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[Flang] Detect endianness in the preprocessor #132767

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Merged
jhuber6 merged 1 commit into from
Mar 24, 2025
Merged

[Flang] Detect endianness in the preprocessor #132767

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40 changes: 13 additions & 27 deletions flang/cmake/modules/FlangCommon.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -24,30 +24,16 @@ if (FLANG_RUNTIME_F128_MATH_LIB)
add_compile_definitions(FLANG_RUNTIME_F128_MATH_LIB="${FLANG_RUNTIME_F128_MATH_LIB}")
endif()

# The NVPTX target can't emit a binary due to the PTXAS dependency, just
# hard-code this.
if ("${LLVM_RUNTIMES_TARGET}" MATCHES "^nvptx")
add_compile_definitions(FLANG_LITTLE_ENDIAN=1)
else ()
# Check if 128-bit float computations can be done via long double
# Note that '-nostdinc++' might be implied when this code kicks in
# (see 'runtimes/CMakeLists.txt'), so we cannot use 'cfloat' C++ header
# file in the test below.
# Compile it as C.
check_c_source_compiles(
"#include <float.h>
#if LDBL_MANT_DIG != 113
#error LDBL_MANT_DIG != 113
#endif
int main() { return 0; }
"
HAVE_LDBL_MANT_DIG_113)

include(TestBigEndian)
test_big_endian(IS_BIGENDIAN)
if (IS_BIGENDIAN)
add_compile_definitions(FLANG_BIG_ENDIAN=1)
else ()
add_compile_definitions(FLANG_LITTLE_ENDIAN=1)
endif ()
endif ()
# Check if 128-bit float computations can be done via long double
# Note that '-nostdinc++' might be implied when this code kicks in
# (see 'runtimes/CMakeLists.txt'), so we cannot use 'cfloat' C++ header
# file in the test below.
# Compile it as C.
check_c_source_compiles(
"#include <float.h>
#if LDBL_MANT_DIG != 113
#error LDBL_MANT_DIG != 113
#endif
int main() { return 0; }
"
HAVE_LDBL_MANT_DIG_113)
17 changes: 17 additions & 0 deletions flang/include/flang/Common/api-attrs.h
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Expand Up @@ -189,4 +189,21 @@
#define RT_OPTNONE_ATTR
#endif

/* Detect system endianness if it was not explicitly set. */
#if !defined(FLANG_LITTLE_ENDIAN) && !defined(FLANG_BIG_ENDIAN)

/* We always assume Windows is little endian, otherwise use the GCC compatible
* flags. */
#if defined(_MSC_VER) || defined(_WIN32)
#define FLANG_LITTLE_ENDIAN 1
#elif defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
#define FLANG_LITTLE_ENDIAN 1
#elif defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
#define FLANG_BIG_ENDIAN 1
#else
#error "Unknown or unsupported endianness."
#endif

#endif /* !defined(FLANG_LITTLE_ENDIAN) && !defined(FLANG_BIG_ENDIAN) */

#endif /* !FORTRAN_RUNTIME_API_ATTRS_H_ */
1 change: 1 addition & 0 deletions flang/include/flang/Evaluate/common.h
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Expand Up @@ -9,6 +9,7 @@
#ifndef FORTRAN_EVALUATE_COMMON_H_
#define FORTRAN_EVALUATE_COMMON_H_

#include "flang/Common/api-attrs.h"
#include "flang/Common/enum-set.h"
#include "flang/Common/idioms.h"
#include "flang/Common/indirection.h"
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