[libc-commits] [libc] [libc] add shared subtf3 builtin (PR #205669)
via libc-commits
libc-commits at lists.llvm.org
Wed Jun 24 13:51:53 PDT 2026
https://github.com/hulxv created https://github.com/llvm/llvm-project/pull/205669
Re-exposes LLVM-libc's `__subtf3` as `shared::subtf3` for reuse by compiler-rt's builtins.
Stacked change - merge these first:
- #200094
>From 9a0bb04b42e141693e7b5c6fbfe5623f1beb08b0 Mon Sep 17 00:00:00 2001
From: hulxv <hulxxv at gmail.com>
Date: Thu, 28 May 2026 03:01:10 +0300
Subject: [PATCH 1/4] [libc] introduce shared compiler-rt builtins
---
libc/include/llvm-libc-macros/float-macros.h | 6 ++++
libc/shared/builtins.h | 16 +++++++++
libc/shared/builtins/addtf3.h | 35 ++++++++++++++++++++
libc/src/__support/CMakeLists.txt | 1 +
libc/src/__support/FPUtil/dyadic_float.h | 3 ++
libc/src/__support/builtins/CMakeLists.txt | 9 +++++
libc/src/__support/builtins/addtf3.h | 32 ++++++++++++++++++
libc/test/shared/CMakeLists.txt | 10 ++++++
libc/test/shared/shared_builtins_test.cpp | 29 ++++++++++++++++
9 files changed, 141 insertions(+)
create mode 100644 libc/shared/builtins.h
create mode 100644 libc/shared/builtins/addtf3.h
create mode 100644 libc/src/__support/builtins/CMakeLists.txt
create mode 100644 libc/src/__support/builtins/addtf3.h
create mode 100644 libc/test/shared/shared_builtins_test.cpp
diff --git a/libc/include/llvm-libc-macros/float-macros.h b/libc/include/llvm-libc-macros/float-macros.h
index a25ef60a293d3..38a3a771cca54 100644
--- a/libc/include/llvm-libc-macros/float-macros.h
+++ b/libc/include/llvm-libc-macros/float-macros.h
@@ -9,6 +9,12 @@
#ifndef LLVM_LIBC_MACROS_FLOAT_MACROS_H
#define LLVM_LIBC_MACROS_FLOAT_MACROS_H
+// __has_builtin is a Clang extension; GCC < 10 doesn't define it, which
+// turns a bare `#if __has_builtin(...)` into a preprocessor syntax error.
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
#ifndef FLT_RADIX
#define FLT_RADIX __FLT_RADIX__
#endif // FLT_RADIX
diff --git a/libc/shared/builtins.h b/libc/shared/builtins.h
new file mode 100644
index 0000000000000..157b6622cbcff
--- /dev/null
+++ b/libc/shared/builtins.h
@@ -0,0 +1,16 @@
+//===-- Compiler-runtime builtin primitives ---------------------*- 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_SHARED_BUILTINS_H
+#define LLVM_LIBC_SHARED_BUILTINS_H
+
+#include "libc_common.h"
+
+#include "builtins/addtf3.h"
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_H
diff --git a/libc/shared/builtins/addtf3.h b/libc/shared/builtins/addtf3.h
new file mode 100644
index 0000000000000..9c39e6e9a8406
--- /dev/null
+++ b/libc/shared/builtins/addtf3.h
@@ -0,0 +1,35 @@
+//===-- Shared __addtf3 function -------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This header exposes LLVM-libc's __addtf3 implementation as shared::addtf3
+// so that it can be reused by other LLVM projects, such as compiler-rt's
+// builtins library.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_ADDTF3_H
+#define LLVM_LIBC_SHARED_BUILTINS_ADDTF3_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/addtf3.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::addtf3;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_ADDTF3_H
diff --git a/libc/src/__support/CMakeLists.txt b/libc/src/__support/CMakeLists.txt
index 9d08b4bcf7303..c09ca012c3594 100644
--- a/libc/src/__support/CMakeLists.txt
+++ b/libc/src/__support/CMakeLists.txt
@@ -472,6 +472,7 @@ add_subdirectory(wchar)
add_subdirectory(wctype)
add_subdirectory(math)
+add_subdirectory(builtins)
if(LIBC_COMPILER_HAS_EXT_VECTOR_TYPE)
add_subdirectory(mathvec)
endif()
diff --git a/libc/src/__support/FPUtil/dyadic_float.h b/libc/src/__support/FPUtil/dyadic_float.h
index 7e4ea2f1a81be..d99a14f35f38e 100644
--- a/libc/src/__support/FPUtil/dyadic_float.h
+++ b/libc/src/__support/FPUtil/dyadic_float.h
@@ -415,6 +415,9 @@ template <size_t Bits> struct DyadicFloat {
if constexpr (cpp::is_same_v<T, bfloat16>
#if defined(LIBC_TYPES_HAS_FLOAT16) && !defined(__LIBC_USE_FLOAT16_CONVERSION)
|| cpp::is_same_v<T, float16>
+#endif
+#if defined(LIBC_TYPES_HAS_FLOAT128)
+ || cpp::is_same_v<T, float128>
#endif
)
return generic_as<T, ShouldSignalExceptions>();
diff --git a/libc/src/__support/builtins/CMakeLists.txt b/libc/src/__support/builtins/CMakeLists.txt
new file mode 100644
index 0000000000000..c4982887d0a7c
--- /dev/null
+++ b/libc/src/__support/builtins/CMakeLists.txt
@@ -0,0 +1,9 @@
+add_header_library(
+ addtf3
+ HDRS
+ addtf3.h
+ DEPENDS
+ libc.include.llvm-libc-types.float128
+ libc.src.__support.FPUtil.generic.add_sub
+ libc.src.__support.macros.config
+)
diff --git a/libc/src/__support/builtins/addtf3.h b/libc/src/__support/builtins/addtf3.h
new file mode 100644
index 0000000000000..129ad2a81e827
--- /dev/null
+++ b/libc/src/__support/builtins/addtf3.h
@@ -0,0 +1,32 @@
+//===-- Implementation header for __addtf3 ----------------------*- 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___SUPPORT_BUILTINS_ADDTF3_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_ADDTF3_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "src/__support/FPUtil/generic/add_sub.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Mirrors the compiler-rt __addtf3 ABI: a + b at float128 precision.
