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MC: Switch to completely lazy layout.

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- The eliminates the last major algorithmic problem with MC.

llvm-svn: 103754
This commit is contained in:
Daniel Dunbar 2010-05-14 00:51:14 +00:00
parent 66c2ccec2d
commit 7fee3c7b28
2 changed files with 39 additions and 19 deletions
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4
include/llvm/MC/MCAsmLayout.h
View File

@ -41,6 +41,10 @@ private:
/// lower ordinal will be up to date.
mutable MCFragment *LastValidFragment;
/// \brief Make sure that the layout for the given fragment is valid, lazily
/// computing it if necessary.
void EnsureValid(const MCFragment *F) const;
bool isSectionUpToDate(const MCSectionData *SD) const;
bool isFragmentUpToDate(const MCFragment *F) const;

54
lib/MC/MCAssembler.cpp
View File

@ -77,18 +77,38 @@ bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const {
}
void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
// We shouldn't have to do anything special to support negative slides, and it
// is a perfectly valid thing to do as long as other parts of the system can
// guarantee convergence.
assert(SlideAmount >= 0 && "Negative slides not yet supported");
// If this fragment wasn't already up-to-date, we don't need to do anything.
if (!isFragmentUpToDate(F))
return;
// Update the layout by simply recomputing the layout for the entire
// file. This is trivially correct, but very slow.
//
// FIXME-PERF: This is O(N^2), but will be eliminated once we get smarter.
// Otherwise, reset the last valid fragment to the predecessor of the
// invalidated fragment.
LastValidFragment = F->getPrevNode();
if (!LastValidFragment) {
unsigned Index = F->getParent()->getLayoutOrder();
if (Index != 0) {
MCSectionData *Prev = getSectionOrder()[Index - 1];
LastValidFragment = &(Prev->getFragmentList().back());
}
}
}
// Layout the sections in order.
LayoutFile();
void MCAsmLayout::EnsureValid(const MCFragment *F) const {
// Advance the layout position until the fragment is up-to-date.
while (!isFragmentUpToDate(F)) {
// Advance to the next fragment.
MCFragment *Cur = LastValidFragment;
if (Cur)
Cur = Cur->getNextNode();
if (!Cur) {
unsigned NextIndex = 0;
if (LastValidFragment)
NextIndex = LastValidFragment->getParent()->getLayoutOrder() + 1;
Cur = SectionOrder[NextIndex]->begin();
}
const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur);
}
}
void MCAsmLayout::FragmentReplaced(MCFragment *Src, MCFragment *Dst) {
@ -105,11 +125,13 @@ uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
}
uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
EnsureValid(F);
assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
return F->EffectiveSize;
}
uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
EnsureValid(F);
assert(F->Offset != ~UINT64_C(0) && "Address not set!");
return F->Offset;
}
@ -120,6 +142,7 @@ uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
}
uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
EnsureValid(SD->begin());
assert(SD->Address != ~UINT64_C(0) && "Address not set!");
return SD->Address;
}
@ -436,18 +459,11 @@ uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
}
void MCAsmLayout::LayoutFile() {
// Initialize the first section and set the valid fragment layout point.
// Initialize the first section and set the valid fragment layout point. All
// actual layout computations are done lazily.
LastValidFragment = 0;
if (!getSectionOrder().empty())
getSectionOrder().front()->Address = 0;
for (unsigned i = 0, e = getSectionOrder().size(); i != e; ++i) {
MCSectionData *SD = getSectionOrder()[i];
for (MCSectionData::iterator it = SD->begin(),
ie = SD->end(); it != ie; ++it)
LayoutFragment(it);
}
}
void MCAsmLayout::LayoutFragment(MCFragment *F) {