[compiler-rt][builtins] libc-backed floating-point extend/trunct builtins (#209984)

Add libc-backed floating-point extend/truncate builtins

Part of #197824

compiler-rt/lib/builtins/CMakeLists.txt

@@ -243,6 +243,27 @@ set(GENERIC_TF_SOURCES
   trunctfsf2.c
 )
 
+# Implement extended-precision builtins, assuming long double is 80 bits.
+# long double is not 80 bits on Android or MSVC.
+set(x86_80_BIT_SOURCES
+  divxc3.c
+  extendhfxf2.c
+  extendxftf2.c
+  fixxfdi.c
+  fixxfti.c
+  fixunsxfdi.c
+  fixunsxfsi.c
+  fixunsxfti.c
+  floatdixf.c
+  floattixf.c
+  floatundixf.c
+  floatuntixf.c
+  mulxc3.c
+  powixf2.c
+  trunctfxf2.c
+  truncxfhf2.c
+)
+
 option(COMPILER_RT_USE_LIBC_MATH
       "Use LLVM libc math routines for floating-point builtins" OFF)
 
@@ -270,6 +291,10 @@ if(COMPILER_RT_USE_LIBC_MATH)
   use_libc_builtin(GENERIC_SOURCES    divdf3)
   use_libc_builtin(GENERIC_SOURCES    divsf3)
   use_libc_builtin(GENERIC_TF_SOURCES divtf3)
+  use_libc_builtin(GENERIC_TF_SOURCES extenddftf2)
+  use_libc_builtin(GENERIC_SOURCES    extendsfdf2)
+  use_libc_builtin(GENERIC_TF_SOURCES extendsftf2)
+  use_libc_builtin(x86_80_BIT_SOURCES extendxftf2)
   use_libc_builtin(GENERIC_SOURCES    muldf3)
   use_libc_builtin(GENERIC_SOURCES    mulsf3)
   use_libc_builtin(GENERIC_TF_SOURCES multf3)
@@ -278,6 +303,10 @@ if(COMPILER_RT_USE_LIBC_MATH)
   use_libc_builtin(GENERIC_SOURCES    subdf3)
   use_libc_builtin(GENERIC_SOURCES    subsf3)
   use_libc_builtin(GENERIC_TF_SOURCES subtf3)
+  use_libc_builtin(GENERIC_SOURCES    truncdfsf2)  
+  use_libc_builtin(GENERIC_TF_SOURCES trunctfdf2)
+  use_libc_builtin(GENERIC_TF_SOURCES trunctfsf2)
+  use_libc_builtin(x86_80_BIT_SOURCES trunctfxf2)
 endif()
 
 option(COMPILER_RT_EXCLUDE_ATOMIC_BUILTIN
@@ -349,27 +378,6 @@ if (NOT MSVC)
   )
 endif ()
 
-# Implement extended-precision builtins, assuming long double is 80 bits.
-# long double is not 80 bits on Android or MSVC.
-set(x86_80_BIT_SOURCES
-  divxc3.c
-  extendhfxf2.c
-  extendxftf2.c
-  fixxfdi.c
-  fixxfti.c
-  fixunsxfdi.c
-  fixunsxfsi.c
-  fixunsxfti.c
-  floatdixf.c
-  floattixf.c
-  floatundixf.c
-  floatuntixf.c
-  mulxc3.c
-  powixf2.c
-  trunctfxf2.c
-  truncxfhf2.c
-)
-
 if (NOT MSVC)
   set(x86_64_SOURCES
     ${GENERIC_SOURCES}

compiler-rt/lib/builtins/extenddftf2.cpp

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __extenddftf2, extend double to float128,
+/// on top of LLVM-libc's shared::extenddftf2.
+///
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#include "fp_libc_config.h"
+#include "shared/builtins/extenddftf2.h"
+
+#ifdef CRT_HAS_TF_MODE
+extern "C" COMPILER_RT_ABI tf_float __extenddftf2(double a) {
+  return LIBC_NAMESPACE::shared::extenddftf2(a);
+}
+#endif

compiler-rt/lib/builtins/extendsfdf2.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __extendsfdf2, extend float to double, on
+/// top of LLVM-libc's shared::extendsfdf2.
+///
+//===----------------------------------------------------------------------===//
+
+#include "shared/builtins/extendsfdf2.h"
+#include "fp_libc_config.h"
+#include "int_lib.h"
+
+extern "C" COMPILER_RT_ABI double __extendsfdf2(float a) {
+  return LIBC_NAMESPACE::shared::extendsfdf2(a);
+}