+LIBC_INLINE float128 addtf3(float128 x, float128 y) {
+ return fputil::generic::add<float128>(x, y);
+}
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_ADDTF3_H
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 7a5c3a369c2fc..0f8027e2e0057 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -814,6 +814,16 @@ add_fp_unittest(
)
endif() # LIBC_TEST_SKIP_SHARED_MATH_TESTS
+add_fp_unittest(
+ shared_builtins_test
+ SUITE
+ libc-shared-tests
+ SRCS
+ shared_builtins_test.cpp
+ DEPENDS
+ libc.src.__support.builtins.addtf3
+)
+
add_fp_unittest(
shared_str_to_num_test
SUITE
diff --git a/libc/test/shared/shared_builtins_test.cpp b/libc/test/shared/shared_builtins_test.cpp
new file mode 100644
index 0000000000000..67d40b349cef3
--- /dev/null
+++ b/libc/test/shared/shared_builtins_test.cpp
@@ -0,0 +1,29 @@
+//===-- Unittests for shared builtins -------------------------------------===//
+//
+// 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 "shared/builtins.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcSharedBuiltinsTest, AllFloat) {
+ // TODO: assertions for shared::*sf3 builtins.
+}
+
+TEST(LlvmLibcSharedBuiltinsTest, AllDouble) {
+ // TODO: assertions for shared::*df3 builtins.
+}
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+TEST(LlvmLibcSharedBuiltinsTest, AllFloat128) {
+ namespace shared = LIBC_NAMESPACE::shared;
+
+ EXPECT_FP_EQ(float128(3.0), shared::addtf3(float128(1.0), float128(2.0)));
+}
+
+#endif // LIBC_TYPES_HAS_FLOAT128
>From 8a3828ae0484b9e8df38518fe12df718c9de5c17 Mon Sep 17 00:00:00 2001
From: hulxv <hulxxv at gmail.com>
Date: Thu, 11 Jun 2026 15:48:50 +0300
Subject: [PATCH 2/4] correct the header
---
libc/shared/builtins/addtf3.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/libc/shared/builtins/addtf3.h b/libc/shared/builtins/addtf3.h
index 9c39e6e9a8406..33534beeb91c7 100644
--- a/libc/shared/builtins/addtf3.h
+++ b/libc/shared/builtins/addtf3.h
@@ -1,15 +1,15 @@
-//===-- Shared __addtf3 function -------------------------------*- 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
//
//===----------------------------------------------------------------------===//
-//
-// This header exposes LLVM-libc's __addtf3 implementation as shared::addtf3
-// so that it can be reused by other LLVM projects, such as compiler-rt's
-// builtins library.
-//
+///
+/// \file
+/// This header exposes LLVM-libc's __addtf3 implementation as shared::addtf3
+/// so that it can be reused by compiler-rt's builtins.
