[llvm-commits] [llvm] r139651 - in /llvm/trunk/lib/CodeGen: SplitKit.cpp SplitKit.h
Jakob Stoklund Olesen
stoklund at 2pi.dk
Tue Sep 13 15:22:39 PDT 2011
Author: stoklund
Date: Tue Sep 13 17:22:39 2011
New Revision: 139651
URL: http://llvm.org/viewvc/llvm-project?rev=139651&view=rev
Log:
Implement -split-spill-mode=size.
Whenever the complement interval is defined by multiple copies of the
same value, hoist those back-copies to the nearest common dominator.
This ensures that at most one copy is inserted per value in the
complement inteval, and no phi-defs are needed.
Modified:
llvm/trunk/lib/CodeGen/SplitKit.cpp
llvm/trunk/lib/CodeGen/SplitKit.h
Modified: llvm/trunk/lib/CodeGen/SplitKit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SplitKit.cpp?rev=139651&r1=139650&r2=139651&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.cpp (original)
+++ llvm/trunk/lib/CodeGen/SplitKit.cpp Tue Sep 13 17:22:39 2011
@@ -592,6 +592,149 @@
DEBUG(dump());
}
+//===----------------------------------------------------------------------===//
+// Spill modes
+//===----------------------------------------------------------------------===//
+
+void SplitEditor::removeBackCopies(SmallVectorImpl<VNInfo*> &Copies) {
+ LiveInterval *LI = Edit->get(0);
+ DEBUG(dbgs() << "Removing " << Copies.size() << " back-copies.\n");
+ RegAssignMap::iterator AssignI;
+ AssignI.setMap(RegAssign);
+
+ for (unsigned i = 0, e = Copies.size(); i != e; ++i) {
+ VNInfo *VNI = Copies[i];
+ SlotIndex Def = VNI->def;
+ MachineInstr *MI = LIS.getInstructionFromIndex(Def);
+ assert(MI && "No instruction for back-copy");
+
+ MachineBasicBlock *MBB = MI->getParent();
+ MachineBasicBlock::iterator MBBI(MI);
+ bool AtBegin;
+ do AtBegin = MBBI == MBB->begin();
+ while (!AtBegin && (--MBBI)->isDebugValue());
+
+ DEBUG(dbgs() << "Removing " << Def << '\t' << *MI);
+ LI->removeValNo(VNI);
+ LIS.RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+
+ // Adjust RegAssign if a register assignment is killed at VNI->def. We
+ // want to avoid calculating the live range of the source register if
+ // possible.
+ AssignI.find(VNI->def.getPrevSlot());
+ if (!AssignI.valid() || AssignI.start() >= Def)
+ continue;
+ // If MI doesn't kill the assigned register, just leave it.
+ if (AssignI.stop() != Def)
+ continue;
+ unsigned RegIdx = AssignI.value();
+ if (AtBegin || !MBBI->readsVirtualRegister(Edit->getReg())) {
+ DEBUG(dbgs() << " cannot find simple kill of RegIdx " << RegIdx << '\n');
+ markComplexMapped(RegIdx, Edit->getParent().getVNInfoAt(Def));
+ } else {
+ SlotIndex Kill = LIS.getInstructionIndex(MBBI).getDefIndex();
+ DEBUG(dbgs() << " move kill to " << Kill << '\t' << *MBBI);
+ AssignI.setStop(Kill);
+ }
+ }
+}
+
+void SplitEditor::hoistCopiesForSize() {
+ // Get the complement interval, always RegIdx 0.
+ LiveInterval *LI = Edit->get(0);
+ LiveInterval *Parent = &Edit->getParent();
+
+ // Track the nearest common dominator for all back-copies for each ParentVNI,
+ // indexed by ParentVNI->id.
+ typedef std::pair<MachineBasicBlock*, SlotIndex> DomPair;
+ SmallVector<DomPair, 8> NearestDom(Parent->getNumValNums());
+
+ // Find the nearest common dominator for parent values with multiple
+ // back-copies. If a single back-copy dominates, put it in DomPair.second.
+ for (LiveInterval::vni_iterator VI = LI->vni_begin(), VE = LI->vni_end();
+ VI != VE; ++VI) {
+ VNInfo *VNI = *VI;
+ VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(VNI->def);
+ assert(ParentVNI && "Parent not live at complement def");
+
+ // Don't hoist remats. The complement is probably going to disappear
+ // completely anyway.
+ if (Edit->didRematerialize(ParentVNI))
+ continue;
+
+ MachineBasicBlock *ValMBB = LIS.getMBBFromIndex(VNI->def);
+ DomPair &Dom = NearestDom[ParentVNI->id];
+
+ // Keep directly defined parent values. This is either a PHI or an
+ // instruction in the complement range. All other copies of ParentVNI
+ // should be eliminated.
