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David Majnemer 31b080d57f MC: Support aligned COMMON symbols for COFF

link.exe:
Fuzz testing has shown that COMMON symbols with size > 32 will always
have an alignment of at least 32 and all symbols with size < 32 will
have an alignment of at least the largest power of 2 less than the size
of the symbol.

binutils:
The BFD linker essentially work like the link.exe behavior but with
alignment 4 instead of 32.  The BFD linker also supports an extension to
COFF which adds an -aligncomm argument to the .drectve section which
permits specifying a precise alignment for a variable but MC currently
doesn't support editing .drectve in this way.

With all of this in mind, we decide to play a little trick: we can
ensure that the alignment will be respected by bumping the size of the
global to it's alignment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218201 91177308-0d34-0410-b5e6-96231b3b80d8

2014-09-21 09:18:07 +00:00

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 ; RUN: llc -mtriple i386-pc-mingw32 < %s | FileCheck %s
 @a = internal global i8 0, align 1
 @b = internal global double 0.000000e+00, align 8
 @c = common global i8 0, align 1
 @d = common global double 0.000000e+00, align 8
 ; .lcomm uses byte alignment
 ; CHECK: .lcomm	_a,1
 ; CHECK: .lcomm	_b,8,8
 ; .comm uses log2 alignment
 ; CHECK: .comm	_c,1,0
 ; CHECK: .comm	_d,8,3