[llvm-commits] [llvm] r127287 - in /llvm/trunk/lib/CodeGen: LiveRangeEdit.cpp LiveRangeEdit.h SplitKit.cpp SplitKit.h
Jakob Stoklund Olesen
stoklund at 2pi.dk
Tue Mar 8 14:46:11 PST 2011
Author: stoklund
Date: Tue Mar 8 16:46:11 2011
New Revision: 127287
URL: http://llvm.org/viewvc/llvm-project?rev=127287&view=rev
Log:
Delete dead code after rematerializing.
LiveRangeEdit::eliminateDeadDefs() will eventually be used by coalescing,
splitting, and spilling for dead code elimination. It can delete chains of dead
instructions as long as there are no dependency loops.
Modified:
llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
llvm/trunk/lib/CodeGen/LiveRangeEdit.h
llvm/trunk/lib/CodeGen/SplitKit.cpp
llvm/trunk/lib/CodeGen/SplitKit.h
Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp?rev=127287&r1=127286&r2=127287&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp Tue Mar 8 16:46:11 2011
@@ -13,9 +13,12 @@
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
@@ -128,3 +131,59 @@
return lis.InsertMachineInstrInMaps(--MI).getDefIndex();
}
+void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
+ LiveIntervals &LIS,
+ const TargetInstrInfo &TII) {
+ SetVector<LiveInterval*,
+ SmallVector<LiveInterval*, 8>,
+ SmallPtrSet<LiveInterval*, 8> > ToShrink;
+
+ for (;;) {
+ // Erase all dead defs.
+ while (!Dead.empty()) {
+ MachineInstr *MI = Dead.pop_back_val();
+ assert(MI->allDefsAreDead() && "Def isn't really dead");
+
+ // Never delete inline asm.
+ if (MI->isInlineAsm())
+ continue;
+
+ // Use the same criteria as DeadMachineInstructionElim.
+ bool SawStore = false;
+ if (!MI->isSafeToMove(&TII, 0, SawStore))
+ continue;
+
+ SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
+ DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
+
+ // Check for live intervals that may shrink
+ for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
+ MOE = MI->operands_end(); MOI != MOE; ++MOI) {
+ if (!MOI->isReg())
+ continue;
+ unsigned Reg = MOI->getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg))
+ continue;
+ LiveInterval &LI = LIS.getInterval(Reg);
+ // Remove defined value.
+ if (MOI->isDef())
+ if (VNInfo *VNI = LI.getVNInfoAt(Idx))
+ LI.removeValNo(VNI);
+ // Shrink read registers.
+ if (MI->readsVirtualRegister(Reg))
+ ToShrink.insert(&LI);
+ }
+
+ LIS.RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+ }
+
+ if (ToShrink.empty())
+ break;
+
+ // Shrink just one live interval. Then delete new dead defs.
+ LIS.shrinkToUses(ToShrink.back(), &Dead);
+ ToShrink.pop_back();
+ }
+}
+
Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.h?rev=127287&r1=127286&r2=127287&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.h (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.h Tue Mar 8 16:46:11 2011
@@ -128,6 +128,14 @@
bool didRematerialize(const VNInfo *ParentVNI) const {
return rematted_.count(ParentVNI);
}
+
+ /// eliminateDeadDefs - Try to delete machine instructions that are now dead
+ /// (allDefsAreDead returns true). This may cause live intervals to be trimmed
+ /// and further dead efs to be eliminated.
+ void eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
+ LiveIntervals&,
+ const TargetInstrInfo&);
+
};
}
Modified: llvm/trunk/lib/CodeGen/SplitKit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SplitKit.cpp?rev=127287&r1=127286&r2=127287&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.cpp (original)
+++ llvm/trunk/lib/CodeGen/SplitKit.cpp Tue Mar 8 16:46:11 2011
@@ -797,6 +797,40 @@
}
}
+void SplitEditor::deleteRematVictims() {
+ SmallVector<MachineInstr*, 8> Dead;
+ for (LiveInterval::const_vni_iterator I = Edit->getParent().vni_begin(),
+ E = Edit->getParent().vni_end(); I != E; ++I) {
+ const VNInfo *VNI = *I;
+ // Was VNI rematted anywhere?
+ if (VNI->isUnused() || VNI->isPHIDef() || !Edit->didRematerialize(VNI))
+ continue;
+ unsigned RegIdx = RegAssign.lookup(VNI->def);
+ LiveInterval *LI = Edit->get(RegIdx);
+ LiveInterval::const_iterator LII = LI->FindLiveRangeContaining(VNI->def);
+ assert(LII != LI->end() && "Missing live range for rematted def");
+
+ // Is this a dead def?
+ if (LII->end != VNI->def.getNextSlot())
+ continue;
+
+ MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
+ assert(MI && "Missing instruction for dead def");
+ MI->addRegisterDead(LI->reg, &TRI);
+
+ if (!MI->allDefsAreDead())
+ continue;
+
+ DEBUG(dbgs() << "All defs dead: " << *MI);
+ Dead.push_back(MI);
+ }
+
+ if (Dead.empty())
+ return;
+
+ Edit->eliminateDeadDefs(Dead, LIS, TII);
+}
+
void SplitEditor::finish() {
assert(OpenIdx == 0 && "Previous LI not closed before rewrite");
++NumFinished;
@@ -835,7 +869,9 @@
// Rewrite virtual registers, possibly extending ranges.
rewriteAssigned(Complex);
- // FIXME: Delete defs that were rematted everywhere.
+ // Delete defs that were rematted everywhere.
+ if (Complex)
+ deleteRematVictims();
// Get rid of unused values and set phi-kill flags.
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I)
Modified: llvm/trunk/lib/CodeGen/SplitKit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SplitKit.h?rev=127287&r1=127286&r2=127287&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.h (original)
+++ llvm/trunk/lib/CodeGen/SplitKit.h Tue Mar 8 16:46:11 2011
@@ -272,6 +272,9 @@
void rewriteComponents(const SmallVectorImpl<LiveInterval*> &Intvs,
const ConnectedVNInfoEqClasses &ConEq);
+ /// deleteRematVictims - Delete defs that are dead after rematerializing.
+ void deleteRematVictims();
+
public:
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
/// Newly created intervals will be appended to newIntervals.
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