compiler-rt/lib/builtins/extendsftf2.cpp

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __extendsftf2, extend float to float128,
+/// on top of LLVM-libc's shared::extendsftf2.
+///
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#include "fp_libc_config.h"
+#include "shared/builtins/extendsftf2.h"
+
+#ifdef CRT_HAS_TF_MODE
+extern "C" COMPILER_RT_ABI tf_float __extendsftf2(float a) {
+  return LIBC_NAMESPACE::shared::extendsftf2(a);
+}
+#endif

compiler-rt/lib/builtins/extendxftf2.cpp

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __extendxftf2, extend long double to
+/// float128, on top of LLVM-libc's shared::extendxftf2.
+///
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#include "fp_libc_config.h"
+#include "shared/builtins/extendxftf2.h"
+
+#if defined(CRT_HAS_TF_MODE) && __LDBL_MANT_DIG__ == 64 && defined(__x86_64__)
+extern "C" COMPILER_RT_ABI tf_float __extendxftf2(xf_float a) {
+  return LIBC_NAMESPACE::shared::extendxftf2(a);
+}
+#endif

compiler-rt/lib/builtins/truncdfsf2.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __truncdfsf2, truncate double to float,
+/// on top of LLVM-libc's shared::truncdfsf2.
+///
+//===----------------------------------------------------------------------===//
+
+#include "shared/builtins/truncdfsf2.h"
+#include "fp_libc_config.h"
+#include "int_lib.h"
+
+extern "C" COMPILER_RT_ABI float __truncdfsf2(double a) {
+  return LIBC_NAMESPACE::shared::truncdfsf2(a);
+}

compiler-rt/lib/builtins/trunctfdf2.cpp

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __trunctfdf2, truncate float128 to
+/// double, on top of LLVM-libc's shared::trunctfdf2.
+///
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#include "fp_libc_config.h"
+#include "shared/builtins/trunctfdf2.h"
+
+#ifdef CRT_HAS_TF_MODE
+extern "C" COMPILER_RT_ABI double __trunctfdf2(tf_float a) {
+  return LIBC_NAMESPACE::shared::trunctfdf2(a);
+}
+#endif

compiler-rt/lib/builtins/trunctfsf2.cpp

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __trunctfsf2, truncate float128 to float,
+/// on top of LLVM-libc's shared::trunctfsf2.
+///
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#include "fp_libc_config.h"
+#include "shared/builtins/trunctfsf2.h"
+
+#ifdef CRT_HAS_TF_MODE
+extern "C" COMPILER_RT_ABI float __trunctfsf2(tf_float a) {
+  return LIBC_NAMESPACE::shared::trunctfsf2(a);
+}
+#endif

compiler-rt/lib/builtins/trunctfxf2.cpp

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements compiler-rt's __trunctfxf2, truncate float128 to long
+/// double, on top of LLVM-libc's shared::trunctfxf2.
+///
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+
+#include "fp_libc_config.h"
+#include "shared/builtins/trunctfxf2.h"
+
+#if defined(CRT_HAS_TF_MODE) && __LDBL_MANT_DIG__ == 64 && defined(__x86_64__)
+extern "C" COMPILER_RT_ABI xf_float __trunctfxf2(tf_float a) {
+  return LIBC_NAMESPACE::shared::trunctfxf2(a);
+}
+#endif

libc/shared/builtins.h

@@ -23,6 +23,10 @@
 #include "builtins/divdf3.h"
 #include "builtins/divsf3.h"
 #include "builtins/divtf3.h"
+#include "builtins/extenddftf2.h"
+#include "builtins/extendsfdf2.h"
+#include "builtins/extendsftf2.h"
+#include "builtins/extendxftf2.h"
 #include "builtins/muldf3.h"
 #include "builtins/mulsf3.h"
 #include "builtins/multf3.h"
@@ -31,5 +35,9 @@
 #include "builtins/subdf3.h"
 #include "builtins/subsf3.h"
 #include "builtins/subtf3.h"
+#include "builtins/truncdfsf2.h"
+#include "builtins/trunctfdf2.h"
+#include "builtins/trunctfsf2.h"
+#include "builtins/trunctfxf2.h"
 