+ if (VNI->def == ParentVNI->def) {
+ DEBUG(dbgs() << "Direct complement def at " << VNI->def << '\n');
+ Dom = DomPair(ValMBB, VNI->def);
+ continue;
+ }
+ // Skip the singly mapped values. There is nothing to gain from hoisting a
+ // single back-copy.
+ if (Values.lookup(std::make_pair(0, ParentVNI->id))) {
+ DEBUG(dbgs() << "Single complement def at " << VNI->def << '\n');
+ continue;
+ }
+
+ if (!Dom.first) {
+ // First time we see ParentVNI. VNI dominates itself.
+ Dom = DomPair(ValMBB, VNI->def);
+ } else if (Dom.first == ValMBB) {
+ // Two defs in the same block. Pick the earlier def.
+ if (!Dom.second.isValid() || VNI->def < Dom.second)
+ Dom.second = VNI->def;
+ } else {
+ // Different basic blocks. Check if one dominates.
+ MachineBasicBlock *Near =
+ MDT.findNearestCommonDominator(Dom.first, ValMBB);
+ if (Near == ValMBB)
+ // Def ValMBB dominates.
+ Dom = DomPair(ValMBB, VNI->def);
+ else if (Near != Dom.first)
+ // None dominate. Hoist to common dominator, need new def.
+ Dom = DomPair(Near, SlotIndex());
+ }
+
+ DEBUG(dbgs() << "Multi-mapped complement " << VNI->id << '@' << VNI->def
+ << " for parent " << ParentVNI->id << '@' << ParentVNI->def
+ << " hoist to BB#" << Dom.first->getNumber() << ' '
+ << Dom.second << '\n');
+ }
+
+ // Insert the hoisted copies.
+ for (unsigned i = 0, e = Parent->getNumValNums(); i != e; ++i) {
+ DomPair &Dom = NearestDom[i];
+ if (!Dom.first || Dom.second.isValid())
+ continue;
+ // This value needs a hoisted copy inserted at the end of Dom.second.
+ SlotIndex Last = LIS.getMBBEndIdx(Dom.first).getPrevSlot();
+ Dom.second =
+ defFromParent(0, Parent->getValNumInfo(i), Last, *Dom.first,
+ LIS.getLastSplitPoint(Edit->getParent(), Dom.first))->def;
+ }
+
+ // Remove redundant back-copies that are now known to be dominated by another
+ // def with the same value.
+ SmallVector<VNInfo*, 8> BackCopies;
+ for (LiveInterval::vni_iterator VI = LI->vni_begin(), VE = LI->vni_end();
+ VI != VE; ++VI) {
+ VNInfo *VNI = *VI;
+ VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(VNI->def);
+ const DomPair &Dom = NearestDom[ParentVNI->id];
+ if (!Dom.first || Dom.second == VNI->def)
+ continue;
+ BackCopies.push_back(VNI);
+ markOverlappedComplement(ParentVNI);
+ }
+ removeBackCopies(BackCopies);
+}
+
+
/// transferValues - Transfer all possible values to the new live ranges.
/// Values that were rematerialized are left alone, they need LRCalc.extend().
bool SplitEditor::transferValues() {
@@ -831,6 +974,19 @@
markComplexMapped(i, ParentVNI);
}
+ // Hoist back-copies to the complement interval when in spill mode.
+ switch (SpillMode) {
+ case SM_Partition:
+ // Leave all back-copies as is.
+ break;
+ case SM_Size:
+ hoistCopiesForSize();
+ break;
+ case SM_Speed:
+ llvm_unreachable("Spill mode 'speed' not implemented yet");
+ break;
+ }
+
// Transfer the simply mapped values, check if any are skipped.
bool Skipped = transferValues();
if (Skipped)
Modified: llvm/trunk/lib/CodeGen/SplitKit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SplitKit.h?rev=139651&r1=139650&r2=139651&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.h (original)
+++ llvm/trunk/lib/CodeGen/SplitKit.h Tue Sep 13 17:22:39 2011
@@ -319,6 +319,14 @@
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I);
+ /// removeBackCopies - Remove the copy instructions that defines the values
+ /// in the vector in the complement interval.
+ void removeBackCopies(SmallVectorImpl<VNInfo*> &Copies);
+
+ /// hoistCopiesForSize - Hoist back-copies to the complement interval in a
+ /// way that minimizes code size. This implements the SM_Size spill mode.
+ void hoistCopiesForSize();
+
/// transferValues - Transfer values to the new ranges.
/// Return true if any ranges were skipped.
bool transferValues();
More information about the llvm-commits
mailing list