[llvm] r184571 - Refactor LiveRangeEdit::eliminateDeadDefs.
Andrew Trick
atrick at apple.com
Fri Jun 21 11:33:17 PDT 2013
Author: atrick
Date: Fri Jun 21 13:33:17 2013
New Revision: 184571
URL: http://llvm.org/viewvc/llvm-project?rev=184571&view=rev
Log:
Refactor LiveRangeEdit::eliminateDeadDefs.
I want to add logic to handle more cases.
Modified:
llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h
llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
Modified: llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h?rev=184571&r1=184570&r2=184571&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h (original)
+++ llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h Fri Jun 21 13:33:17 2013
@@ -19,6 +19,7 @@
#define LLVM_CODEGEN_LIVERANGEEDIT_H
#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/Target/TargetMachine.h"
@@ -90,6 +91,12 @@ private:
/// a load, eliminate the register by folding the def into the use.
bool foldAsLoad(LiveInterval *LI, SmallVectorImpl<MachineInstr*> &Dead);
+ typedef SetVector<LiveInterval*,
+ SmallVector<LiveInterval*, 8>,
+ SmallPtrSet<LiveInterval*, 8> > ToShrinkSet;
+ /// Helper for eliminateDeadDefs.
+ void eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink);
+
public:
/// Create a LiveRangeEdit for breaking down parent into smaller pieces.
/// @param parent The register being spilled or split.
Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp?rev=184571&r1=184570&r2=184571&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp Fri Jun 21 13:33:17 2013
@@ -13,7 +13,6 @@
#define DEBUG_TYPE "regalloc"
#include "llvm/CodeGen/LiveRangeEdit.h"
-#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
@@ -216,108 +215,109 @@ bool LiveRangeEdit::foldAsLoad(LiveInter
return true;
}
-void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
- ArrayRef<unsigned> RegsBeingSpilled) {
- 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");
- SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
-
- // Never delete inline asm.
- if (MI->isInlineAsm()) {
- DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
- continue;
- }
+/// Find all live intervals that need to shrink, then remove the instruction.
+void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
+ assert(MI->allDefsAreDead() && "Def isn't really dead");
+ SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
+
+ // Never delete inline asm.
+ if (MI->isInlineAsm()) {
+ DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
+ return;
+ }
- // Use the same criteria as DeadMachineInstructionElim.
- bool SawStore = false;
- if (!MI->isSafeToMove(&TII, 0, SawStore)) {
- DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
- continue;
- }
+ // Use the same criteria as DeadMachineInstructionElim.
+ bool SawStore = false;
+ if (!MI->isSafeToMove(&TII, 0, SawStore)) {
+ DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
+ return;
+ }
- DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
+ DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
- // Collect virtual registers to be erased after MI is gone.
- SmallVector<unsigned, 8> RegsToErase;
- bool ReadsPhysRegs = false;
-
- // 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)) {
- // Check if MI reads any unreserved physregs.
- if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
- ReadsPhysRegs = true;
- continue;
- }
- LiveInterval &LI = LIS.getInterval(Reg);
-
- // Shrink read registers, unless it is likely to be expensive and
- // unlikely to change anything. We typically don't want to shrink the
- // PIC base register that has lots of uses everywhere.
- // Always shrink COPY uses that probably come from live range splitting.
- if (MI->readsVirtualRegister(Reg) &&
- (MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
- LI.killedAt(Idx)))
- ToShrink.insert(&LI);
-
- // Remove defined value.
- if (MOI->isDef()) {
- if (VNInfo *VNI = LI.getVNInfoAt(Idx)) {
- if (TheDelegate)
- TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
- LI.removeValNo(VNI);
- if (LI.empty())
- RegsToErase.push_back(Reg);
- }
- }
- }
+ // Collect virtual registers to be erased after MI is gone.
+ SmallVector<unsigned, 8> RegsToErase;
+ bool ReadsPhysRegs = false;
+
+ // 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)) {
+ // Check if MI reads any unreserved physregs.
