| fma       | |check|          | |check|         |                        | |check|              |                        | 7.12.13.1              | F.10.10.1                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | f16sqrt   | |check|\*        | |check|\*       | |check|\*              | N/A                  | |check|                | 7.12.14.6              | F.10.11                    |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/include/math.yaml b/libc/include/math.yaml
@@ -749,6 +749,15 @@ functions:
       - type: float
       - type: float
       - type: float
+  - name: fmaf16
+    standards:
+      - stdc
+    return_type: _Float16
+    arguments:
+      - type: _Float16
+      - type: _Float16
+      - type: _Float16
+    guard: LIBC_TYPES_HAS_FLOAT16
   - name: fmax
     standards:
       - stdc
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -210,6 +210,7 @@ add_math_entrypoint_object(floorf128)
 
 add_math_entrypoint_object(fma)
 add_math_entrypoint_object(fmaf)
+add_math_entrypoint_object(fmaf16)
 
 add_math_entrypoint_object(fmax)
 add_math_entrypoint_object(fmaxf)
diff --git a/libc/src/math/fmaf16.h b/libc/src/math/fmaf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for fmaf16 ------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_MATH_FMAF16_H
+#define LLVM_LIBC_SRC_MATH_FMAF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+float16 fmaf16(float16 x, float16 y, float16 z);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_FMAF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -4287,6 +4287,17 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.fma
 )
 
+add_entrypoint_object(
+  fmaf16
+  SRCS
+    fmaf16.cpp
+  HDRS
+    ../fmaf16.h
+  DEPENDS
+    libc.src.__support.FPUtil.fma
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   fma
   SRCS
diff --git a/libc/src/math/generic/fmaf16.cpp b/libc/src/math/generic/fmaf16.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of fmaf16 function ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/fmaf16.h"
+#include "src/__support/FPUtil/FMA.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(float16, fmaf16, (float16 x, float16 y, float16 z)) {
+  return fputil::fma<float16>(x, y, z);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
@@ -1776,6 +1776,21 @@ add_fp_unittest(
     FMA_OPT__ONLY
 )
 
+add_fp_unittest(
+  fmaf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    fmaf16_test.cpp
+  HDRS
+    FmaTest.h
+  DEPENDS
+    libc.src.math.fmaf16
+    libc.src.stdlib.rand
+    libc.src.stdlib.srand
+)
+
 add_fp_unittest(
   fma_test
   NEED_MPFR
diff --git a/libc/test/src/math/FmaTest.h b/libc/test/src/math/FmaTest.h
@@ -58,8 +58,9 @@ class FmaTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
 
   void test_subnormal_range(FmaFunc func) {
     constexpr InStorageType COUNT = 100'001;
-    constexpr InStorageType STEP =
+    constexpr InStorageType RAW_STEP =
         (IN_MAX_SUBNORMAL_U - IN_MIN_SUBNORMAL_U) / COUNT;
+    constexpr InStorageType STEP = (RAW_STEP == 0 ? 1 : RAW_STEP);
     LIBC_NAMESPACE::srand(1);
     for (InStorageType v = IN_MIN_SUBNORMAL_U, w = IN_MAX_SUBNORMAL_U;
          v <= IN_MAX_SUBNORMAL_U && w >= IN_MIN_SUBNORMAL_U;
@@ -75,7 +76,9 @@ class FmaTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
 
   void test_normal_range(FmaFunc func) {
     constexpr InStorageType COUNT = 100'001;
-    constexpr InStorageType STEP = (IN_MAX_NORMAL_U - IN_MIN_NORMAL_U) / COUNT;
+    constexpr InStorageType RAW_STEP =
+        (IN_MAX_NORMAL_U - IN_MIN_NORMAL_U) / COUNT;
+    constexpr InStorageType STEP = (RAW_STEP == 0 ? 1 : RAW_STEP);
     LIBC_NAMESPACE::srand(1);
     for (InStorageType v = IN_MIN_NORMAL_U, w = IN_MAX_NORMAL_U;
          v <= IN_MAX_NORMAL_U && w >= IN_MIN_NORMAL_U; v += STEP, w -= STEP) {
diff --git a/libc/test/src/math/fmaf16_test.cpp b/libc/test/src/math/fmaf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for fmaf16 ----------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "FmaTest.h"
+
+#include "src/math/fmaf16.h"
+
+LIST_FMA_TESTS(float16, LIBC_NAMESPACE::fmaf16)
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
@@ -3562,6 +3562,19 @@ add_fp_unittest(
     libc.src.__support.macros.properties.types
 )
 
