[llvm] [APFloat] Add exp functions for single and double using exp/expf implementations from LLVM libc. (PR #190667)
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Mon Apr 6 14:11:07 PDT 2026
https://github.com/lntue updated https://github.com/llvm/llvm-project/pull/190667
>From 6f6980abe4a29340e54726b2076c6a3a92363e65 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 1/2] [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 da012596cca93..93ce760b81637 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -698,6 +698,10 @@ 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 a2c68233fd253..4dd2cc220c862 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -401,7 +401,12 @@ 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 566a1eafb1a04cd95a6a8e191b2b45703caf36a2 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 2/2] 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:
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