[RecordLayout] Don't align to non-power-of-2 sizes when using -mms-bitfields
When targeting GNU/MinGW for i386, the size of the "long double" data type is 12 bytes (while it is 8 bytes in MSVC). When building with -mms-bitfields to have struct layouts match MSVC, data types are laid out in a struct with alignment according to their size. However, this doesn't make sense for the long double type, since it doesn't match MSVC at all, and aligning to a non-power-of-2 size triggers other asserts later. This matches what GCC does, aligning a long double to 4 bytes in structs on i386 even when -mms-bitfields is specified. This fixes asserts when using the max_align_t data type when building for MinGW/i386 with the -mms-bitfields flag. Differential Revision: https://reviews.llvm.org/D43734 llvm-svn: 326173
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@ -1752,7 +1752,12 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
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QualType T = Context.getBaseElementType(D->getType());
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if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
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CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
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if (TypeSize > FieldAlign)
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assert(
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(llvm::isPowerOf2_64(TypeSize.getQuantity()) ||
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Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) &&
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"Non PowerOf2 size outside of GNU mode");
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if (TypeSize > FieldAlign &&
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llvm::isPowerOf2_64(TypeSize.getQuantity()))
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FieldAlign = TypeSize;
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}
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}
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@ -1,5 +1,7 @@
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// RUN: %clang_cc1 -triple i686-windows-gnu -emit-llvm -o - %s \
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// RUN: | FileCheck %s --check-prefix=GNU32
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// RUN: %clang_cc1 -triple i686-windows-gnu -emit-llvm -o - %s -mms-bitfields \
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// RUN: | FileCheck %s --check-prefix=GNU32
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// RUN: %clang_cc1 -triple x86_64-windows-gnu -emit-llvm -o - %s \
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// RUN: | FileCheck %s --check-prefix=GNU64
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// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -o - %s \
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