[libc][math][c++23] Add scalb{,l}nbf16 math functions (#155569)

krishna2803 · web-flow · commit a985be6fdfe3 · 2025-08-28T20:29:03.000+05:30
This PR adds the following basic math functions for BFloat16 type along
with the tests:
- scalbnbf16
- scalblnbf16

---------

Signed-off-by: Krishna Pandey &lt;kpandey81930@gmail.com&gt;
diff --git a/libc/config/baremetal/aarch64/entrypoints.txt b/libc/config/baremetal/aarch64/entrypoints.txt
@@ -814,6 +814,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
@@ -817,6 +817,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/baremetal/riscv/entrypoints.txt b/libc/config/baremetal/riscv/entrypoints.txt
@@ -817,6 +817,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/darwin/aarch64/entrypoints.txt b/libc/config/darwin/aarch64/entrypoints.txt
@@ -647,6 +647,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/darwin/x86_64/entrypoints.txt b/libc/config/darwin/x86_64/entrypoints.txt
@@ -290,6 +290,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/gpu/amdgpu/entrypoints.txt b/libc/config/gpu/amdgpu/entrypoints.txt
@@ -673,6 +673,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/gpu/nvptx/entrypoints.txt b/libc/config/gpu/nvptx/entrypoints.txt
@@ -675,6 +675,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -902,6 +902,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/arm/entrypoints.txt b/libc/config/linux/arm/entrypoints.txt
@@ -517,6 +517,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
@@ -920,6 +920,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -953,6 +953,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
@@ -363,6 +363,8 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.rintbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
+  libc.src.math.scalblnbf16
+  libc.src.math.scalbnbf16
   libc.src.math.setpayloadbf16
   libc.src.math.setpayloadsigbf16
   libc.src.math.truncbf16
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
@@ -233,9 +233,9 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | roundeven        | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.9.8               | F.10.6.8                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| scalbln          | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.6.19              | F.10.3.19                  |
+| scalbln          | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.6.19              | F.10.3.19                  |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| scalbn           | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.6.19              | F.10.3.19                  |
+| scalbn           | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.6.19              | F.10.3.19                  |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | setpayload       | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | F.10.13.2              | N/A                        |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -518,12 +518,14 @@ add_math_entrypoint_object(scalblnf)
 add_math_entrypoint_object(scalblnl)
 add_math_entrypoint_object(scalblnf16)
 add_math_entrypoint_object(scalblnf128)
+add_math_entrypoint_object(scalblnbf16)
 
 add_math_entrypoint_object(scalbn)
 add_math_entrypoint_object(scalbnf)
 add_math_entrypoint_object(scalbnl)
 add_math_entrypoint_object(scalbnf16)
 add_math_entrypoint_object(scalbnf128)
+add_math_entrypoint_object(scalbnbf16)
 
 add_math_entrypoint_object(setpayload)
 add_math_entrypoint_object(setpayloadf)
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -4646,6 +4646,21 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  scalblnbf16
+  SRCS
+    scalblnbf16.cpp
+  HDRS
+    ../scalblnbf16.h
+  DEPENDS
+    libc.hdr.float_macros
+    libc.src.__support.common
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.manipulation_functions
+)
+
 add_entrypoint_object(
   scalbn
   SRCS
@@ -4703,6 +4718,21 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  scalbnbf16
+  SRCS
+    scalbnbf16.cpp
+  HDRS
+    ../scalblnbf16.h
+  DEPENDS
+    libc.hdr.float_macros
+    libc.src.__support.common
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.manipulation_functions
+)
+
 add_entrypoint_object(
   fmaf
   SRCS
diff --git a/libc/src/math/generic/scalblnbf16.cpp b/libc/src/math/generic/scalblnbf16.cpp
@@ -0,0 +1,26 @@
+//===-- Implementation of scalblnbf16 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/scalblnbf16.h"
+#include "hdr/float_macros.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+#if FLT_RADIX != 2
+#error "FLT_RADIX != 2 is not supported."
+#endif
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, scalblnbf16, (bfloat16 x, long n)) {
+  return fputil::ldexp(x, n);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/generic/scalbnbf16.cpp b/libc/src/math/generic/scalbnbf16.cpp
@@ -0,0 +1,26 @@
+//===-- Implementation of scalbnbf16 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/scalbnbf16.h"
+#include "hdr/float_macros.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+#if FLT_RADIX != 2
+#error "FLT_RADIX != 2 is not supported."
+#endif
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, scalbnbf16, (bfloat16 x, int n)) {
+  return fputil::ldexp(x, n);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/scalblnbf16.h b/libc/src/math/scalblnbf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for scalblnbf16 -------------------*- 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_SCALBLNBF16_H
+#define LLVM_LIBC_SRC_MATH_SCALBLNBF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+bfloat16 scalblnbf16(bfloat16 x, long n);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_SCALBLNBF16_H
diff --git a/libc/src/math/scalbnbf16.h b/libc/src/math/scalbnbf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for scalbnbf16 --------------------*- 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_SCALBNBF16_H
+#define LLVM_LIBC_SRC_MATH_SCALBNBF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+bfloat16 scalbnbf16(bfloat16 x, int n);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_SCALBNBF16_H
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
@@ -4881,6 +4881,22 @@ add_fp_unittest(
     libc.src.__support.FPUtil.normal_float
 )
 