 #endif // LLVM_LIBC_SHARED_BUILTINS_H

libc/shared/builtins/extenddftf2.h

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extenddftf2 implementation as
+/// shared::extenddftf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_EXTENDDFTF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_EXTENDDFTF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/extenddftf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::extenddftf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_EXTENDDFTF2_H

libc/shared/builtins/extendsfdf2.h

@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extendsfdf2 implementation as
+/// shared::extendsfdf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_EXTENDSFDF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_EXTENDSFDF2_H
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/extendsfdf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::extendsfdf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_EXTENDSFDF2_H

libc/shared/builtins/extendsftf2.h

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extendsftf2 implementation as
+/// shared::extendsftf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_EXTENDSFTF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_EXTENDSFTF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/extendsftf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::extendsftf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_EXTENDSFTF2_H

libc/shared/builtins/extendxftf2.h

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extendxftf2 implementation as
+/// shared::extendxftf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_EXTENDXFTF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_EXTENDXFTF2_H
+
+#include "include/llvm-libc-types/float128.h"
+#include "src/__support/macros/properties/types.h"
+
+#if defined(LIBC_TYPES_HAS_FLOAT128) &&                                        \
+    defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/extendxftf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::extendxftf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128 && LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_EXTENDXFTF2_H

libc/shared/builtins/truncdfsf2.h

@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __truncdfsf2 implementation as
+/// shared::truncdfsf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_TRUNCDFSF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_TRUNCDFSF2_H
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/truncdfsf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::truncdfsf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_TRUNCDFSF2_H

libc/shared/builtins/trunctfdf2.h

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __trunctfdf2 implementation as
+/// shared::trunctfdf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_TRUNCTFDF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_TRUNCTFDF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/trunctfdf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::trunctfdf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_TRUNCTFDF2_H

libc/shared/builtins/trunctfsf2.h

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __trunctfsf2 implementation as
+/// shared::trunctfsf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_TRUNCTFSF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_TRUNCTFSF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/trunctfsf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::trunctfsf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_TRUNCTFSF2_H

libc/shared/builtins/trunctfxf2.h

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __trunctfxf2 implementation as
+/// shared::trunctfxf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_TRUNCTFXF2_H
+#define LLVM_LIBC_SHARED_BUILTINS_TRUNCTFXF2_H
+
+#include "include/llvm-libc-types/float128.h"
+#include "src/__support/macros/properties/types.h"
+
+#if defined(LIBC_TYPES_HAS_FLOAT128) &&                                        \
+    defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/trunctfxf2.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::trunctfxf2;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128 && LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_TRUNCTFXF2_H

libc/src/__support/builtins/CMakeLists.txt

@@ -1,3 +1,19 @@
+add_header_library(
+  fpconvert_helper
+  HDRS
+    fpconvert_helper.h
+  DEPENDS
+    libc.hdr.fenv_macros
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.CPP.bit
+    libc.src.__support.CPP.type_traits
+    libc.src.__support.FPUtil.dyadic_float
+    libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.macros.attributes
+    libc.src.__support.macros.config
+)
+
 add_header_library(
   addtf3
   HDRS
@@ -127,3 +143,83 @@ add_header_library(
     libc.src.__support.FPUtil.generic.div
     libc.src.__support.macros.config
 )
+
+add_header_library(
+  extendsftf2
+  HDRS
+    extendsftf2.h
+  DEPENDS
+    libc.include.llvm-libc-types.float128
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+)
+
+add_header_library(
+  extenddftf2
+  HDRS
+    extenddftf2.h
+  DEPENDS
+    libc.include.llvm-libc-types.float128
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+)
+
+add_header_library(
+  extendxftf2
+  HDRS
+    extendxftf2.h
+  DEPENDS
+    libc.include.llvm-libc-types.float128
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
+add_header_library(
+  trunctfdf2
+  HDRS
+    trunctfdf2.h
+  DEPENDS
+    libc.include.llvm-libc-types.float128
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+)
+
+add_header_library(
+  trunctfsf2
+  HDRS
+    trunctfsf2.h
+  DEPENDS
+    libc.include.llvm-libc-types.float128
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+)
+
+add_header_library(
+  trunctfxf2
+  HDRS
+    trunctfxf2.h
+  DEPENDS
+    libc.include.llvm-libc-types.float128
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
+add_header_library(
+  extendsfdf2
+  HDRS
+    extendsfdf2.h
+  DEPENDS
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+)
+
+add_header_library(
+  truncdfsf2
+  HDRS
+    truncdfsf2.h
+  DEPENDS
+    libc.src.__support.builtins.fpconvert_helper
+    libc.src.__support.macros.config
+)

libc/src/__support/builtins/extenddftf2.h

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extenddftf2 implementation as
+/// builtins::extenddftf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDDFTF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDDFTF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Extend double to float128; mirrors compiler-rt's __extenddftf2.
+LIBC_INLINE float128 extenddftf2(double x) { return fpconvert<float128>(x); }
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDDFTF2_H

