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COFF: Don't oversize COMMON symbols when targeting BFD ld

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COFF normally doesn't allow us to describe the alignment of COMMON
symbols.

It turns out that most linkers use the symbol size as a hint as to how
aligned the symbol should be.

However the BFD folks have added a .drectve command, which we
now support as of r219229, that allows us to specify the alignment
precisely.  With this in mind, stop rounding sizes up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219281 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-10-08 06:38:53 +00:00
parent 3d371bd84b
commit 1fa70c99dc
2 changed files with 12 additions and 6 deletions
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9
lib/MC/WinCOFFStreamer.cpp
View File

@ -185,14 +185,13 @@ void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
"Got non-COFF section in the COFF backend!");
const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
if (T.isKnownWindowsMSVCEnvironment())
if (T.isKnownWindowsMSVCEnvironment()) {
if (ByteAlignment > 32)
report_fatal_error("alignment is limited to 32-bytes");
// Round size up to alignment so that we will honor the alignment request.
// TODO: We don't need to do this if we are targeting the bfd linker once we
// add support for adding -aligncomm into the .drectve section.
Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
// Round size up to alignment so that we will honor the alignment request.
Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
}
AssignSection(Symbol, nullptr);

9
test/MC/COFF/comm-align.s
View File

@ -24,6 +24,8 @@ _a:
.comm _s_4,4,2 # @s_3
.comm _s_8,4,3 # @s_4
.comm _small_but_overaligned,1,3 # @s_4
.text
.def _b
@ -41,10 +43,15 @@ _b:
# CHECK: Section: .text (1)
# CHECK: }
# CHECK: Symbol {
# CHECK: Name: _small_but_overaligned
# CHECK-NEXT:Value: 1
# CHECK-NEXT:Section: IMAGE_SYM_UNDEFINED (0)
# CHECK: }
# CHECK: Symbol {
# CHECK: Name: _b
# CHECK: Section: .text (1)
# CHECK: }
# CHECK: ]
# CHECK: Directive(s): -aligncomm:"_s_2",1 -aligncomm:"_s_4",2 -aligncomm:"_s_8",3
# CHECK: Directive(s): -aligncomm:"_s_2",1 -aligncomm:"_s_4",2 -aligncomm:"_s_8",3 -aligncomm:"_small_but_overaligned",3