+add_fp_unittest(
+  scalblnbf16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    scalblnbf16_test.cpp
+  HDRS
+    ScalbnTest.h
+  DEPENDS
+    libc.src.math.scalblnbf16
+    libc.src.__support.CPP.limits
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.normal_float
+)
+
 add_fp_unittest(
   scalbn_test
   SUITE
@@ -4956,6 +4972,22 @@ add_fp_unittest(
     libc.src.__support.FPUtil.normal_float
 )
 
+add_fp_unittest(
+  scalbnbf16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    scalbnbf16_test.cpp
+  HDRS
+    ScalbnTest.h
+  DEPENDS
+    libc.src.math.scalbnbf16
+    libc.src.__support.CPP.limits
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.normal_float
+)
+
 add_fp_unittest(
   erff_test
   SUITE
diff --git a/libc/test/src/math/smoke/TotalOrderMagTest.h b/libc/test/src/math/smoke/TotalOrderMagTest.h
@@ -107,6 +107,11 @@ class TotalOrderMagTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
 
   void testNaNPayloads(TotalOrderMagFunc func) {
 
+    T qnan_0x15 = FPBits::quiet_nan(Sign::POS, 0x15).get_val();
+    T neg_qnan_0x15 = FPBits::quiet_nan(Sign::NEG, 0x15).get_val();
+    T snan_0x15 = FPBits::signaling_nan(Sign::POS, 0x15).get_val();
+    T neg_snan_0x15 = FPBits::signaling_nan(Sign::NEG, 0x15).get_val();
+
     EXPECT_TRUE(funcWrapper(func, aNaN, aNaN));
     EXPECT_TRUE(funcWrapper(func, sNaN, sNaN));
 
diff --git a/libc/test/src/math/smoke/TotalOrderTest.h b/libc/test/src/math/smoke/TotalOrderTest.h
@@ -105,6 +105,11 @@ class TotalOrderTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
 
   void testNaNPayloads(TotalOrderFunc func) {
 
+    T qnan_0x15 = FPBits::quiet_nan(Sign::POS, 0x15).get_val();
+    T neg_qnan_0x15 = FPBits::quiet_nan(Sign::NEG, 0x15).get_val();
+    T snan_0x15 = FPBits::signaling_nan(Sign::POS, 0x15).get_val();
+    T neg_snan_0x15 = FPBits::signaling_nan(Sign::NEG, 0x15).get_val();
+
     EXPECT_TRUE(funcWrapper(func, aNaN, aNaN));
     EXPECT_TRUE(funcWrapper(func, sNaN, sNaN));
 
diff --git a/libc/test/src/math/smoke/scalblnbf16_test.cpp b/libc/test/src/math/smoke/scalblnbf16_test.cpp
@@ -0,0 +1,14 @@
+//===-- Unittests for scalblnbf16 -----------------------------------------===//
+//
+// 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 "ScalbnTest.h"
+
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/math/scalblnbf16.h"
+
+LIST_SCALBN_TESTS(bfloat16, long, LIBC_NAMESPACE::scalblnbf16)
diff --git a/libc/test/src/math/smoke/scalbnbf16_test.cpp b/libc/test/src/math/smoke/scalbnbf16_test.cpp
@@ -0,0 +1,14 @@
+//===-- Unittests for scalbnbf16 ------------------------------------------===//
+//
+// 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 "ScalbnTest.h"
+
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/math/scalbnbf16.h"
+
+LIST_SCALBN_TESTS(bfloat16, int, LIBC_NAMESPACE::scalbnbf16)
