Is there a compelling reason to use __BIGGEST_ALIGNMENT__ over max_align_t?
On Sat, Dec 13, 2014 at 9:51 AM, mats petersson <[email protected]> wrote: > > This is my first attempt for a patch to Clang, so please accept my > apologies for any misconduct with regards to formatting, styling, > content, culture, etc - and I hope that gmail doesn't munge the > patch... > > The idea for this came about when at work (ARM) we discussed some code > that had accidentally aligned it's sub-allocated block to 4 bytes for > a 64-bit type, and got a unaligned access trap. So "how do you know", > and someone found __BIGGEST_ALIGNMENT__ in gcc - but not available for > Clang. So I thought I could add it, to make it a little more > consistent between compilers... > > -- > Mats > > Add a predefined macro reflecting the largest alignment required by > the archiecture, in bytes. This is useful for allocator designs that > need to know the system alignment requirements. It reflects the > TargetInfo.SuitableAlignment, converted to bytes (using CharWidth). > --- > lib/Frontend/InitPreprocessor.cpp | 4 ++++ > test/Preprocessor/init.c | 33 +++++++++++++++++++++++++++++++++ > 2 files changed, 37 insertions(+), 0 deletions(-) > > diff --git a/lib/Frontend/InitPreprocessor.cpp > b/lib/Frontend/InitPreprocessor.cpp > index f4241a9..896277a 100644 > --- a/lib/Frontend/InitPreprocessor.cpp > +++ b/lib/Frontend/InitPreprocessor.cpp > @@ -710,6 +710,10 @@ static void InitializePredefinedMacros(const > TargetInfo &TI, > Builder.defineMacro("__POINTER_WIDTH__", > Twine((int)TI.getPointerWidth(0))); > > + // Define __BIGGEST_ALIGNMENT__ to be compatible with gcc. > + Builder.defineMacro("__BIGGEST_ALIGNMENT__", > + Twine(TI.getSuitableAlign() / TI.getCharWidth()) ); > + > if (!LangOpts.CharIsSigned) > Builder.defineMacro("__CHAR_UNSIGNED__"); > > diff --git a/test/Preprocessor/init.c b/test/Preprocessor/init.c > index 4f32114..924aa5b 100644 > --- a/test/Preprocessor/init.c > +++ b/test/Preprocessor/init.c > @@ -241,6 +241,7 @@ > // AARCH64:#define __ARM_ARCH 8 > // AARCH64:#define __ARM_ARCH_ISA_A64 1 > // AARCH64-NOT:#define __ARM_BIG_ENDIAN 1 > +// AARCH64:#define __BIGGEST_ALIGNMENT__ 8 > // AARCH64:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // AARCH64:#define __CHAR16_TYPE__ unsigned short > // AARCH64:#define __CHAR32_TYPE__ unsigned int > @@ -431,6 +432,7 @@ > // AARCH64-BE:#define __ARM_ARCH 8 > // AARCH64-BE:#define __ARM_ARCH_ISA_A64 1 > // AARCH64-BE:#define __ARM_BIG_ENDIAN 1 > +// AARCH64-BE:#define __BIGGEST_ALIGNMENT__ 8 > // AARCH64-BE:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // AARCH64-BE:#define __CHAR16_TYPE__ unsigned short > // AARCH64-BE:#define __CHAR32_TYPE__ unsigned int > @@ -621,6 +623,7 @@ > // AARCH64-NETBSD:#define __ARM_ARCH 8 > // AARCH64-NETBSD:#define __ARM_ARCH_ISA_A64 1 > // AARCH64-NETBSD-NOT:#define __ARM_BIG_ENDIAN 1 > +// AARCH64-NETBSD:#define __BIGGEST_ALIGNMENT__ 8 > // AARCH64-NETBSD:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // AARCH64-NETBSD:#define __CHAR16_TYPE__ unsigned short > // AARCH64-NETBSD:#define __CHAR32_TYPE__ unsigned int > @@ -812,6 +815,7 @@ > // AARCH64-FREEBSD:#define __ARM_ARCH 8 > // AARCH64-FREEBSD:#define __ARM_ARCH_ISA_A64 1 > // AARCH64-FREEBSD-NOT:#define __ARM_BIG_ENDIAN 1 > +// AARCH64-FREEBSD:#define __BIGGEST_ALIGNMENT__ 8 > // AARCH64-FREEBSD:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // AARCH64-FREEBSD:#define __CHAR16_TYPE__ unsigned short > // AARCH64-FREEBSD:#define __CHAR32_TYPE__ unsigned int > @@ -1003,6 +1007,7 @@ > // ARM:#define __ARMEL__ 1 > // ARM:#define __ARM_ARCH_6J__ 1 > // ARM-NOT:#define __ARM_BIG_ENDIAN 1 > +// ARM:#define __BIGGEST_ALIGNMENT__ 8 > // ARM:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // ARM:#define __CHAR16_TYPE__ unsigned short > // ARM:#define __CHAR32_TYPE__ unsigned int > @@ -1193,6 +1198,7 @@ > // ARM-BE-NOT:#define __ARMEL__ 1 > // ARM-BE:#define __ARM_ARCH_6J__ 1 > // ARM-BE:#define __ARM_BIG_ENDIAN 1 > +// ARM-BE:#define __BIGGEST_ALIGNMENT__ 8 > // ARM-BE:#define __BIG_ENDIAN__ 1 > // ARM-BE:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // ARM-BE:#define __CHAR16_TYPE__ unsigned short > @@ -1387,6 +1393,7 @@ > // ARMEABISOFTFP:#define __ARM_EABI__ 1 > // ARMEABISOFTFP:#define __ARM_PCS 1 > // ARMEABISOFTFP-NOT:#define __ARM_PCS_VFP 1 > +// ARMEABISOFTFP:#define __BIGGEST_ALIGNMENT__ 8 > // ARMEABISOFTFP:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // ARMEABISOFTFP:#define __CHAR16_TYPE__ unsigned short > // ARMEABISOFTFP:#define __CHAR32_TYPE__ unsigned int > @@ -1582,6 +1589,7 @@ > // ARMEABIHARDFP:#define __ARM_EABI__ 1 > // ARMEABIHARDFP:#define __ARM_PCS 1 > // ARMEABIHARDFP:#define __ARM_PCS_VFP 1 > +// ARMEABIHARDFP:#define __BIGGEST_ALIGNMENT__ 8 > // ARMEABIHARDFP:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // ARMEABIHARDFP:#define __CHAR16_TYPE__ unsigned short > // ARMEABIHARDFP:#define __CHAR32_TYPE__ unsigned int > @@ -1775,6 +1783,7 @@ > // ARM-NETBSD:#define __ARM_DWARF_EH__ 1 > // ARM-NETBSD:#define __ARM_EABI__ 1 > // ARM-NETBSD-NOT:#define __ARM_BIG_ENDIAN 1 > +// ARM-NETBSD:#define __BIGGEST_ALIGNMENT__ 8 > // ARM-NETBSD:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // ARM-NETBSD:#define __CHAR16_TYPE__ unsigned short > // ARM-NETBSD:#define __CHAR32_TYPE__ unsigned int > @@ -2021,6 +2030,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-none-none < > /dev/null | FileCheck -check-prefix I386 %s > // > // I386-NOT:#define _LP64 > +// I386:#define __BIGGEST_ALIGNMENT__ 16 > // I386:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // I386:#define __CHAR16_TYPE__ unsigned short > // I386:#define __CHAR32_TYPE__ unsigned int > @@ -2207,6 +2217,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-pc-linux-gnu > -target-cpu pentium4 < /dev/null | FileCheck -check-prefix I386-LINUX > %s > // > // I386-LINUX-NOT:#define _LP64 > +// I386-LINUX:#define __BIGGEST_ALIGNMENT__ 16 > // I386-LINUX:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // I386-LINUX:#define __CHAR16_TYPE__ unsigned short > // I386-LINUX:#define __CHAR32_TYPE__ unsigned int > @@ -2393,6 +2404,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-netbsd < > /dev/null | FileCheck -check-prefix I386-NETBSD %s > // > // I386-NETBSD-NOT:#define _LP64 > +// I386-NETBSD:#define __BIGGEST_ALIGNMENT__ 16 > // I386-NETBSD:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // I386-NETBSD:#define __CHAR16_TYPE__ unsigned short > // I386-NETBSD:#define __CHAR32_TYPE__ unsigned int > @@ -2597,6 +2609,7 @@ > // MIPS32BE:#define _MIPS_SZINT 32 > // MIPS32BE:#define _MIPS_SZLONG 32 > // MIPS32BE:#define _MIPS_SZPTR 32 > +// MIPS32BE:#define __BIGGEST_ALIGNMENT__ 8 > // MIPS32BE:#define __BIG_ENDIAN__ 1 > // MIPS32BE:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // MIPS32BE:#define __CHAR16_TYPE__ unsigned short > @@ -2805,6 +2818,7 @@ > // MIPS32EL:#define _MIPS_SZINT 32 > // MIPS32EL:#define _MIPS_SZLONG 