[libc][math][c23] Add sqrtf16 C23 math function

[overmighty]

Part of #95250.

[overmighty]

Re-opening this as #106102 was merged when it shouldn't have been (it was merged into the previous stacked PR's branch).

[llvmbot]

@llvm/pr-subscribers-libc

Author: OverMighty (overmighty)

Changes

Part of #95250.

---

Full diff: https://github.com/llvm/llvm-project/pull/112406.diff

14 Files Affected:

• (modified) libc/config/gpu/entrypoints.txt (+1)
• (modified) libc/config/linux/aarch64/entrypoints.txt (+1)
• (modified) libc/config/linux/x86_64/entrypoints.txt (+1)
• (modified) libc/docs/math/index.rst (+1-1)
• (modified) libc/spec/stdc.td (+1)
• (modified) libc/src/__support/FPUtil/generic/sqrt.h (+2-1)
• (modified) libc/src/math/CMakeLists.txt (+1)
• (modified) libc/src/math/generic/CMakeLists.txt (+12)
• (added) libc/src/math/generic/sqrtf16.cpp (+20)
• (added) libc/src/math/sqrtf16.h (+21)
• (modified) libc/test/src/math/CMakeLists.txt (+11)
• (modified) libc/test/src/math/smoke/CMakeLists.txt (+12)
• (added) libc/test/src/math/smoke/sqrtf16_test.cpp (+13)
• (added) libc/test/src/math/sqrtf16_test.cpp (+28)

diff --git a/libc/config/gpu/entrypoints.txt b/libc/config/gpu/entrypoints.txt
index 13bb88894297ca..38e9f2e685caed 100644
--- a/libc/config/gpu/entrypoints.txt
+++ b/libc/config/gpu/entrypoints.txt
@@ -590,6 +590,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.setpayloadf16
     libc.src.math.setpayloadsigf16
     libc.src.math.sinhf16
+    libc.src.math.sqrtf16
     libc.src.math.tanhf16
     libc.src.math.totalorderf16
     libc.src.math.totalordermagf16
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 885827d304efe3..71c6e874429fed 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -680,6 +680,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.setpayloadf16
     libc.src.math.setpayloadsigf16
     libc.src.math.sinpif16
+    libc.src.math.sqrtf16
     libc.src.math.totalorderf16
     libc.src.math.totalordermagf16
     libc.src.math.truncf16
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 6ed6ad8c2400f3..9bc63edf06f28c 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -684,6 +684,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.setpayloadsigf16
     libc.src.math.sinhf16
     libc.src.math.sinpif16
+    libc.src.math.sqrtf16
     libc.src.math.tanhf16
     libc.src.math.totalorderf16
     libc.src.math.totalordermagf16
diff --git a/libc/docs/math/index.rst b/libc/docs/math/index.rst
index 88751e2453f2c8..ce4df92393ce7f 100644
--- a/libc/docs/math/index.rst
+++ b/libc/docs/math/index.rst
@@ -344,7 +344,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | sinpi     | |check|          |                 |                        |  |check|             |                        | 7.12.4.13              | F.10.1.13                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| sqrt      | |check|          | |check|         | |check|                |                      | |check|                | 7.12.7.10              | F.10.4.10                  |
+| sqrt      | |check|          | |check|         | |check|                | |check|              | |check|                | 7.12.7.10              | F.10.4.10                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | tan       | |check|          | |check|         |                        |                      |                        | 7.12.4.7               | F.10.1.7                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
index 33bec2f71627e5..d1ebc6ffb5821e 100644
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -754,6 +754,7 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"sqrt", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
           FunctionSpec<"sqrtf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
           FunctionSpec<"sqrtl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
+          GuardedFunctionSpec<"sqrtf16", RetValSpec<Float16Type>, [ArgSpec<Float16Type>], "LIBC_TYPES_HAS_FLOAT16">,
           GuardedFunctionSpec<"sqrtf128", RetValSpec<Float128Type>, [ArgSpec<Float128Type>], "LIBC_TYPES_HAS_FLOAT128">,
 