libc/src/__support/builtins/extendsfdf2.h

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extendsfdf2 implementation as
+/// builtins::extendsfdf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDSFDF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDSFDF2_H
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Extend float to double; mirrors compiler-rt's __extendsfdf2.
+LIBC_INLINE double extendsfdf2(float x) { return fpconvert<double>(x); }
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDSFDF2_H

libc/src/__support/builtins/extendsftf2.h

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extendsftf2 implementation as
+/// builtins::extendsftf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDSFTF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDSFTF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Extend float to float128; mirrors compiler-rt's __extendsftf2.
+LIBC_INLINE float128 extendsftf2(float x) { return fpconvert<float128>(x); }
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDSFTF2_H

libc/src/__support/builtins/extendxftf2.h

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __extendxftf2 implementation as
+/// builtins::extendxftf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDXFTF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDXFTF2_H
+
+#include "include/llvm-libc-types/float128.h"
+#include "src/__support/macros/properties/types.h"
+
+#if defined(LIBC_TYPES_HAS_FLOAT128) &&                                        \
+    defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Extend long double to float128; mirrors compiler-rt's __extendxftf2.
+LIBC_INLINE float128 extendxftf2(long double x) {
+  return fpconvert<float128>(x);
+}
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128 && LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_EXTENDXFTF2_H

libc/src/__support/builtins/fpconvert_helper.h

@@ -0,0 +1,83 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Shared float-to-float extend/truncate conversions, rounding to nearest
+/// (ties to even) when narrowing.  These mirror compiler-rt's __extend<a><b>2 /
+/// __trunc<a><b>2 builtins, so they can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_FPCONVERT_HELPER_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_FPCONVERT_HELPER_H
+
+#include "hdr/fenv_macros.h"
+#include "src/__support/CPP/algorithm.h"
+#include "src/__support/CPP/bit.h"
+#include "src/__support/CPP/type_traits.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/dyadic_float.h"
+#include "src/__support/macros/attributes.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// TODO: use fputil::cast after adding Float128/64/32/16 classes currently, we
+// are using this helper to avoid an infinity loop that happens because
+// fputil::cast is calling the builtins if the target doesn't have FPU.
+//
+// assembly (each body below compiles to a self-call):
+//   // double f(float128 x) { return cast<double>(x); }
+//   trunc_tf_df:  callq __trunctfdf2@PLT
+//   // float128 g(double x) { return cast<float128>(x); }
+//   ext_df_tf:    jmp   __extenddftf2@PLT   // TAILCALL
+
+// Convert the floating-point value x from From to To (extend or truncate).
+// Narrowing rounds to nearest, ties to even; mirrors compiler-rt __extend* /
+// __trunc*.
+template <typename To, typename From>
+LIBC_INLINE constexpr To fpconvert(From x) {
+  using FromBits = fputil::FPBits<From>;
+  using ToBits = fputil::FPBits<To>;
+  using ToStorageType = typename ToBits::StorageType;
+
+  FromBits x_bits(x);
+
+  if constexpr (cpp::is_same_v<To, From>)
+    return x;
+
+  if (x_bits.is_nan()) {
+    typename FromBits::StorageType x_frac = x_bits.get_mantissa();
+    if constexpr (ToBits::FRACTION_LEN >= FromBits::FRACTION_LEN) {
+      ToStorageType to_frac =
+          static_cast<ToStorageType>(x_frac)
+          << (ToBits::FRACTION_LEN - FromBits::FRACTION_LEN);
+      return ToBits::signaling_nan(x_bits.sign(), to_frac).get_val();
+    }
+    ToStorageType to_frac = static_cast<ToStorageType>(
+        x_frac >> (FromBits::FRACTION_LEN - ToBits::FRACTION_LEN));
+    return ToBits::quiet_nan(x_bits.sign(), to_frac).get_val();
+  }
+
+  if (x_bits.is_inf())
+    return ToBits::inf(x_bits.sign()).get_val();
+
+  // Zero and subnormals fall through: DyadicFloat(x) gives a zero mantissa for
+  // zero, which as<To>() maps back to a correctly-signed zero.
+  constexpr size_t MAX_FRACTION_LEN =
+      cpp::max(ToBits::FRACTION_LEN, FromBits::FRACTION_LEN);
+  fputil::DyadicFloat<cpp::bit_ceil(MAX_FRACTION_LEN)> xd(x);
+  return xd.template as<To, /*ShouldSignalExceptions=*/true>();
+}
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_FPCONVERT_HELPER_H

