Commit Graph

4 Commits

Author SHA1 Message Date
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
David Majnemer
c7210b3f0b llvm-readobj: pretty-print special COFF section names
Print IMAGE_SYM_DEBUG and the like instead of (-2).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218172 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-20 00:25:06 +00:00
David Majnemer
e4d89ec8de WinCOFF: Emit common symbols as specified in the COFF spec
Summary:
Local common symbols were properly inserted into the .bss section.
However, putting external common symbols in the .bss section would give
them a strong definition.

Instead, encode them as undefined, external symbols who's symbol value
is equivalent to their size.

Reviewers: Bigcheese, rafael, rnk

CC: llvm-commits

Differential Revision: http://reviews.llvm.org/D3324

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205811 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-08 22:33:40 +00:00
Rafael Espindola
c7daeb3098 Fix .comm and .lcomm on COFF.
These should not use COMDATs. GNU as uses .bss for .lcomm and section 0 for
.comm.

Given

static int a;
int b;

MSVC puts both in .bss. This patch then puts both .comm and .lcomm on .bss. With
this change we agree with gas on .lcomm, are much closer on .comm and clang-cl
matches msvc on the above example.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195654 91177308-0d34-0410-b5e6-96231b3b80d8
2013-11-25 16:06:04 +00:00