           FunctionSpec<"trunc", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
diff --git a/libc/src/__support/FPUtil/generic/sqrt.h b/libc/src/__support/FPUtil/generic/sqrt.h
index 01af4bb7c90092..497ebd145c6b42 100644
--- a/libc/src/__support/FPUtil/generic/sqrt.h
+++ b/libc/src/__support/FPUtil/generic/sqrt.h
@@ -139,7 +139,8 @@ sqrt(InType x) {
       for (InStorageType current_bit = ONE >> 1; current_bit;
            current_bit >>= 1) {
         r <<= 1;
-        InStorageType tmp = (y << 1) + current_bit; // 2*y(n - 1) + 2^(-n-1)
+        // 2*y(n - 1) + 2^(-n-1)
+        InStorageType tmp = static_cast<InStorageType>((y << 1) + current_bit);
         if (r >= tmp) {
           r -= tmp;
           y += current_bit;
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
index 9239f029abf87a..cb4817348cbba5 100644
--- a/libc/src/math/CMakeLists.txt
+++ b/libc/src/math/CMakeLists.txt
@@ -492,6 +492,7 @@ add_math_entrypoint_object(sinhf16)
 add_math_entrypoint_object(sqrt)
 add_math_entrypoint_object(sqrtf)
 add_math_entrypoint_object(sqrtl)
+add_math_entrypoint_object(sqrtf16)
 add_math_entrypoint_object(sqrtf128)
 
 add_math_entrypoint_object(tan)
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 00cad6f85b4b98..35e7347b91362e 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -3249,6 +3249,18 @@ add_entrypoint_object(
     -O3
 )
 
+add_entrypoint_object(
+  sqrtf16
+  SRCS
+    sqrtf16.cpp
+  HDRS
+    ../sqrtf16.h
+  DEPENDS
+    libc.src.__support.FPUtil.sqrt
+  COMPILE_OPTIONS
+    -O3
+)
+
 add_entrypoint_object(
   sqrtf128
   SRCS
diff --git a/libc/src/math/generic/sqrtf16.cpp b/libc/src/math/generic/sqrtf16.cpp
new file mode 100644
index 00000000000000..0aa4a201b3e68c
--- /dev/null
+++ b/libc/src/math/generic/sqrtf16.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of sqrtf16 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/sqrtf16.h"
+#include "src/__support/FPUtil/sqrt.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(float16, sqrtf16, (float16 x)) {
+  return fputil::sqrt<float16>(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/sqrtf16.h b/libc/src/math/sqrtf16.h
new file mode 100644
index 00000000000000..bb09c4fdaf8d00
--- /dev/null
+++ b/libc/src/math/sqrtf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for sqrtf16 -----------------------*- 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_SQRTF16_H
+#define LLVM_LIBC_SRC_MATH_SQRTF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+float16 sqrtf16(float16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_SQRTF16_H
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index befa8cff0720cf..262c717dd27d55 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -1490,6 +1490,17 @@ add_fp_unittest(
     libc.src.math.sqrtl
 )
 
+add_fp_unittest(
+  sqrtf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    sqrtf16_test.cpp
+  DEPENDS
+    libc.src.math.sqrtf16
+)
+
 add_fp_unittest(
   generic_sqrtf_test
   NEED_MPFR
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index d41041c9bb0a4a..b2d1871541efc9 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -2889,6 +2889,18 @@ add_fp_unittest(
     libc.src.math.sqrtl
 )
 
+add_fp_unittest(
+  sqrtf16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    sqrtf16_test.cpp
+  HDRS
+    SqrtTest.h
+  DEPENDS
+    libc.src.math.sqrtf16
+)
+
 add_fp_unittest(
   sqrtf128_test
   SUITE
diff --git a/libc/test/src/math/smoke/sqrtf16_test.cpp b/libc/test/src/math/smoke/sqrtf16_test.cpp
new file mode 100644
index 00000000000000..d62049661eecbf
--- /dev/null
+++ b/libc/test/src/math/smoke/sqrtf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for sqrtf16 ---------------------------------------------===//
+//
+// 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 "SqrtTest.h"
+
+#include "src/math/sqrtf16.h"
+
+LIST_SQRT_TESTS(float16, LIBC_NAMESPACE::sqrtf16)
diff --git a/libc/test/src/math/sqrtf16_test.cpp b/libc/test/src/math/sqrtf16_test.cpp
new file mode 100644
index 00000000000000..f6e8996761245d
--- /dev/null
+++ b/libc/test/src/math/sqrtf16_test.cpp
@@ -0,0 +1,28 @@
+//===-- Exhaustive test for sqrtf16 ---------------------------------------===//
+//
+// 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/sqrtf16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcSqrtf16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+// Range: [0, Inf];
+static constexpr uint16_t POS_START = 0x0000U;
+static constexpr uint16_t POS_STOP = 0x7c00U;
+
+TEST_F(LlvmLibcSqrtf16Test, PositiveRange) {
+  for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
+    float16 x = FPBits(v).get_val();
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Sqrt, x,
+                                   LIBC_NAMESPACE::sqrtf16(x), 0.5);
+  }
+}