[llvm] [APFloat] Add exp functions for single and double using exp/expf implementations from LLVM libc. (PR #190667)
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Sat Apr 18 16:26:09 PDT 2026
https://github.com/lntue updated https://github.com/llvm/llvm-project/pull/190667
>From 3b431aca4f7ab00584e3c22aae5119ba8b71d481 Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue.h at gmail.com>
Date: Mon, 6 Apr 2026 20:01:21 +0000
Subject: [PATCH 1/5] [APFloat] Add exp functions for single and double using
exp/expf implementations from LLVM libc.
This reapplies #143959 with some changes:
Only support default rounding modes for now.
---
llvm/CMakeLists.txt | 4 +++
llvm/include/llvm/ADT/APFloat.h | 5 +++
llvm/lib/Support/APFloat.cpp | 25 ++++++++++++++
llvm/lib/Support/CMakeLists.txt | 5 +++
llvm/unittests/ADT/APFloatTest.cpp | 53 ++++++++++++++++++++++++++++++
5 files changed, 92 insertions(+)
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 6001928f92e37..4509fbaba1d25 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -700,6 +700,10 @@ endif()
set(LLVM_ENABLE_Z3_SOLVER_DEFAULT "${Z3_FOUND}")
+include(FindLibcCommonUtils)
+if(NOT TARGET llvm-libc-common-utilities)
+ message(FATAL_ERROR "LLVM libc is not found at ${libc_path}.")
+endif()
if( LLVM_TARGETS_TO_BUILD STREQUAL "all" )
set( LLVM_TARGETS_TO_BUILD ${LLVM_ALL_TARGETS} )
diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index f1645729c115c..cfbb02fd63936 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -1730,6 +1730,11 @@ inline APFloat maximumnum(const APFloat &A, const APFloat &B) {
return A < B ? B : A;
}
+/// Implement IEEE 754-2019 exp functions
+LLVM_READONLY
+inline APFloat exp(const APFloat &X,
+ RoundingMode RM = APFloat::rmNearestTiesToEven);
+
inline raw_ostream &operator<<(raw_ostream &OS, const APFloat &V) {
V.print(OS);
return OS;
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index 47c712125f044..c6c1779420d43 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -29,6 +29,13 @@
#include <cstring>
#include <limits.h>
+// Shared headers from LLVM libc
+// Make sure to add ${LLVM_SOURCE_DIR}/../libc to include directories.
+#define LIBC_NAMESPACE __llvm_libc_apfloat
+#define LIBC_MATH (LIBC_MATH_NO_ERRNO | LIBC_MATH_NO_EXCEPT)
+
+#include "shared/math.h"
+
#define APFLOAT_DISPATCH_ON_SEMANTICS(METHOD_CALL) \
do { \
if (usesLayout<IEEEFloat>(getSemantics())) \
@@ -6071,6 +6078,24 @@ APFloat::Storage &APFloat::Storage::operator=(APFloat::Storage &&RHS) {
return *this;
}
+// TODO: Support other rounding modes when LLVM libc math implement static
+// roundings.
+APFloat exp(const APFloat &X, RoundingMode rounding_mode) {
+ if (rounding_mode == APFloatBase::rmNearestTiesToEven) {
+ if (APFloat::SemanticsToEnum(X.getSemantics()) ==
+ APFloatBase::S_IEEEsingle) {
+ float result = LIBC_NAMESPACE::shared::expf(X.convertToFloat());
+ return APFloat(result);
+ }
+ if (APFloat::SemanticsToEnum(X.getSemantics()) ==
+ APFloatBase::S_IEEEdouble) {
+ double result = LIBC_NAMESPACE::shared::exp(X.convertToDouble());
+ return APFloat(result);
+ }
+ }
+ llvm_unreachable("Unexpected semantics");
+}
+
} // namespace llvm
#undef APFLOAT_DISPATCH_ON_SEMANTICS
diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index e8d505f218b69..ab8ac2ac33065 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -400,7 +400,12 @@ endif()
target_include_directories(LLVMSupport
PRIVATE
${LLVM_THIRD_PARTY_DIR}/siphash/include
+ ${LLVM_SOURCE_DIR}/../libc
)
+if(NOT MSVC)
+ target_compile_options(LLVMSupport PRIVATE "-Wno-c99-extensions") # _Complex warnings.
