Enable logf128 constant folding for hosts with 128bit floats (#96287)

Hosts which support a float size of 128 bits can benefit from constant
fp128 folding.

Author: MDevereau

llvm/CMakeLists.txt

@@ -560,8 +560,6 @@ set(LLVM_USE_STATIC_ZSTD FALSE CACHE BOOL "Use static version of zstd. Can be TR
 
 set(LLVM_ENABLE_CURL "OFF" CACHE STRING "Use libcurl for the HTTP client if available. Can be ON, OFF, or FORCE_ON")
 
-set(LLVM_HAS_LOGF128 "OFF" CACHE STRING "Use logf128 to constant fold fp128 logarithm calls. Can be ON, OFF, or FORCE_ON")
-
 set(LLVM_ENABLE_HTTPLIB "OFF" CACHE STRING "Use cpp-httplib HTTP server library if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")

llvm/cmake/config-ix.cmake

@@ -247,17 +247,6 @@ else()
   set(HAVE_LIBEDIT 0)
 endif()
 
-if(LLVM_HAS_LOGF128)
-  include(CheckCXXSymbolExists)
-  check_cxx_symbol_exists(logf128 math.h HAS_LOGF128)
-
-  if(LLVM_HAS_LOGF128 STREQUAL FORCE_ON AND NOT HAS_LOGF128)
-    message(FATAL_ERROR "Failed to configure logf128")
-  endif()
-
-  set(LLVM_HAS_LOGF128 "${HAS_LOGF128}")
-endif()
-
 # function checks
 check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
 find_package(Backtrace)
@@ -271,6 +260,12 @@ if(C_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW)
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror=unguarded-availability-new")
 endif()
 
+check_cxx_symbol_exists(logf128 cmath HAS_LOGF128)
+if(HAS_LOGF128)
+    set(LLVM_HAS_LOGF128 On)
+    add_compile_definitions(HAS_LOGF128)
+endif()
+
 # Determine whether we can register EH tables.
 check_symbol_exists(__register_frame "${CMAKE_CURRENT_LIST_DIR}/unwind.h" HAVE_REGISTER_FRAME)
 check_symbol_exists(__deregister_frame "${CMAKE_CURRENT_LIST_DIR}/unwind.h" HAVE_DEREGISTER_FRAME)

llvm/include/llvm/ADT/APFloat.h

@@ -378,7 +378,7 @@ class IEEEFloat final : public APFloatBase {
   Expected<opStatus> convertFromString(StringRef, roundingMode);
   APInt bitcastToAPInt() const;
   double convertToDouble() const;
-#ifdef HAS_IEE754_FLOAT128
+#if defined(HAS_IEE754_FLOAT128)
   float128 convertToQuad() const;
 #endif
   float convertToFloat() const;
@@ -1279,7 +1279,7 @@ class APFloat : public APFloatBase {
   /// \pre The APFloat must be built using semantics, that can be represented by
   /// the host float type without loss of precision. It can be IEEEquad and
   /// shorter semantics, like IEEEdouble and others.
-#ifdef HAS_IEE754_FLOAT128
+#if defined(HAS_IEE754_FLOAT128)
   float128 convertToQuad() const;
 #endif
 

llvm/include/llvm/Support/float128.h

@@ -9,18 +9,16 @@
 #ifndef LLVM_FLOAT128
 #define LLVM_FLOAT128
 
+#include <cmath>
+
 namespace llvm {
 
-#if defined(__clang__) && defined(__FLOAT128__) &&                             \
-    defined(__SIZEOF_INT128__) && !defined(__LONG_DOUBLE_IBM128__)
-#define HAS_IEE754_FLOAT128
-typedef __float128 float128;
-#elif defined(__FLOAT128__) && defined(__SIZEOF_INT128__) &&                   \
-    !defined(__LONG_DOUBLE_IBM128__) &&                                        \
-    (defined(__GNUC__) || defined(__GNUG__))
+#ifdef HAS_LOGF128
+#if !defined(__LONG_DOUBLE_IBM128__) && (__SIZEOF_INT128__ == 16)
+typedef decltype(logf128(0.)) float128;
 #define HAS_IEE754_FLOAT128
-typedef _Float128 float128;
 #endif
+#endif // HAS_LOGF128
 
 } // namespace llvm
 #endif // LLVM_FLOAT128

llvm/lib/Analysis/CMakeLists.txt

@@ -161,9 +161,3 @@ add_llvm_component_library(LLVMAnalysis
   Support
   TargetParser
   )
-
-include(CheckCXXSymbolExists)
-check_cxx_symbol_exists(logf128 math.h HAS_LOGF128)
-if(HAS_LOGF128)
- target_compile_definitions(LLVMAnalysis PRIVATE HAS_LOGF128)
-endif()

llvm/lib/Analysis/ConstantFolding.cpp

@@ -1781,7 +1781,7 @@ Constant *ConstantFoldFP(double (*NativeFP)(double), const APFloat &V,
   return GetConstantFoldFPValue(Result, Ty);
 }
 
-#if defined(HAS_IEE754_FLOAT128) && defined(HAS_LOGF128)
+#if defined(HAS_IEE754_FLOAT128)
 Constant *ConstantFoldFP128(float128 (*NativeFP)(float128), const APFloat &V,
                             Type *Ty) {
   llvm_fenv_clearexcept();
@@ -2114,7 +2114,7 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
     if (IntrinsicID == Intrinsic::canonicalize)
       return constantFoldCanonicalize(Ty, Call, U);
 
-#if defined(HAS_IEE754_FLOAT128) && defined(HAS_LOGF128)
+#if defined(HAS_IEE754_FLOAT128)
     if (Ty->isFP128Ty()) {
       if (IntrinsicID == Intrinsic::log) {
         float128 Result = logf128(Op->getValueAPF().convertToQuad());

llvm/lib/Support/APFloat.cpp

@@ -3749,7 +3749,7 @@ double IEEEFloat::convertToDouble() const {
   return api.bitsToDouble();
 }
 
-#ifdef HAS_IEE754_FLOAT128
+#if defined(HAS_IEE754_FLOAT128)
 float128 IEEEFloat::convertToQuad() const {
   assert(semantics == (const llvm::fltSemantics *)&semIEEEquad &&
          "Float semantics are not IEEEquads");
@@ -5406,7 +5406,7 @@ double APFloat::convertToDouble() const {
   return Temp.getIEEE().convertToDouble();
 }
 
-#ifdef HAS_IEE754_FLOAT128
+#if defined(HAS_IEE754_FLOAT128)
 float128 APFloat::convertToQuad() const {
   if (&getSemantics() == (const llvm::fltSemantics *)&semIEEEquad)
     return getIEEE().convertToQuad();