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[ADT] Use CMake to detect host endianness (NFC) #164054

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[ADT] Use CMake to detect host endianness (NFC) #164054

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9 changes: 9 additions & 0 deletions llvm/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -1079,6 +1079,15 @@ if(NOT LLVM_ENABLE_NEW_PASS_MANAGER)
" no longer supported.")
endif()

# Determine host endianness.
if(CMAKE_CXX_BYTE_ORDER STREQUAL "BIG_ENDIAN")
set(LLVM_HOST_IS_BIG_ENDIAN 1)
elseif(CMAKE_CXX_BYTE_ORDER STREQUAL "LITTLE_ENDIAN")
set(LLVM_HOST_IS_BIG_ENDIAN 0)
else()
message(FATAL_ERROR "Unsupported CMAKE_CXX_BYTE_ORDER: ${CMAKE_CXX_BYTE_ORDER}")
endif()

include(HandleLLVMOptions)

######
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29 changes: 2 additions & 27 deletions llvm/include/llvm/ADT/bit.h
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Expand Up @@ -14,6 +14,7 @@
#ifndef LLVM_ADT_BIT_H
#define LLVM_ADT_BIT_H

#include "llvm/Config/config.h"
#include "llvm/Support/Compiler.h"
#include <cstddef> // for std::size_t
#include <cstdint>
Expand All @@ -28,32 +29,6 @@
#include <cstdlib> // for _byteswap_{ushort,ulong,uint64}
#endif

#if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__) || \
defined(__Fuchsia__) || defined(__EMSCRIPTEN__) || defined(__NetBSD__) || \
defined(__OpenBSD__) || defined(__DragonFly__) || defined(__managarm__)
#include <endian.h>
#elif defined(_AIX)
#include <sys/machine.h>
#elif defined(__sun)
/* Solaris provides _BIG_ENDIAN/_LITTLE_ENDIAN selector in sys/types.h */
#include <sys/types.h>
#define BIG_ENDIAN 4321
#define LITTLE_ENDIAN 1234
#if defined(_BIG_ENDIAN)
#define BYTE_ORDER BIG_ENDIAN
#else
#define BYTE_ORDER LITTLE_ENDIAN
#endif
#elif defined(__MVS__)
#define BIG_ENDIAN 4321
#define LITTLE_ENDIAN 1234
#define BYTE_ORDER BIG_ENDIAN
#else
#if !defined(BYTE_ORDER) && !defined(_WIN32)
#include <machine/endian.h>
#endif
#endif

#ifdef _MSC_VER
// Declare these intrinsics manually rather including intrin.h. It's very
// expensive, and bit.h is popular via MathExtras.h.
Expand All @@ -71,7 +46,7 @@ namespace llvm {
enum class endianness {
big,
little,
#if defined(BYTE_ORDER) && defined(BIG_ENDIAN) && BYTE_ORDER == BIG_ENDIAN
#if LLVM_HOST_IS_BIG_ENDIAN
native = big
#else
native = little
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3 changes: 3 additions & 0 deletions llvm/include/llvm/Config/config.h.cmake
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Expand Up @@ -10,6 +10,9 @@
/* Bug report URL. */
#define BUG_REPORT_URL "${BUG_REPORT_URL}"

/* Define to 1 if the host is a big endian machine, and to 0 otherwise. */
#cmakedefine01 LLVM_HOST_IS_BIG_ENDIAN

/* Define to 1 to enable backtraces, and to 0 otherwise. */
#cmakedefine01 ENABLE_BACKTRACES

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