//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "phi-opt"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/IR/Function.h"
#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Function.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
+#define DEBUG_TYPE "phi-opt"
+
STATISTIC(NumPHICycles, "Number of PHI cycles replaced");
+STATISTIC(NumDeadPHICycles, "Number of dead PHI cycles");
namespace {
class OptimizePHIs : public MachineFunctionPass {
public:
static char ID; // Pass identification
- OptimizePHIs() : MachineFunctionPass(&ID) {}
+ OptimizePHIs() : MachineFunctionPass(ID) {
+ initializeOptimizePHIsPass(*PassRegistry::getPassRegistry());
+ }
- virtual bool runOnMachineFunction(MachineFunction &MF);
+ bool runOnMachineFunction(MachineFunction &MF) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
- bool IsSingleValuePHICycle(const MachineInstr *MI, unsigned &SingleValReg,
- SmallSet<unsigned, 16> &RegsInCycle);
- bool ReplacePHICycles(MachineBasicBlock &MBB);
+ typedef SmallPtrSet<MachineInstr*, 16> InstrSet;
+ typedef SmallPtrSetIterator<MachineInstr*> InstrSetIterator;
+
+ bool IsSingleValuePHICycle(MachineInstr *MI, unsigned &SingleValReg,
+ InstrSet &PHIsInCycle);
+ bool IsDeadPHICycle(MachineInstr *MI, InstrSet &PHIsInCycle);
+ bool OptimizeBB(MachineBasicBlock &MBB);
};
}
char OptimizePHIs::ID = 0;
-static RegisterPass<OptimizePHIs>
-X("opt-phis", "Optimize machine instruction PHIs");
-
-FunctionPass *llvm::createOptimizePHIsPass() { return new OptimizePHIs(); }
+char &llvm::OptimizePHIsID = OptimizePHIs::ID;
+INITIALIZE_PASS(OptimizePHIs, "opt-phis",
+ "Optimize machine instruction PHIs", false, false)
bool OptimizePHIs::runOnMachineFunction(MachineFunction &Fn) {
+ if (skipOptnoneFunction(*Fn.getFunction()))
+ return false;
+
MRI = &Fn.getRegInfo();
- TII = Fn.getTarget().getInstrInfo();
+ TII = Fn.getSubtarget().getInstrInfo();
- // Find PHI cycles that can be replaced by a single value. InstCombine
- // does this, but DAG legalization may introduce new opportunities, e.g.,
- // when i64 values are split up for 32-bit targets.
+ // Find dead PHI cycles and PHI cycles that can be replaced by a single
+ // value. InstCombine does these optimizations, but DAG legalization may
+ // introduce new opportunities, e.g., when i64 values are split up for
+ // 32-bit targets.
bool Changed = false;
for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
- Changed |= ReplacePHICycles(*I);
+ Changed |= OptimizeBB(*I);
return Changed;
}
/// IsSingleValuePHICycle - Check if MI is a PHI where all the source operands
/// are copies of SingleValReg, possibly via copies through other PHIs. If
/// SingleValReg is zero on entry, it is set to the register with the single
-/// non-copy value. RegsInCycle is a set used to keep track of the PHIs that
+/// non-copy value. PHIsInCycle is a set used to keep track of the PHIs that
/// have been scanned.
-bool OptimizePHIs::IsSingleValuePHICycle(const MachineInstr *MI,
+bool OptimizePHIs::IsSingleValuePHICycle(MachineInstr *MI,
unsigned &SingleValReg,
- SmallSet<unsigned, 16> &RegsInCycle) {
+ InstrSet &PHIsInCycle) {
assert(MI->isPHI() && "IsSingleValuePHICycle expects a PHI instruction");
unsigned DstReg = MI->getOperand(0).getReg();
// See if we already saw this register.
- if (!RegsInCycle.insert(DstReg))
+ if (!PHIsInCycle.insert(MI).second)
return true;
// Don't scan crazily complex things.
- if (RegsInCycle.size() == 16)
+ if (PHIsInCycle.size() == 16)
return false;
// Scan the PHI operands.
unsigned SrcReg = MI->getOperand(i).getReg();
if (SrcReg == DstReg)
continue;
- const MachineInstr *SrcMI = MRI->getVRegDef(SrcReg);
+ MachineInstr *SrcMI = MRI->getVRegDef(SrcReg);
// Skip over register-to-register moves.