+add_fp_unittest(
+  fmaf16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    fmaf16_test.cpp
+  HDRS
+    FmaTest.h
+  DEPENDS
+    libc.src.math.fmaf16
+    libc.src.__support.FPUtil.cast
+)
+
 add_fp_unittest(
   fma_test
   SUITE
diff --git a/libc/test/src/math/smoke/FmaTest.h b/libc/test/src/math/smoke/FmaTest.h
@@ -9,9 +9,7 @@
 #ifndef LLVM_LIBC_TEST_SRC_MATH_FMATEST_H
 #define LLVM_LIBC_TEST_SRC_MATH_FMATEST_H
 
-#include "src/__support/CPP/type_traits.h"
 #include "src/__support/FPUtil/cast.h"
-#include "src/__support/macros/properties/types.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -90,14 +88,8 @@ class FmaTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
     // Test overflow.
     OutType z = out.max_normal;
     InType in_z = LIBC_NAMESPACE::fputil::cast<InType>(out.max_normal);
-#if defined(LIBC_TYPES_HAS_FLOAT16) && !defined(__LIBC_USE_FLOAT16_CONVERSION)
-    // Rounding modes other than the default might not be usable with float16.
-    if constexpr (LIBC_NAMESPACE::cpp::is_same_v<OutType, float16>)
-      EXPECT_FP_EQ(OutType(0.75) * z, func(InType(1.75), in_z, -in_z));
-    else
-#endif
-      EXPECT_FP_EQ_ALL_ROUNDING(OutType(0.75) * z,
-                                func(InType(1.75), in_z, -in_z));
+    EXPECT_FP_EQ_ALL_ROUNDING(OutType(0.75) * z,
+                              func(InType(1.75), in_z, -in_z));
 
     // Exact cancellation.
     EXPECT_FP_EQ_ROUNDING_NEAREST(
diff --git a/libc/test/src/math/smoke/fmaf16_test.cpp b/libc/test/src/math/smoke/fmaf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for fmaf16 ----------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "FmaTest.h"
+
+#include "src/math/fmaf16.h"
+
+LIST_FMA_TESTS(float16, LIBC_NAMESPACE::fmaf16)
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -454,6 +454,8 @@ explain_ternary_operation_one_output_error(Operation,
                                            long double, double, RoundingMode);
 
 #ifdef LIBC_TYPES_HAS_FLOAT16
+template void explain_ternary_operation_one_output_error(
+    Operation, const TernaryInput<float16> &, float16, double, RoundingMode);
 template void explain_ternary_operation_one_output_error(
     Operation, const TernaryInput<float> &, float16, double, RoundingMode);
 template void explain_ternary_operation_one_output_error(
@@ -672,6 +674,9 @@ compare_ternary_operation_one_output(Operation,
                                      long double, double, RoundingMode);
 
 #ifdef LIBC_TYPES_HAS_FLOAT16
+template bool
+compare_ternary_operation_one_output(Operation, const TernaryInput<float16> &,
+                                     float16, double, RoundingMode);
 template bool compare_ternary_operation_one_output(Operation,
                                                    const TernaryInput<float> &,
                                                    float16, double,
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2845,6 +2845,13 @@ libc_math_function(name = "floorf16")
 
 # TODO: Add fma, fmaf, fmal, fmaf128 functions.
 
+libc_math_function(
+    name = "fmaf16",
+    additional_deps = [
+        ":__support_fputil_fma",
+    ],
+)
+
 libc_math_function(name = "fmax")
 
 libc_math_function(name = "fmaxf")
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
@@ -476,6 +476,11 @@ math_test(
 
 # TODO: Add fma, fmaf, fmal, fmaf128 tests.
 
+math_test(
+    name = "fmaf16",
+    hdrs = ["FmaTest.h"],
+)
+
 math_test(
     name = "fmax",
     hdrs = ["FMaxTest.h"],