+ if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
+ ReadsPhysRegs = true;
+ continue;
+ }
+ LiveInterval &LI = LIS.getInterval(Reg);
- // Currently, we don't support DCE of physreg live ranges. If MI reads
- // any unreserved physregs, don't erase the instruction, but turn it into
- // a KILL instead. This way, the physreg live ranges don't end up
- // dangling.
- // FIXME: It would be better to have something like shrinkToUses() for
- // physregs. That could potentially enable more DCE and it would free up
- // the physreg. It would not happen often, though.
- if (ReadsPhysRegs) {
- MI->setDesc(TII.get(TargetOpcode::KILL));
- // Remove all operands that aren't physregs.
- for (unsigned i = MI->getNumOperands(); i; --i) {
- const MachineOperand &MO = MI->getOperand(i-1);
- if (MO.isReg() && TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
- continue;
- MI->RemoveOperand(i-1);
- }
- DEBUG(dbgs() << "Converted physregs to:\t" << *MI);
- } else {
+ // Shrink read registers, unless it is likely to be expensive and
+ // unlikely to change anything. We typically don't want to shrink the
+ // PIC base register that has lots of uses everywhere.
+ // Always shrink COPY uses that probably come from live range splitting.
+ if (MI->readsVirtualRegister(Reg) &&
+ (MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
+ LI.killedAt(Idx)))
+ ToShrink.insert(&LI);
+
+ // Remove defined value.
+ if (MOI->isDef()) {
+ if (VNInfo *VNI = LI.getVNInfoAt(Idx)) {
if (TheDelegate)
- TheDelegate->LRE_WillEraseInstruction(MI);
- LIS.RemoveMachineInstrFromMaps(MI);
- MI->eraseFromParent();
- ++NumDCEDeleted;
+ TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
+ LI.removeValNo(VNI);
+ if (LI.empty())
+ RegsToErase.push_back(Reg);
}
+ }
+ }
- // Erase any virtregs that are now empty and unused. There may be <undef>
- // uses around. Keep the empty live range in that case.
- for (unsigned i = 0, e = RegsToErase.size(); i != e; ++i) {
- unsigned Reg = RegsToErase[i];
- if (LIS.hasInterval(Reg) && MRI.reg_nodbg_empty(Reg)) {
- ToShrink.remove(&LIS.getInterval(Reg));
- eraseVirtReg(Reg);
- }
- }
+ // Currently, we don't support DCE of physreg live ranges. If MI reads
+ // any unreserved physregs, don't erase the instruction, but turn it into
+ // a KILL instead. This way, the physreg live ranges don't end up
+ // dangling.
+ // FIXME: It would be better to have something like shrinkToUses() for
+ // physregs. That could potentially enable more DCE and it would free up
+ // the physreg. It would not happen often, though.
+ if (ReadsPhysRegs) {
+ MI->setDesc(TII.get(TargetOpcode::KILL));
+ // Remove all operands that aren't physregs.
+ for (unsigned i = MI->getNumOperands(); i; --i) {
+ const MachineOperand &MO = MI->getOperand(i-1);
+ if (MO.isReg() && TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
+ continue;
+ MI->RemoveOperand(i-1);
}
+ DEBUG(dbgs() << "Converted physregs to:\t" << *MI);
+ } else {
+ if (TheDelegate)
+ TheDelegate->LRE_WillEraseInstruction(MI);
+ LIS.RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+ ++NumDCEDeleted;
+ }
+
+ // Erase any virtregs that are now empty and unused. There may be <undef>
+ // uses around. Keep the empty live range in that case.
+ for (unsigned i = 0, e = RegsToErase.size(); i != e; ++i) {
+ unsigned Reg = RegsToErase[i];
+ if (LIS.hasInterval(Reg) && MRI.reg_nodbg_empty(Reg)) {
+ ToShrink.remove(&LIS.getInterval(Reg));
+ eraseVirtReg(Reg);
+ }
+ }
+}
+
+void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
+ ArrayRef<unsigned> RegsBeingSpilled) {
+ ToShrinkSet ToShrink;
+
+ for (;;) {
+ // Erase all dead defs.
+ while (!Dead.empty())
+ eliminateDeadDef(Dead.pop_back_val(), ToShrink);
if (ToShrink.empty())
break;
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