32 > // MIPS32EL:#define _MIPS_SZPTR 32 > +// MIPS32EL:#define __BIGGEST_ALIGNMENT__ 8 > // MIPS32EL:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // MIPS32EL:#define __CHAR16_TYPE__ unsigned short > // MIPS32EL:#define __CHAR32_TYPE__ unsigned int > @@ -3010,6 +3024,7 @@ > // MIPS64BE:#define _MIPS_SZINT 32 > // MIPS64BE:#define _MIPS_SZLONG 64 > // MIPS64BE:#define _MIPS_SZPTR 64 > +// MIPS64BE:#define __BIGGEST_ALIGNMENT__ 16 > // MIPS64BE:#define __BIG_ENDIAN__ 1 > // MIPS64BE:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // MIPS64BE:#define __CHAR16_TYPE__ unsigned short > @@ -3218,6 +3233,7 @@ > // MIPS64EL:#define _MIPS_SZINT 32 > // MIPS64EL:#define _MIPS_SZLONG 64 > // MIPS64EL:#define _MIPS_SZPTR 64 > +// MIPS64EL:#define __BIGGEST_ALIGNMENT__ 16 > // MIPS64EL:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // MIPS64EL:#define __CHAR16_TYPE__ unsigned short > // MIPS64EL:#define __CHAR32_TYPE__ unsigned int > @@ -3583,6 +3599,7 @@ > // > // MSP430:#define MSP430 1 > // MSP430-NOT:#define _LP64 > +// MSP430:#define __BIGGEST_ALIGNMENT__ 2 > // MSP430:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // MSP430:#define __CHAR16_TYPE__ unsigned short > // MSP430:#define __CHAR32_TYPE__ unsigned int > @@ -3766,6 +3783,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=nvptx-none-none < > /dev/null | FileCheck -check-prefix NVPTX32 %s > // > // NVPTX32-NOT:#define _LP64 > +// NVPTX32:#define __BIGGEST_ALIGNMENT__ 8 > // NVPTX32:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // NVPTX32:#define __CHAR16_TYPE__ unsigned short > // NVPTX32:#define __CHAR32_TYPE__ unsigned int > @@ -3952,6 +3970,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=nvptx64-none-none < > /dev/null | FileCheck -check-prefix NVPTX64 %s > // > // NVPTX64:#define _LP64 1 > +// NVPTX64:#define __BIGGEST_ALIGNMENT__ 8 > // NVPTX64:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // NVPTX64:#define __CHAR16_TYPE__ unsigned short > // NVPTX64:#define __CHAR32_TYPE__ unsigned int > @@ -4143,6 +4162,7 @@ > // PPC603E:#define _ARCH_PPCGR 1 > // PPC603E:#define _BIG_ENDIAN 1 > // PPC603E-NOT:#define _LP64 > +// PPC603E:#define __BIGGEST_ALIGNMENT__ 8 > // PPC603E:#define __BIG_ENDIAN__ 1 > // PPC603E:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // PPC603E:#define __CHAR16_TYPE__ unsigned short > @@ -4340,6 +4360,7 @@ > // PPC64:#define _ARCH_PWR7 1 > // PPC64:#define _BIG_ENDIAN 1 > // PPC64:#define _LP64 1 > +// PPC64:#define __BIGGEST_ALIGNMENT__ 8 > // PPC64:#define __BIG_ENDIAN__ 1 > // PPC64:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // PPC64:#define __CHAR16_TYPE__ unsigned short > @@ -4542,6 +4563,7 @@ > // PPC64LE:#define _CALL_ELF 2 > // PPC64LE:#define _LITTLE_ENDIAN 1 > // PPC64LE:#define _LP64 1 > +// PPC64LE:#define __BIGGEST_ALIGNMENT__ 8 > // PPC64LE:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // PPC64LE:#define __CHAR16_TYPE__ unsigned short > // PPC64LE:#define __CHAR32_TYPE__ unsigned int > @@ -4923,6 +4945,7 @@ > // PPC64-LINUX:#define _ARCH_PPC64 1 > // PPC64-LINUX:#define _BIG_ENDIAN 1 > // PPC64-LINUX:#define _LP64 1 > +// PPC64-LINUX:#define __BIGGEST_ALIGNMENT__ 8 > // PPC64-LINUX:#define __BIG_ENDIAN__ 1 > // PPC64-LINUX:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // PPC64-LINUX:#define __CHAR16_TYPE__ unsigned short > @@ -5127,6 +5150,7 @@ > // PPC:#define _ARCH_PPC 1 > // PPC:#define _BIG_ENDIAN 1 > // PPC-NOT:#define _LP64 > +// PPC:#define __BIGGEST_ALIGNMENT__ 8 > // PPC:#define __BIG_ENDIAN__ 1 > // PPC:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // PPC:#define __CHAR16_TYPE__ unsigned short > @@ -5317,6 +5341,7 @@ > // PPC-LINUX:#define _ARCH_PPC 1 > // PPC-LINUX:#define _BIG_ENDIAN 1 > // PPC-LINUX-NOT:#define _LP64 > +// PPC-LINUX:#define __BIGGEST_ALIGNMENT__ 8 > // PPC-LINUX:#define __BIG_ENDIAN__ 1 > // PPC-LINUX:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // PPC-LINUX:#define __CHAR16_TYPE__ unsigned short > @@ -5508,6 +5533,7 @@ > // > // PPC-DARWIN:#define _ARCH_PPC 1 > // PPC-DARWIN:#define _BIG_ENDIAN 1 > +// PPC-DARWIN:#define __BIGGEST_ALIGNMENT__ 16 > // PPC-DARWIN:#define __BIG_ENDIAN__ 1 > // PPC-DARWIN:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // PPC-DARWIN:#define __CHAR16_TYPE__ unsigned short > @@ -5701,6 +5727,7 @@ > // > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=s390x-none-none > -fno-signed-char < /dev/null | FileCheck -check-prefix S390X %s > // > +// S390X:#define __BIGGEST_ALIGNMENT__ 8 > // S390X:#define __CHAR16_TYPE__ unsigned short > // S390X:#define __CHAR32_TYPE__ unsigned int > // S390X:#define __CHAR_BIT__ 8 > @@ -5882,6 +5909,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=sparc-none-none < > /dev/null | FileCheck -check-prefix SPARC %s > // > // SPARC-NOT:#define _LP64 > +// SPARC:#define __BIGGEST_ALIGNMENT__ 8 > // SPARC:#define __BIG_ENDIAN__ 1 > // SPARC:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // SPARC:#define __CHAR16_TYPE__ unsigned short > @@ -6069,6 +6097,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=tce-none-none < > /dev/null | FileCheck -check-prefix TCE %s > // > // TCE-NOT:#define _LP64 > +// TCE:#define __BIGGEST_ALIGNMENT__ 4 > // TCE:#define __BIG_ENDIAN__ 1 > // TCE:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__ > // TCE:#define __CHAR16_TYPE__ unsigned short > @@ -6236,6 +6265,7 @@ > // > // X86_64:#define _LP64 1 > // X86_64-NOT:#define _LP32 1 > +// X86_64:#define __BIGGEST_ALIGNMENT__ 16 > // X86_64:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // X86_64:#define __CHAR16_TYPE__ unsigned short > // X86_64:#define __CHAR32_TYPE__ unsigned int > @@ -6437,6 +6467,7 @@ > // > // X32:#define _ILP32 1 > // X32-NOT:#define _LP64 1 > +// X32:#define __BIGGEST_ALIGNMENT__ 16 > // X32:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // X32:#define __CHAR16_TYPE__ unsigned short > // X32:#define __CHAR32_TYPE__ unsigned int > @@ -6630,6 +6661,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-pc-linux-gnu > < /dev/null | FileCheck -check-prefix X86_64-LINUX %s > // > // X86_64-LINUX:#define _LP64 1 > +// X86_64-LINUX:#define __BIGGEST_ALIGNMENT__ 16 > // X86_64-LINUX:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // X86_64-LINUX:#define __CHAR16_TYPE__ unsigned short > // X86_64-LINUX:#define __CHAR32_TYPE__ unsigned int > @@ -6828,6 +6860,7 @@ > // RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-netbsd < > /dev/null | FileCheck -check-prefix X86_64-NETBSD %s > // > // X86_64-NETBSD:#define _LP64 1 > +// X86_64-NETBSD:#define __BIGGEST_ALIGNMENT__ 16 > // X86_64-NETBSD:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ > // X86_64-NETBSD:#define __CHAR16_TYPE__ unsigned short > // X86_64-NETBSD:#define __CHAR32_TYPE__ unsigned int > -- > 1.7.7.6 > _______________________________________________ > cfe-commits mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits >
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