Commit ba3c53d0 authored by Tom Stellard's avatar Tom Stellard
Browse files

Merging r326173: 

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r326173 | mstorsjo | 2018-02-26 22:27:06 -0800 (Mon, 26 Feb 2018) | 17 lines

[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
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llvm-svn: 333569
parent e15bb83e

clang/lib/AST/RecordLayoutBuilder.cpp

+6 −1
Original line number Diff line number Diff line
@@ -1751,7 +1751,12 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, 
      QualType T = Context.getBaseElementType(D->getType());

      if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {

        CharUnits TypeSize = Context.getTypeSizeInChars(BTy);

        if (TypeSize > FieldAlign)

        assert(

            (llvm::isPowerOf2_64(TypeSize.getQuantity()) ||

             Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) &&

            "Non PowerOf2 size outside of GNU mode");

        if (TypeSize > FieldAlign &&

            llvm::isPowerOf2_64(TypeSize.getQuantity()))

          FieldAlign = TypeSize;

      }

    }

clang/test/CodeGen/mingw-long-double.c

+2 −0
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -triple i686-windows-gnu -emit-llvm -o - %s \

// RUN:    | FileCheck %s --check-prefix=GNU32

// RUN: %clang_cc1 -triple i686-windows-gnu -emit-llvm -o - %s -mms-bitfields \

// RUN:    | FileCheck %s --check-prefix=GNU32

// RUN: %clang_cc1 -triple x86_64-windows-gnu -emit-llvm -o - %s \

// RUN:    | FileCheck %s --check-prefix=GNU64

// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -o - %s \