+endif()
+
# SupportLSP depends on Support and therefore must be included afterwards.
add_subdirectory(LSP)
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 8ff3efe64c29b..23da1ee83bd16 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -10206,4 +10206,57 @@ TEST(APFloatTest, isValidArbitraryFPFormat) {
EXPECT_FALSE(APFloat::isValidArbitraryFPFormat("unknown"));
}
+TEST(APFloatTest, expf) {
+ // exp(+-0) = 1.
+ EXPECT_EQ(1.0f, llvm::exp(APFloat(0.0f)).convertToFloat());
+ EXPECT_EQ(1.0f, llvm::exp(APFloat(-0.0f)).convertToFloat());
+ // exp(+Inf) = +Inf.
+ EXPECT_EQ(std::numeric_limits<float>::infinity(),
+ llvm::exp(APFloat::getInf(APFloat::IEEEsingle(), false))
+ .convertToFloat());
+ // exp(-Inf) = 0.
+ EXPECT_EQ(
+ 0.0f,
+ llvm::exp(APFloat::getInf(APFloat::IEEEsingle(), true)).convertToFloat());
+ // exp(NaN) = NaN.
+ EXPECT_TRUE(llvm::exp(APFloat::getNaN(APFloat::IEEEsingle())).isNaN());
+ // exp(1)
+ EXPECT_EQ(0x1.5bf0a8p1f, llvm::exp(APFloat(1.0f)).convertToFloat());
+ // exp(float max)
+ EXPECT_EQ(std::numeric_limits<float>::infinity(),
+ llvm::exp(APFloat::getLargest(APFloat::IEEEsingle(), false))
+ .convertToFloat());
+ // exp(min_denormal)
+ EXPECT_EQ(1.0f, llvm::exp(APFloat::getSmallest(APFloat::IEEEsingle(), false))
+ .convertToFloat());
+ // exp(-1)
+ EXPECT_EQ(0x1.78b564p-2f, llvm::exp(APFloat(-1.0f)).convertToFloat());
+}
+
+TEST(APFloatTest, exp) {
+ // exp(+-0) = 1.
+ EXPECT_EQ(1.0, llvm::exp(APFloat(0.0)).convertToDouble());
+ EXPECT_EQ(1.0, llvm::exp(APFloat(-0.0)).convertToDouble());
+ // exp(+Inf) = +Inf.
+ EXPECT_EQ(std::numeric_limits<double>::infinity(),
+ llvm::exp(APFloat::getInf(APFloat::IEEEdouble(), false))
+ .convertToDouble());
+ // exp(-Inf) = 0.
+ EXPECT_EQ(0.0, llvm::exp(APFloat::getInf(APFloat::IEEEdouble(), true))
+ .convertToDouble());
+ // exp(NaN) = NaN.
+ EXPECT_TRUE(llvm::exp(APFloat::getNaN(APFloat::IEEEdouble())).isNaN());
+ // exp(1)
+ EXPECT_EQ(0x1.5bf0a8b145769p1, llvm::exp(APFloat(1.0)).convertToDouble());
+ // exp(float max)
+ EXPECT_EQ(std::numeric_limits<double>::infinity(),
+ llvm::exp(APFloat::getLargest(APFloat::IEEEdouble(), false))
+ .convertToDouble());
+ // exp(min_denormal)
+ EXPECT_EQ(1.0, llvm::exp(APFloat::getSmallest(APFloat::IEEEdouble(), false))
+ .convertToDouble());
+ // exp(-1)
+ EXPECT_EQ(0x1.78b56362cef38p-2, llvm::exp(APFloat(-1.0f)).convertToDouble());
+}
+
} // namespace
>From da6fefb5c06894c6fe3d812e2bf9f3c469cd9330 Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue.h at gmail.com>
Date: Mon, 6 Apr 2026 21:10:39 +0000
Subject: [PATCH 2/5] Re-add AMDGPULibCalls fix.