- unsigned MvSrcReg, MvDstReg, SrcSubIdx, DstSubIdx;
- if (SrcMI &&
- TII->isMoveInstr(*SrcMI, MvSrcReg, MvDstReg, SrcSubIdx, DstSubIdx) &&
- SrcSubIdx == 0 && DstSubIdx == 0 &&
- TargetRegisterInfo::isVirtualRegister(MvSrcReg))
- SrcMI = MRI->getVRegDef(MvSrcReg);
+ if (SrcMI && SrcMI->isCopy() &&
+ !SrcMI->getOperand(0).getSubReg() &&
+ !SrcMI->getOperand(1).getSubReg() &&
+ TargetRegisterInfo::isVirtualRegister(SrcMI->getOperand(1).getReg()))
+ SrcMI = MRI->getVRegDef(SrcMI->getOperand(1).getReg());
if (!SrcMI)
return false;
if (SrcMI->isPHI()) {
- if (!IsSingleValuePHICycle(SrcMI, SingleValReg, RegsInCycle))
+ if (!IsSingleValuePHICycle(SrcMI, SingleValReg, PHIsInCycle))
return false;
} else {
// Fail if there is more than one non-phi/non-move register.
return true;
}
-/// ReplacePHICycles - Find PHI cycles that can be replaced by a single
-/// value and remove them.
-bool OptimizePHIs::ReplacePHICycles(MachineBasicBlock &MBB) {
+/// IsDeadPHICycle - Check if the register defined by a PHI is only used by
+/// other PHIs in a cycle.
+bool OptimizePHIs::IsDeadPHICycle(MachineInstr *MI, InstrSet &PHIsInCycle) {
+ assert(MI->isPHI() && "IsDeadPHICycle expects a PHI instruction");
+ unsigned DstReg = MI->getOperand(0).getReg();
+ assert(TargetRegisterInfo::isVirtualRegister(DstReg) &&
+ "PHI destination is not a virtual register");
+
+ // See if we already saw this register.
+ if (!PHIsInCycle.insert(MI).second)
+ return true;
+
+ // Don't scan crazily complex things.
+ if (PHIsInCycle.size() == 16)
+ return false;
+
+ for (MachineInstr &UseMI : MRI->use_instructions(DstReg)) {
+ if (!UseMI.isPHI() || !IsDeadPHICycle(&UseMI, PHIsInCycle))
+ return false;
+ }
+
+ return true;
+}
+
+/// OptimizeBB - Remove dead PHI cycles and PHI cycles that can be replaced by
+/// a single value.
+bool OptimizePHIs::OptimizeBB(MachineBasicBlock &MBB) {
bool Changed = false;
for (MachineBasicBlock::iterator
MII = MBB.begin(), E = MBB.end(); MII != E; ) {
if (!MI->isPHI())
break;
+ // Check for single-value PHI cycles.
unsigned SingleValReg = 0;
- SmallSet<unsigned, 16> RegsInCycle;
- if (IsSingleValuePHICycle(MI, SingleValReg, RegsInCycle) &&
+ InstrSet PHIsInCycle;
+ if (IsSingleValuePHICycle(MI, SingleValReg, PHIsInCycle) &&
SingleValReg != 0) {
- MRI->replaceRegWith(MI->getOperand(0).getReg(), SingleValReg);
+ unsigned OldReg = MI->getOperand(0).getReg();
+ if (!MRI->constrainRegClass(SingleValReg, MRI->getRegClass(OldReg)))
+ continue;
+
+ MRI->replaceRegWith(OldReg, SingleValReg);
MI->eraseFromParent();
++NumPHICycles;
Changed = true;
+ continue;
+ }
+
+ // Check for dead PHI cycles.
+ PHIsInCycle.clear();
+ if (IsDeadPHICycle(MI, PHIsInCycle)) {
+ for (InstrSetIterator PI = PHIsInCycle.begin(), PE = PHIsInCycle.end();
+ PI != PE; ++PI) {
+ MachineInstr *PhiMI = *PI;
+ if (&*MII == PhiMI)
+ ++MII;
+ PhiMI->eraseFromParent();
+ }
+ ++NumDeadPHICycles;
+ Changed = true;
}
}
return Changed;
projects / oota-llvm.git / blobdiff