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MC: Switch to using explicit MCAlignFragments with OnlyAlignAddress bit instead

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of manually doing padding/editing layout in LayoutSection().
    - This probably seems like six-of-one and half-dozen of another, but there
      is a method to my madness.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103693 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Dunbar 2010-05-13 02:34:14 +00:00
parent 69b9f9883e
commit 61066dbdf2
1 changed files with 31 additions and 22 deletions
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53
lib/MC/MCAssembler.cpp
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@ -442,7 +442,7 @@ void MCAssembler::LayoutSection(MCAsmLayout &Layout,
++stats::SectionLayouts;
// Get the section start address.
// Compute the section start address.
uint64_t StartAddress = 0;
if (SectionOrderIndex) {
MCSectionData *Prev = Layout.getSectionOrder()[SectionOrderIndex - 1];
@ -450,22 +450,10 @@ void MCAssembler::LayoutSection(MCAsmLayout &Layout,
Layout.getSectionAddressSize(Prev));
}
// Align this section if necessary by adding padding bytes to the previous
// section. It is safe to adjust this out-of-band, because no symbol or
// fragment is allowed to point past the end of the section at any time.
if (uint64_t Pad = OffsetToAlignment(StartAddress, SD.getAlignment())) {
// Unless this section is virtual (where we are allowed to adjust the offset
// freely), the padding goes in the previous section.
if (!IsVirtual) {
assert(SectionOrderIndex && "Invalid initial section address!");
MCSectionData *Prev = Layout.getSectionOrder()[SectionOrderIndex - 1];
Layout.setSectionFileSize(Prev, Layout.getSectionFileSize(Prev) + Pad);
}
// Honor the section alignment requirements.
StartAddress = RoundUpToAlignment(StartAddress, SD.getAlignment());
StartAddress += Pad;
}
// Set the aligned section address.
// Set the section address.
Layout.setSectionAddress(&SD, StartAddress);
for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it)
@ -587,7 +575,6 @@ static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
void MCAssembler::WriteSectionData(const MCSectionData *SD,
const MCAsmLayout &Layout,
MCObjectWriter *OW) const {
uint64_t SectionSize = Layout.getSectionSize(SD);
uint64_t SectionFileSize = Layout.getSectionFileSize(SD);
// Ignore virtual sections.
@ -621,10 +608,6 @@ void MCAssembler::WriteSectionData(const MCSectionData *SD,
ie = SD->end(); it != ie; ++it)
WriteFragmentData(*this, Layout, *it, OW);
// Add section padding.
assert(SectionFileSize >= SectionSize && "Invalid section sizes!");
OW->WriteZeros(SectionFileSize - SectionSize);
assert(OW->getStream().tell() - Start == SectionFileSize);
}
@ -645,8 +628,34 @@ void MCAssembler::Finish() {
it2->setOrdinal(FragmentIndex++);
}
// Layout until everything fits.
// Create the layout object.
MCAsmLayout Layout(*this);
// Insert additional align fragments for concrete sections to explicitly pad
// the previous section to match their alignment requirements. This is for
// 'gas' compatibility, it shouldn't strictly be necessary.
//
// FIXME: This may be Mach-O specific.
for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
MCSectionData *SD = Layout.getSectionOrder()[i];
// Ignore sections without alignment requirements.
unsigned Align = SD->getAlignment();
if (Align <= 1)
continue;
// Ignore virtual sections, they don't cause file size modifications.
if (getBackend().isVirtualSection(SD->getSection()))
continue;
// Otherwise, create a new align fragment at the end of the previous
// section.
MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
Layout.getSectionOrder()[i - 1]);
AF->setOnlyAlignAddress(true);
}
// Layout until everything fits.
while (LayoutOnce(Layout))
continue;