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[Support] Add LLVM_IS_UNALIGNED_ACCESS_FAST. 

llvm-svn: 174271
This commit is contained in:
Michael J. Spencer 2013-02-03 10:48:31 +00:00
parent 8901bb66fb
commit 39678d836c
2 changed files with 29 additions and 4 deletions
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13
llvm/include/llvm/Support/Compiler.h
View File

@ -311,4 +311,17 @@
# define LLVM_MEMORY_SANITIZER_BUILD 0
#endif
/// \macro LLVM_IS_UNALIGNED_ACCESS_FAST
/// \brief Is unaligned memory access fast on the host machine.
///
/// Don't specialize on alignment for platforms where unaligned memory accesses
/// generates the same code as aligned memory accesses for common types.
#if defined(_M_AMD64) || defined(_M_IX86) || defined(__amd64) || \
defined(__amd64__) || defined(__x86_64) || defined(__x86_64__) || \
defined(_X86_) || defined(__i386) || defined(__i386__)
# define LLVM_IS_UNALIGNED_ACCESS_FAST 1
#else
# define LLVM_IS_UNALIGNED_ACCESS_FAST 0
#endif
#endif

20
llvm/lib/Object/ELFObjectFile.cpp
View File

@ -27,30 +27,42 @@ ObjectFile *ObjectFile::createELFObjectFile(MemoryBuffer *Object) {
1ULL << CountTrailingZeros_64(uintptr_t(Object->getBufferStart()));
if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB)
#if !LLVM_IS_UNALIGNED_ACCESS_FAST
if (MaxAlignment >= 4)
return new ELFObjectFile<ELFType<support::little, 4, false> >(Object, ec);
else if (MaxAlignment >= 2)
else
#endif
if (MaxAlignment >= 2)
return new ELFObjectFile<ELFType<support::little, 2, false> >(Object, ec);
else
llvm_unreachable("Invalid alignment for ELF file!");
else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB)
#if !LLVM_IS_UNALIGNED_ACCESS_FAST
if (MaxAlignment >= 4)
return new ELFObjectFile<ELFType<support::big, 4, false> >(Object, ec);
else if (MaxAlignment >= 2)
else
#endif
if (MaxAlignment >= 2)
return new ELFObjectFile<ELFType<support::big, 2, false> >(Object, ec);
else
llvm_unreachable("Invalid alignment for ELF file!");
else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB)
#if !LLVM_IS_UNALIGNED_ACCESS_FAST
if (MaxAlignment >= 8)
return new ELFObjectFile<ELFType<support::big, 8, true> >(Object, ec);
else if (MaxAlignment >= 2)
else
#endif
if (MaxAlignment >= 2)
return new ELFObjectFile<ELFType<support::big, 2, true> >(Object, ec);
else
llvm_unreachable("Invalid alignment for ELF file!");
else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
#if !LLVM_IS_UNALIGNED_ACCESS_FAST
if (MaxAlignment >= 8)
return new ELFObjectFile<ELFType<support::little, 8, true> >(Object, ec);
else if (MaxAlignment >= 2)
else
#endif
if (MaxAlignment >= 2)
return new ELFObjectFile<ELFType<support::little, 2, true> >(Object, ec);
else
llvm_unreachable("Invalid alignment for ELF file!");