//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "codegen-dce"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Pass.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/ADT/Statistic.h"
using namespace llvm;
+STATISTIC(NumDeletes, "Number of dead instructions deleted");
+
namespace {
- class VISIBILITY_HIDDEN DeadMachineInstructionElim :
- public MachineFunctionPass {
+ class DeadMachineInstructionElim : public MachineFunctionPass {
virtual bool runOnMachineFunction(MachineFunction &MF);
const TargetRegisterInfo *TRI;
public:
static char ID; // Pass identification, replacement for typeid
- DeadMachineInstructionElim() : MachineFunctionPass(&ID) {}
+ DeadMachineInstructionElim() : MachineFunctionPass(ID) {}
private:
- bool isDead(MachineInstr *MI) const;
+ bool isDead(const MachineInstr *MI) const;
};
}
char DeadMachineInstructionElim::ID = 0;
-static RegisterPass<DeadMachineInstructionElim>
-Y("dead-mi-elimination",
- "Remove dead machine instructions");
+INITIALIZE_PASS(DeadMachineInstructionElim, "dead-mi-elimination",
+ "Remove dead machine instructions", false, false);
FunctionPass *llvm::createDeadMachineInstructionElimPass() {
return new DeadMachineInstructionElim();
}
-bool DeadMachineInstructionElim::isDead(MachineInstr *MI) const {
+bool DeadMachineInstructionElim::isDead(const MachineInstr *MI) const {
// Don't delete instructions with side effects.
bool SawStore = false;
- if (!MI->isSafeToMove(TII, SawStore))
+ if (!MI->isSafeToMove(TII, 0, SawStore) && !MI->isPHI())
return false;
// Examine each operand.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
- if (MO.isRegister() && MO.isDef()) {
+ if (MO.isReg() && MO.isDef()) {
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg) ?
- LivePhysRegs[Reg] : !MRI->use_empty(Reg)) {
- // This def has a use. Don't delete the instruction!
+ LivePhysRegs[Reg] : !MRI->use_nodbg_empty(Reg)) {
+ // This def has a non-debug use. Don't delete the instruction!
return false;
}
}
// If the instruction is dead, delete it!
if (isDead(MI)) {
+ DEBUG(dbgs() << "DeadMachineInstructionElim: DELETING: " << *MI);
+ // It is possible that some DBG_VALUE instructions refer to this
+ // instruction. Examine each def operand for such references;
+ // if found, mark the DBG_VALUE as undef (but don't delete it).
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isDef())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg))
+ continue;
+ MachineRegisterInfo::use_iterator nextI;
+ for (MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg),
+ E = MRI->use_end(); I!=E; I=nextI) {
+ nextI = llvm::next(I); // I is invalidated by the setReg
+ MachineOperand& Use = I.getOperand();
+ MachineInstr *UseMI = Use.getParent();
+ if (UseMI==MI)
+ continue;
+ assert(Use.isDebug());
+ UseMI->getOperand(0).setReg(0U);
+ }
+ }
AnyChanges = true;
MI->eraseFromParent();
+ ++NumDeletes;
MIE = MBB->rend();
// MII is now pointing to the next instruction to process,
// so don't increment it.
// Record the physreg defs.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
- if (MO.isRegister() && MO.isDef()) {
+ if (MO.isReg() && MO.isDef()) {
unsigned Reg = MO.getReg();
if (Reg != 0 && TargetRegisterInfo::isPhysicalRegister(Reg)) {
LivePhysRegs.reset(Reg);
- for (const unsigned *AliasSet = TRI->getAliasSet(Reg);
- *AliasSet; ++AliasSet)
- LivePhysRegs.reset(*AliasSet);
+ // Check the subreg set, not the alias set, because a def
+ // of a super-register may still be partially live after
+ // this def.
+ for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
+ *SubRegs; ++SubRegs)
+ LivePhysRegs.reset(*SubRegs);
}
}
}
// both defined and used in the same instruction.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
- if (MO.isRegister() && MO.isUse()) {
+ if (MO.isReg() && MO.isUse()) {
unsigned Reg = MO.getReg();
if (Reg != 0 && TargetRegisterInfo::isPhysicalRegister(Reg)) {
LivePhysRegs.set(Reg);