libc/src/__support/builtins/truncdfsf2.h

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __truncdfsf2 implementation as
+/// builtins::truncdfsf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCDFSF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCDFSF2_H
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Truncate double to float; mirrors compiler-rt's __truncdfsf2.
+LIBC_INLINE float truncdfsf2(double x) { return fpconvert<float>(x); }
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCDFSF2_H

libc/src/__support/builtins/trunctfdf2.h

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __trunctfdf2 implementation as
+/// builtins::trunctfdf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFDF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFDF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Truncate float128 to double; mirrors compiler-rt's __trunctfdf2.
+LIBC_INLINE double trunctfdf2(float128 x) { return fpconvert<double>(x); }
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFDF2_H

libc/src/__support/builtins/trunctfsf2.h

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __trunctfsf2 implementation as
+/// builtins::trunctfsf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFSF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFSF2_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Truncate float128 to float; mirrors compiler-rt's __trunctfsf2.
+LIBC_INLINE float trunctfsf2(float128 x) { return fpconvert<float>(x); }
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFSF2_H

libc/src/__support/builtins/trunctfxf2.h

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __trunctfxf2 implementation as
+/// builtins::trunctfxf2 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFXF2_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFXF2_H
+
+#include "include/llvm-libc-types/float128.h"
+#include "src/__support/macros/properties/types.h"
+
+#if defined(LIBC_TYPES_HAS_FLOAT128) &&                                        \
+    defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
+
+#include "src/__support/builtins/fpconvert_helper.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Truncate float128 to long double; mirrors compiler-rt's __trunctfxf2.
+LIBC_INLINE long double trunctfxf2(float128 x) {
+  return fpconvert<long double>(x);
+}
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128 && LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_TRUNCTFXF2_H

libc/test/shared/CMakeLists.txt

@@ -834,6 +834,10 @@ add_fp_unittest(
     libc.src.__support.builtins.divdf3
     libc.src.__support.builtins.divsf3
     libc.src.__support.builtins.divtf3
+    libc.src.__support.builtins.extenddftf2
+    libc.src.__support.builtins.extendsfdf2
+    libc.src.__support.builtins.extendsftf2
+    libc.src.__support.builtins.extendxftf2
     libc.src.__support.builtins.muldf3
     libc.src.__support.builtins.mulsf3
     libc.src.__support.builtins.multf3
@@ -842,6 +846,10 @@ add_fp_unittest(
     libc.src.__support.builtins.subdf3
     libc.src.__support.builtins.subsf3
     libc.src.__support.builtins.subtf3
+    libc.src.__support.builtins.truncdfsf2
+    libc.src.__support.builtins.trunctfdf2
+    libc.src.__support.builtins.trunctfsf2
+    libc.src.__support.builtins.trunctfxf2
 )
 
 add_fp_unittest(

libc/test/shared/shared_builtins_test.cpp

@@ -38,3 +38,25 @@ TEST(LlvmLibcSharedBuiltinsTest, QuadPrecisionArithmtic) {
 }
 
 #endif // LIBC_TYPES_HAS_FLOAT128
+
+TEST(LlvmLibcSharedBuiltinsTest, ExtendConversion) {
+  EXPECT_FP_EQ(1.5, shared::extendsfdf2(1.5f));
+#ifdef LIBC_TYPES_HAS_FLOAT128
+  EXPECT_FP_EQ(float128(1.5), shared::extenddftf2(1.5));
+  EXPECT_FP_EQ(float128(1.5), shared::extendsftf2(1.5f));
+#ifdef LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+  EXPECT_FP_EQ(float128(1.5), shared::extendxftf2(1.5L));
+#endif // LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+#endif // LIBC_TYPES_HAS_FLOAT128
+}
+
+TEST(LlvmLibcSharedBuiltinsTest, TruncateConversion) {
+  EXPECT_FP_EQ(1.5f, shared::truncdfsf2(1.5));
+#ifdef LIBC_TYPES_HAS_FLOAT128
+  EXPECT_FP_EQ(1.5, shared::trunctfdf2(float128(1.5)));
+  EXPECT_FP_EQ(1.5f, shared::trunctfsf2(float128(1.5)));
+#ifdef LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+  EXPECT_FP_EQ(1.5L, shared::trunctfxf2(float128(1.5)));
+#endif // LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
+#endif // LIBC_TYPES_HAS_FLOAT128
+}