[Flang-RT] Environment introspection for quadmath.h

flang-rt/CMakeLists.txt

@@ -252,6 +252,46 @@ set(HAVE_BACKTRACE ${Backtrace_FOUND})
 set(BACKTRACE_HEADER ${Backtrace_HEADER})
 
 
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  if (NOT DEFINED FLANG_RT_GCC_RESOURCE_DIR)
+    set(FLANG_RT_GCC_RESOURCE_DIR "FLANG_RT_GCC_RESOURCE_DIR-NOTFOUND")
+    execute_process(
+      COMMAND "${CMAKE_CXX_COMPILER}" -v -c "${FLANG_RT_SOURCE_DIR}/cmake/clang_gcc_root.cpp" ${CMAKE_CXX_FLAGS} -###
+      ERROR_FILE "${CMAKE_CURRENT_BINARY_DIR}/clang_gcc_root_result"
+    )
+    file(STRINGS "${CMAKE_CURRENT_BINARY_DIR}/clang_gcc_root_result" _errorresult)
+    foreach (_line IN LISTS _errorresult)
+      string(REGEX MATCH
+        "^Selected GCC installation: (.+)$"
+        _match
+        "${_line}")
+      if (CMAKE_MATCH_1)
+        set(FLANG_RT_GCC_RESOURCE_DIR "${CMAKE_MATCH_1}")
+        message(STATUS "Found GCC installation selected by Clang: ${FLANG_RT_GCC_RESOURCE_DIR}")
+        break()
+      endif ()
+    endforeach ()
+    set(FLANG_RT_GCC_RESOURCE_DIR "${FLANG_RT_GCC_RESOURCE_DIR}" CACHE INTERNAL "Path to GCC's resource dir selected by Clang" FORCE)
+  endif ()
+endif ()
+
+check_include_file("quadmath.h" FOUND_QUADMATH_H)
+if (FOUND_QUADMATH_H)
+  message(STATUS "quadmath.h found without additional include paths")
+  set(FLANG_RT_INCLUDE_QUADMATH_H "<quadmath.h>")
+elseif (FLANG_RT_GCC_RESOURCE_DIR)
+  cmake_push_check_state()
+    list(APPEND CMAKE_REQUIRED_INCLUDES "${FLANG_RT_GCC_RESOURCE_DIR}/include")
+    check_include_file("quadmath.h" FOUND_GCC_QUADMATH_H)
+  cmake_pop_check_state()
+  if (FOUND_GCC_QUADMATH_H)
+    message(STATUS "quadmath.h found in Clang's selected GCC installation")
+    set(FLANG_RT_INCLUDE_QUADMATH_H "\"${FLANG_RT_GCC_RESOURCE_DIR}/include/quadmath.h\"")
+  endif ()
+endif ()
+
+
+
 #####################
 # Build Preparation #
 #####################
@@ -273,7 +313,9 @@ set(CMAKE_CXX_STANDARD_REQUIRED YES)
 
 
 configure_file(cmake/config.h.cmake.in config.h)
-
+if (FLANG_RT_INCLUDE_QUADMATH_H)
+  configure_file("cmake/quadmath_wrapper.h.in" "${FLANG_RT_BINARY_DIR}/quadmath_wrapper.h")
+endif ()
 
 # The bootstrap build will create a phony target with the same as the top-level
 # directory ("flang-rt") and delegate it to the runtimes build dir.

flang-rt/cmake/clang_gcc_root.cpp

@@ -0,0 +1 @@
+int main() { return 0; }

flang-rt/cmake/quadmath_wrapper.h.in

@@ -0,0 +1,9 @@
+/*===-- cmake/quadmath_wrapper.h.in ---------------------=-----------*- C -*-===
+ *
+ * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+ * See https://llvm.org/LICENSE.txt for license information.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ *
+ *===----------------------------------------------------------------------===*/
+
+#include ${FLANG_RT_INCLUDE_QUADMATH_H}

flang-rt/lib/quadmath/CMakeLists.txt

@@ -78,8 +78,7 @@ target_include_directories(FortranFloat128MathILib INTERFACE
 
 if (FLANG_RUNTIME_F128_MATH_LIB)
   if (${FLANG_RUNTIME_F128_MATH_LIB} STREQUAL "libquadmath")
-    check_include_file(quadmath.h FOUND_QUADMATH_HEADER)
-    if(FOUND_QUADMATH_HEADER)
+    if(FLANG_RT_INCLUDE_QUADMATH_H)
       add_compile_definitions(HAS_QUADMATHLIB)
     else()
       message(FATAL_ERROR

flang-rt/lib/quadmath/complex-math.h

@@ -13,7 +13,7 @@
 #include "flang/Runtime/entry-names.h"
 
 #if HAS_QUADMATHLIB
-#include "quadmath.h"
+#include "quadmath_wrapper.h"
 #define CAbs(x) cabsq(x)
 #define CAcos(x) cacosq(x)
 #define CAcosh(x) cacoshq(x)

flang-rt/lib/quadmath/math-entries.h

@@ -112,7 +112,7 @@ DEFINE_FALLBACK_F128(Yn)
 
 #if HAS_QUADMATHLIB
 // Define wrapper callers for libquadmath.
-#include "quadmath.h"
+#include "quadmath_wrapper.h"
 DEFINE_SIMPLE_ALIAS(Abs, fabsq)
 DEFINE_SIMPLE_ALIAS(Acos, acosq)
 DEFINE_SIMPLE_ALIAS(Acosh, acoshq)