---
llvm/lib/Target/AMDGPU/AMDGPULibCalls.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Target/AMDGPU/AMDGPULibCalls.cpp b/llvm/lib/Target/AMDGPU/AMDGPULibCalls.cpp
index a26ad67458359..e0c2bddb65caa 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULibCalls.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPULibCalls.cpp
@@ -1868,7 +1868,7 @@ bool AMDGPULibCalls::evaluateScalarMathFunc(const FuncInfo &FInfo,
return true;
case AMDGPULibFunc::EI_EXP:
- Res0 = APFloat{exp(opr0)};
+ Res0 = APFloat{std::exp(opr0)};
return true;
case AMDGPULibFunc::EI_EXP2:
>From 68708b15cbfbd214f0ab2d7ae83949ed031bd97f Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue.h at gmail.com>
Date: Mon, 6 Apr 2026 22:20:55 +0000
Subject: [PATCH 3/5] Remove `inline` from declaration.
---
llvm/include/llvm/ADT/APFloat.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index cfbb02fd63936..393e74b6cfea5 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -1732,8 +1732,7 @@ inline APFloat maximumnum(const APFloat &A, const APFloat &B) {
/// Implement IEEE 754-2019 exp functions
LLVM_READONLY
-inline APFloat exp(const APFloat &X,
- RoundingMode RM = APFloat::rmNearestTiesToEven);
+APFloat exp(const APFloat &X, RoundingMode RM = APFloat::rmNearestTiesToEven);
inline raw_ostream &operator<<(raw_ostream &OS, const APFloat &V) {
V.print(OS);
>From 2f34084394ea58295378aa6df0134defe3c27f57 Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue.h at gmail.com>
Date: Mon, 6 Apr 2026 23:08:32 +0000
Subject: [PATCH 4/5] Fix data type in exp test.
---
llvm/unittests/ADT/APFloatTest.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 23da1ee83bd16..467425ac91c7c 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -10256,7 +10256,7 @@ TEST(APFloatTest, exp) {
EXPECT_EQ(1.0, llvm::exp(APFloat::getSmallest(APFloat::IEEEdouble(), false))
.convertToDouble());
// exp(-1)
- EXPECT_EQ(0x1.78b56362cef38p-2, llvm::exp(APFloat(-1.0f)).convertToDouble());
+ EXPECT_EQ(0x1.78b56362cef38p-2, llvm::exp(APFloat(-1.0)).convertToDouble());
}
} // namespace
>From 8c2b2b5dacc41a98f8d5cf089c616f06bce0c8bc Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue.h at gmail.com>
Date: Sat, 18 Apr 2026 23:25:39 +0000
Subject: [PATCH 5/5] Add tests with denormal outputs.
---
llvm/unittests/ADT/APFloatTest.cpp | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 467425ac91c7c..5884a57022d14 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -10231,6 +10231,8 @@ TEST(APFloatTest, expf) {
.convertToFloat());
// exp(-1)
EXPECT_EQ(0x1.78b564p-2f, llvm::exp(APFloat(-1.0f)).convertToFloat());
+ // exp(-90)
+ EXPECT_EQ(0x1.1d85p-130f, llvm::exp(APFloat(-90.0f)).convertToFloat());
}
TEST(APFloatTest, exp) {
@@ -10257,6 +10259,9 @@ TEST(APFloatTest, exp) {
.convertToDouble());
// exp(-1)
EXPECT_EQ(0x1.78b56362cef38p-2, llvm::exp(APFloat(-1.0)).convertToDouble());
+ // exp(-710)
+ EXPECT_EQ(0x1.9c017e9459e18p-1025,
+ llvm::exp(APFloat(-710.0)).convertToDouble());
}
} // namespace
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