[llvm] [Flang-RT] Environment introspection for quadmath.h (PR #130411)
Michael Kruse via llvm-commits
llvm-commits at lists.llvm.org
Sat Mar 8 04:15:51 PST 2025
https://github.com/Meinersbur created https://github.com/llvm/llvm-project/pull/130411
When compiling Flang-RT with Clang, query Clang for the GCC installation it uses. If found, create `quadmath_wrapper.h` that points to the `quadmath.h` of that GCC installation.
`quadmath.h` is only available when compiling with gcc, but Clang has not equivalent. It is available into gcc's installation resource dir (in constrast to a system-wide indirectory such as `/usr/include` or `/usr/local/include`) and therefore not available to any compiler other than the gcc of that installation. quadmath may also be a different OS package than gcc itself, so it is not necessarily presesent.
Clang actually already appropriates a GCC installation for its libraries such as libc such that `libquadmath.a` is already found, but it does not do so for the include paths. Because adding that directory to the header search path may have wise-reaching consquences, we create only a wrapper header that points to the real `quadmath.h` in the same GCC installation that Clang uses.
>From 74fc2b5adf9018c8415b59d4a2865149b11eff99 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Sat, 8 Mar 2025 12:58:09 +0100
Subject: [PATCH] System introspection for quadmath
---
flang-rt/CMakeLists.txt | 47 +++++++++++++++++++++++++++-
flang-rt/cmake/clang_gcc_root.cpp | 3 ++
flang-rt/cmake/quadmath_wrapper.h.in | 9 ++++++
flang-rt/lib/quadmath/CMakeLists.txt | 3 +-
flang-rt/lib/quadmath/complex-math.h | 2 +-
flang-rt/lib/quadmath/math-entries.h | 2 +-
6 files changed, 61 insertions(+), 5 deletions(-)
create mode 100644 flang-rt/cmake/clang_gcc_root.cpp
create mode 100644 flang-rt/cmake/quadmath_wrapper.h.in
diff --git a/flang-rt/CMakeLists.txt b/flang-rt/CMakeLists.txt
index 9f890a015621a..bc16ef4523410 100644
--- a/flang-rt/CMakeLists.txt
+++ b/flang-rt/CMakeLists.txt
@@ -252,6 +252,49 @@ 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 +316,9 @@ 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.
diff --git a/flang-rt/cmake/clang_gcc_root.cpp b/flang-rt/cmake/clang_gcc_root.cpp
new file mode 100644
index 0000000000000..52b490a10a0af
--- /dev/null
+++ b/flang-rt/cmake/clang_gcc_root.cpp
@@ -0,0 +1,3 @@
+int main() {
+ return 0;
+}
\ No newline at end of file
diff --git a/flang-rt/cmake/quadmath_wrapper.h.in b/flang-rt/cmake/quadmath_wrapper.h.in
new file mode 100644
index 0000000000000..c29358efcdb0d
--- /dev/null
+++ b/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 ${FLANG_RT_INCLUDE_QUADMATH_H}
diff --git a/flang-rt/lib/quadmath/CMakeLists.txt b/flang-rt/lib/quadmath/CMakeLists.txt
index 4f113216b42c8..eaf8202d7bce9 100644
--- a/flang-rt/lib/quadmath/CMakeLists.txt
+++ b/flang-rt/lib/quadmath/CMakeLists.txt
@@ -78,8 +78,7 @@ target_include_directories(FortranFloat128MathILib INTERFACE
if (FLANG_RUNTIME_F128_MATH_LIB)
if (${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
diff --git a/flang-rt/lib/quadmath/complex-math.h b/flang-rt/lib/quadmath/complex-math.h
index 424ed84da4e01..b76bf03732938 100644
--- a/flang-rt/lib/quadmath/complex-math.h
+++ b/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)
diff --git a/flang-rt/lib/quadmath/math-entries.h b/flang-rt/lib/quadmath/math-entries.h
index 6e47f32cc8a43..91ad80c8197f4 100644
--- a/flang-rt/lib/quadmath/math-entries.h
+++ b/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)
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