+///
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SHARED_BUILTINS_ADDTF3_H
>From 0fea0cd53236c37ad58f9cc54d440ec0ad102823 Mon Sep 17 00:00:00 2001
From: hulxv <hulxxv at gmail.com>
Date: Tue, 23 Jun 2026 22:48:07 +0300
Subject: [PATCH 3/4] header
---
libc/shared/builtins.h | 8 +++++++-
libc/src/__support/builtins/addtf3.h | 8 +++++++-
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/libc/shared/builtins.h b/libc/shared/builtins.h
index 157b6622cbcff..338755314d309 100644
--- a/libc/shared/builtins.h
+++ b/libc/shared/builtins.h
@@ -1,10 +1,16 @@
-//===-- Compiler-runtime builtin primitives ---------------------*- 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
//
//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header aggregates LLVM-libc's shared compiler-rt builtins so that
+/// they can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SHARED_BUILTINS_H
#define LLVM_LIBC_SHARED_BUILTINS_H
diff --git a/libc/src/__support/builtins/addtf3.h b/libc/src/__support/builtins/addtf3.h
index 129ad2a81e827..f33036f53ec30 100644
--- a/libc/src/__support/builtins/addtf3.h
+++ b/libc/src/__support/builtins/addtf3.h
@@ -1,10 +1,16 @@
-//===-- Implementation header for __addtf3 ----------------------*- 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
//
//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header exposes LLVM-libc's __addtf3 implementation as
+/// builtins::addtf3 so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_ADDTF3_H
#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_ADDTF3_H
>From 5b0f8cf2c1d877710f242e262750f712e26faf58 Mon Sep 17 00:00:00 2001
From: hulxv <hulxxv at gmail.com>
Date: Wed, 24 Jun 2026 22:32:52 +0300
Subject: [PATCH 4/4] [libc] add shared subtf3 builtin
---
libc/shared/builtins.h | 1 +
libc/shared/builtins/subtf3.h | 35 ++++++++++++++++++++
libc/src/__support/builtins/CMakeLists.txt | 10 ++++++
libc/src/__support/builtins/subtf3.h | 38 ++++++++++++++++++++++
libc/test/shared/shared_builtins_test.cpp | 10 ++++++
5 files changed, 94 insertions(+)
create mode 100644 libc/shared/builtins/subtf3.h
create mode 100644 libc/src/__support/builtins/subtf3.h
diff --git a/libc/shared/builtins.h b/libc/shared/builtins.h
index 338755314d309..0bb156131423d 100644
--- a/libc/shared/builtins.h
+++ b/libc/shared/builtins.h
@@ -18,5 +18,6 @@
#include "libc_common.h"
#include "builtins/addtf3.h"
+#include "builtins/subtf3.h"
#endif // LLVM_LIBC_SHARED_BUILTINS_H
diff --git a/libc/shared/builtins/subtf3.h b/libc/shared/builtins/subtf3.h
new file mode 100644
index 0000000000000..a7cecef8b0479
--- /dev/null
+++ b/libc/shared/builtins/subtf3.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 __subtf3 implementation as shared::subtf3 so
+/// that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_BUILTINS_SUBTF3_H
+#define LLVM_LIBC_SHARED_BUILTINS_SUBTF3_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "shared/libc_common.h"
+#include "src/__support/builtins/subtf3.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using builtins::subtf3;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SHARED_BUILTINS_SUBTF3_H
diff --git a/libc/src/__support/builtins/CMakeLists.txt b/libc/src/__support/builtins/CMakeLists.txt
index c4982887d0a7c..d3d1d65babce8 100644
--- a/libc/src/__support/builtins/CMakeLists.txt
+++ b/libc/src/__support/builtins/CMakeLists.txt
@@ -7,3 +7,13 @@ add_header_library(
libc.src.__support.FPUtil.generic.add_sub
libc.src.__support.macros.config
)
+
+add_header_library(
+ subtf3
+ HDRS
+ subtf3.h
+ DEPENDS
+ libc.include.llvm-libc-types.float128
+ libc.src.__support.FPUtil.generic.add_sub
+ libc.src.__support.macros.config
+)
diff --git a/libc/src/__support/builtins/subtf3.h b/libc/src/__support/builtins/subtf3.h
new file mode 100644
index 0000000000000..bd758cce0f5f6
--- /dev/null
+++ b/libc/src/__support/builtins/subtf3.h
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 __subtf3 implementation as builtins::subtf3
+/// so that it can be reused by compiler-rt's builtins.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_BUILTINS_SUBTF3_H
+#define LLVM_LIBC_SRC___SUPPORT_BUILTINS_SUBTF3_H
+
+#include "include/llvm-libc-types/float128.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+#include "src/__support/FPUtil/generic/add_sub.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace builtins {
+
+// Subtraction at float128 precision; mirrors compiler-rt's __subtf3.
+LIBC_INLINE float128 subtf3(float128 x, float128 y) {
+ return fputil::generic::sub<float128>(x, y);
+}
+
+} // namespace builtins
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT128
+
+#endif // LLVM_LIBC_SRC___SUPPORT_BUILTINS_SUBTF3_H
diff --git a/libc/test/shared/shared_builtins_test.cpp b/libc/test/shared/shared_builtins_test.cpp
index 67d40b349cef3..d2d9c71d4f4fd 100644
--- a/libc/test/shared/shared_builtins_test.cpp
+++ b/libc/test/shared/shared_builtins_test.cpp
@@ -27,3 +27,13 @@ TEST(LlvmLibcSharedBuiltinsTest, AllFloat128) {
}
#endif // LIBC_TYPES_HAS_FLOAT128
+
+#ifdef LIBC_TYPES_HAS_FLOAT128
+
+TEST(LlvmLibcSharedBuiltinsTest, Subtf3) {
+ namespace shared = LIBC_NAMESPACE::shared;
+
+ EXPECT_FP_EQ(float128(2.0), shared::subtf3(float128(5.0), float128(3.0)));
+}
+
+#endif // LIBC_TYPES_HAS_FLOAT128
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