[llvm-commits] [llvm] r103754 - in /llvm/trunk: include/llvm/MC/MCAsmLayout.h lib/MC/MCAssembler.cpp

[Daniel Dunbar]

Author: ddunbar
Date: Thu May 13 19:51:14 2010
New Revision: 103754

URL: http://llvm.org/viewvc/llvm-project?rev=103754&view=rev
Log:
MC: Switch to completely lazy layout.
 - The eliminates the last major algorithmic problem with MC.

Modified:
    llvm/trunk/include/llvm/MC/MCAsmLayout.h
    llvm/trunk/lib/MC/MCAssembler.cpp

Modified: llvm/trunk/include/llvm/MC/MCAsmLayout.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCAsmLayout.h?rev=103754&r1=103753&r2=103754&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCAsmLayout.h (original)
+++ llvm/trunk/include/llvm/MC/MCAsmLayout.h Thu May 13 19:51:14 2010
@@ -41,6 +41,10 @@
   /// 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;
 

Modified: llvm/trunk/lib/MC/MCAssembler.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCAssembler.cpp?rev=103754&r1=103753&r2=103754&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCAssembler.cpp (original)
+++ llvm/trunk/lib/MC/MCAssembler.cpp Thu May 13 19:51:14 2010
@@ -77,18 +77,38 @@
 }
 
 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::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::getSectionAddress(const MCSectionData *SD) const {
+  EnsureValid(SD->begin());
   assert(SD->Address != ~UINT64_C(0) && "Address not set!");
   return SD->Address;
 }
@@ -436,18 +459,11 @@
 }
 
 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) {