[libc-commits] [libc] [libc][math][c23] Enable C23 _Float16 math functions on GPUs (PR #99248)

[via libc-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: OverMighty (overmighty)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/99248.diff


2 Files Affected:

- (modified) libc/cmake/modules/CheckCompilerFeatures.cmake (+26-7) 
- (modified) libc/config/gpu/entrypoints.txt (+71) 


``````````diff
diff --git a/libc/cmake/modules/CheckCompilerFeatures.cmake b/libc/cmake/modules/CheckCompilerFeatures.cmake
index a6d793d495c45..361c1e710b187 100644
--- a/libc/cmake/modules/CheckCompilerFeatures.cmake
+++ b/libc/cmake/modules/CheckCompilerFeatures.cmake
@@ -15,6 +15,12 @@ set(
 # Making sure ALL_COMPILER_FEATURES is sorted.
 list(SORT ALL_COMPILER_FEATURES)
 
+# Compiler features that are unavailable on GPU targets with the in-tree Clang.
+set(
+  CPU_ONLY_COMPILER_FEATURES
+    "float128"
+)
+
 # Function to check whether the compiler supports the provided set of features.
 # Usage:
 # compiler_supports(
@@ -65,13 +71,26 @@ foreach(feature IN LISTS ALL_COMPILER_FEATURES)
     set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE)
   endif()
 
-  try_compile(
-    has_feature
-    ${CMAKE_CURRENT_BINARY_DIR}/compiler_features
-    SOURCES ${LIBC_SOURCE_DIR}/cmake/modules/compiler_features/check_${feature}.cpp
-    COMPILE_DEFINITIONS -I${LIBC_SOURCE_DIR} ${compile_options}
-    LINK_OPTIONS ${link_options}
-  )
+  if(LIBC_TARGET_OS_IS_GPU)
+    # CUDA shouldn't be required to build the libc, only to test it, so we can't
+    # try to build CUDA binaries here. Since GPU builds are always compiled with
+    # the in-tree Clang, we just hardcode which compiler features are available
+    # when targeting GPUs.
+    if(feature IN_LIST CPU_ONLY_COMPILER_FEATURES)
+      set(has_feature FALSE)
+    else()
+      set(has_feature TRUE)
+    endif()
+  else()
+    try_compile(
+      has_feature
+      ${CMAKE_CURRENT_BINARY_DIR}/compiler_features
+      SOURCES ${LIBC_SOURCE_DIR}/cmake/modules/compiler_features/check_${feature}.cpp
+      COMPILE_DEFINITIONS -I${LIBC_SOURCE_DIR} ${compile_options}
+      LINK_OPTIONS ${link_options}
+    )
+  endif()
+
   if(has_feature)
     list(APPEND AVAILABLE_COMPILER_FEATURES ${feature})
     if(${feature} STREQUAL "float16")
diff --git a/libc/config/gpu/entrypoints.txt b/libc/config/gpu/entrypoints.txt
index 63228216c85ec..20c97fbbbadc5 100644
--- a/libc/config/gpu/entrypoints.txt
+++ b/libc/config/gpu/entrypoints.txt
@@ -343,6 +343,77 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.truncf
 )
 
+if(LIBC_TYPES_HAS_FLOAT16)
+  list(APPEND TARGET_LIBM_ENTRYPOINTS
+    # math.h C23 _Float16 entrypoints
+    libc.src.math.canonicalizef16
+    libc.src.math.ceilf16
+    libc.src.math.copysignf16
+    libc.src.math.f16add
+    libc.src.math.f16addf
+    libc.src.math.f16addl
+    libc.src.math.f16div
+    libc.src.math.f16divf
+    libc.src.math.f16divl
+    libc.src.math.f16fma
+    libc.src.math.f16fmaf
+    libc.src.math.f16fmal
+    libc.src.math.f16sqrt
+    libc.src.math.f16sqrtf
+    libc.src.math.f16sqrtl
+    libc.src.math.f16sub
+    libc.src.math.f16subf
+    libc.src.math.f16subl
+    libc.src.math.fabsf16
+    libc.src.math.fdimf16
+    libc.src.math.floorf16
+    libc.src.math.fmaxf16
+    libc.src.math.fmaximum_mag_numf16
+    libc.src.math.fmaximum_magf16
+    libc.src.math.fmaximum_numf16
+    libc.src.math.fmaximumf16
+    libc.src.math.fminf16
+    libc.src.math.fminimum_mag_numf16
+    libc.src.math.fminimum_magf16
+    libc.src.math.fminimum_numf16
+    libc.src.math.fminimumf16
+    libc.src.math.fmodf16
+    libc.src.math.frexpf16
+    libc.src.math.fromfpf16
+    libc.src.math.fromfpxf16
+    libc.src.math.getpayloadf16
+    libc.src.math.ilogbf16
+    libc.src.math.ldexpf16
+    libc.src.math.llogbf16
+    libc.src.math.llrintf16
+    libc.src.math.llroundf16
+    libc.src.math.logbf16
+    libc.src.math.lrintf16
+    libc.src.math.lroundf16
+    libc.src.math.modff16
+    libc.src.math.nanf16
+    libc.src.math.nearbyintf16
+    libc.src.math.nextafterf16
+    libc.src.math.nextdownf16
+    libc.src.math.nexttowardf16
+    libc.src.math.nextupf16
+    libc.src.math.remainderf16
+    libc.src.math.remquof16
+    libc.src.math.rintf16
+    libc.src.math.roundevenf16
+    libc.src.math.roundf16
+    libc.src.math.scalblnf16
+    libc.src.math.scalbnf16
+    libc.src.math.setpayloadf16
+    libc.src.math.setpayloadsigf16
+    libc.src.math.totalorderf16
+    libc.src.math.totalordermagf16
+    libc.src.math.truncf16
+    libc.src.math.ufromfpf16
+    libc.src.math.ufromfpxf16
+  )
+endif()
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}

``````````

</details>


https://github.com/llvm/llvm-project/pull/99248