[libc] Proof of concept of aliasing long double math functions.

Author: lntue

libc/cmake/modules/LLVMLibCArchitectures.cmake

@@ -150,6 +150,7 @@ if(LIBC_TARGET_ARCHITECTURE STREQUAL "arm")
   set(LIBC_TARGET_ARCHITECTURE_IS_ARM TRUE)
 elseif(LIBC_TARGET_ARCHITECTURE STREQUAL "aarch64")
   set(LIBC_TARGET_ARCHITECTURE_IS_AARCH64 TRUE)
+  set(LIBC_TARGET_LONG_DOUBLE_IS_FLOAT128 TRUE)
 elseif(LIBC_TARGET_ARCHITECTURE STREQUAL "x86_64")
   set(LIBC_TARGET_ARCHITECTURE_IS_X86_64 TRUE)
 elseif(LIBC_TARGET_ARCHITECTURE STREQUAL "i386")

libc/cmake/modules/LLVMLibCCompileOptionRules.cmake

@@ -118,6 +118,8 @@ function(_get_common_compile_options output_var flags)
   if(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
     list(APPEND compile_options "-fpie")
 
+    list(APPEND compile_options "-DLIBC_ALIAS_LONG_DOUBLE")
+
     if(LLVM_LIBC_FULL_BUILD)
       # Only add -ffreestanding flag in non-GPU full build mode.
       if(NOT LIBC_TARGET_OS_IS_GPU)

libc/src/math/CMakeLists.txt

@@ -7,24 +7,31 @@ function(add_math_entrypoint_object name)
   # We prefer machine specific implementation if available. Hence we check
   # that first and return early if we are able to add an alias target for the
   # machine specific implementation.
-  get_fq_target_name("${LIBC_TARGET_ARCHITECTURE}.${name}" fq_machine_specific_target_name)
+  if(NOT ARGN)
+    set(alias_entrypoint ${name})
+  else()
+    message(STATUS "Banananana ${name} ${ARGN}")
+    set(alias_entrypoint ${ARGN})
+  endif()
+
+  get_fq_target_name("${LIBC_TARGET_ARCHITECTURE}.${alias_entrypoint}" fq_machine_specific_target_name)
   if(TARGET ${fq_machine_specific_target_name})
     add_entrypoint_object(
       ${name}
       ALIAS
       DEPENDS
-        .${LIBC_TARGET_ARCHITECTURE}.${name}
+        .${LIBC_TARGET_ARCHITECTURE}.${alias_entrypoint}
     )
     return()
   endif()
 
-  get_fq_target_name("generic.${name}" fq_generic_target_name)
+  get_fq_target_name("generic.${alias_entrypoint}" fq_generic_target_name)
   if(TARGET ${fq_generic_target_name})
     add_entrypoint_object(
       ${name}
       ALIAS
       DEPENDS
-        .generic.${name}
+        .generic.${alias_entrypoint}
     )
     return()
   endif()
@@ -40,6 +47,20 @@ function(add_math_entrypoint_object name)
   )
 endfunction()
 
+function(add_long_double_math_entrypoint_object name)
+  get_fq_target_name(${name} fq_double_math_target)
+  get_fq_target_name("${name}l" fq_long_double_math_target)
+  get_fq_target_name("${name}f128" fq_float128_math_target)
+
+  if(LIBC_TARGET_LONG_DOUBLE_IS_DOUBLE)
+    add_math_entrypoint_object("${name}l" "${name}")
+  elseif(LIBC_TARGET_LONG_DOUBLE_IS_FLOAT128)
+    add_math_entrypoint_object("${name}l" "${name}f128")
+  else()
+    add_math_entrypoint_object("${name}l")
+  endif()
+endfunction()
+
 add_math_entrypoint_object(acos)
 add_math_entrypoint_object(acosf)
 add_math_entrypoint_object(acosf16)
@@ -88,9 +109,9 @@ add_math_entrypoint_object(ceilf128)
 
 add_math_entrypoint_object(copysign)
 add_math_entrypoint_object(copysignf)
-add_math_entrypoint_object(copysignl)
 add_math_entrypoint_object(copysignf16)
 add_math_entrypoint_object(copysignf128)
+add_long_double_math_entrypoint_object(copysign)
 
 add_math_entrypoint_object(cos)
 add_math_entrypoint_object(cosf)

libc/src/math/generic/copysign.cpp

@@ -10,6 +10,7 @@
 #include "src/__support/FPUtil/ManipulationFunctions.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
@@ -22,3 +23,14 @@ LLVM_LIBC_FUNCTION(double, copysign, (double x, double y)) {
 }
 
 } // namespace LIBC_NAMESPACE_DECL
+
+#if defined(LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64) &&                              \
+    defined(LIBC_ALIAS_LONG_DOUBLE)
+#include "src/math/copysignl.h"
+
+namespace LIBC_NAMESPACE_DECL {
+decltype(LIBC_NAMESPACE::copysignl) copysignl [[gnu::alias("copysignl")]];
+asm("copysignl = copysign");
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64

libc/src/math/generic/copysignf128.cpp

@@ -18,3 +18,14 @@ LLVM_LIBC_FUNCTION(float128, copysignf128, (float128 x, float128 y)) {
 }
 
 } // namespace LIBC_NAMESPACE_DECL
+
+#if defined(LIBC_TYPES_LONG_DOUBLE_IS_FLOAT128) &&                             \
+    defined(LIBC_ALIAS_LONG_DOUBLE)
+#include "src/math/copysignl.h"
+
+namespace LIBC_NAMESPACE_DECL {
+decltype(LIBC_NAMESPACE::copysignl) copysignl [[gnu::alias("copysignl")]];
+asm("copysignl = copysignf128");
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_LONG_DOUBLE_IS_FLOAT128

libc/src/math/generic/copysignl.cpp

@@ -10,6 +10,11 @@
 #include "src/__support/FPUtil/ManipulationFunctions.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+#if !(defined(LIBC_ALIAS_LONG_DOUBLE) &&                                       \
+      (defined(LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64) ||                           \
+       defined(LIBC_TYPES_LONG_DOUBLE_IS_FLOAT128)))
 
 namespace LIBC_NAMESPACE_DECL {
 
@@ -18,3 +23,5 @@ LLVM_LIBC_FUNCTION(long double, copysignl, (long double x, long double y)) {
 }
 
 } // namespace LIBC_NAMESPACE_DECL
+
+#endif