[PowerPC] Fixed missing change flag of emitRLDICWhenLoweringJumpTables

[lkail]

Summary

PPCMIPeephole::emitRLDICWhenLoweringJumpTables should return a bool value to indicate optimization is conducted or not.

[steven.zhang]

llvm/lib/Target/PowerPC/PPCMIPeephole.cpp

764

It would be more safe to have it as "Simplified |= xxxx".

[steven.zhang]

LGTM, with one minor comments. Maybe, you could commit a NFC patch to use "|=" instead of "=" to set the Simplified flag.

[lkail]

Thanks @steven.zhang, I think using = rather than |= in line 764 might cause error. I have fixed it in https://reviews.llvm.org/D63806. Other updates of Simplified are all Simplified = true, no need to replace = with |=.

llvm/lib/Target/PowerPC/PPCMIPeephole.cpp

private:
   void initialize(MachineFunction &MFParm);
 
   // Perform peepholes.
   bool simplifyCode(void);
 
   // Perform peepholes.
   bool eliminateRedundantCompare(void);
   bool eliminateRedundantTOCSaves(std::map<MachineInstr *, bool> &TOCSaves);
-  void emitRLDICWhenLoweringJumpTables(MachineInstr &MI);
+  bool emitRLDICWhenLoweringJumpTables(MachineInstr &MI);
   void UpdateTOCSaves(std::map<MachineInstr *, bool> &TOCSaves,
                       MachineInstr *MI);
 
 public:
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<MachineDominatorTree>();
     AU.addPreserved<MachineDominatorTree>();
for (MachineInstr &MI : MBB) {
                 MI.getOperand(0).getReg())
             .add(Op1);
         ToErase = &MI;
         Simplified = true;
         NumOptADDLIs++;
         break;
       }
       case PPC::RLDICR: {
-        emitRLDICWhenLoweringJumpTables(MI);
+        Simplified = emitRLDICWhenLoweringJumpTables(MI);
         break;
       }
       }
     }
 
     // If the last instruction was marked for elimination,
     // remove it now.
     if (ToErase) {
bool PPCMIPeephole::eliminateRedundantCompare(void) {
   }
 
   return Simplified;
 }
 
 // We miss the opportunity to emit an RLDIC when lowering jump tables
 // since ISEL sees only a single basic block. When selecting, the clear
 // and shift left will be in different blocks.
-void PPCMIPeephole::emitRLDICWhenLoweringJumpTables(MachineInstr &MI) {
+bool PPCMIPeephole::emitRLDICWhenLoweringJumpTables(MachineInstr &MI) {
   if (MI.getOpcode() != PPC::RLDICR)
-    return;
+    return false;
 
   unsigned SrcReg = MI.getOperand(1).getReg();
   if (!TargetRegisterInfo::isVirtualRegister(SrcReg))
-    return;
+    return false;
 
   MachineInstr *SrcMI = MRI->getVRegDef(SrcReg);
   if (SrcMI->getOpcode() != PPC::RLDICL)
-    return;
+    return false;
 
   MachineOperand MOpSHSrc = SrcMI->getOperand(2);
   MachineOperand MOpMBSrc = SrcMI->getOperand(3);
   MachineOperand MOpSHMI = MI.getOperand(2);
   MachineOperand MOpMEMI = MI.getOperand(3);
   if (!(MOpSHSrc.isImm() && MOpMBSrc.isImm() && MOpSHMI.isImm() &&
         MOpMEMI.isImm()))
-    return;
+    return false;
 
   uint64_t SHSrc = MOpSHSrc.getImm();
   uint64_t MBSrc = MOpMBSrc.getImm();
   uint64_t SHMI = MOpSHMI.getImm();
   uint64_t MEMI = MOpMEMI.getImm();
   uint64_t NewSH = SHSrc + SHMI;
   uint64_t NewMB = MBSrc - SHMI;
   if (NewMB > 63 || NewSH > 63)
-    return;
+    return false;
 
   // The bits cleared with RLDICL are [0, MBSrc).
   // The bits cleared with RLDICR are (MEMI, 63].
   // After the sequence, the bits cleared are:
   // [0, MBSrc-SHMI) and (MEMI, 63).
   //
   // The bits cleared with RLDIC are [0, NewMB) and (63-NewSH, 63].
   if ((63 - NewSH) != MEMI)
-    return;
+    return false;
 
   LLVM_DEBUG(dbgs() << "Converting pair: ");
   LLVM_DEBUG(SrcMI->dump());
   LLVM_DEBUG(MI.dump());
 
   MI.setDesc(TII->get(PPC::RLDIC));
   MI.getOperand(1).setReg(SrcMI->getOperand(1).getReg());
   MI.getOperand(2).setImm(NewSH);
   MI.getOperand(3).setImm(NewMB);
 
   LLVM_DEBUG(dbgs() << "To: ");
   LLVM_DEBUG(MI.dump());
   NumRotatesCollapsed++;
+  return true;
 }
 
 } // end default namespace
 
 INITIALIZE_PASS_BEGIN(PPCMIPeephole, DEBUG_TYPE,
                       "PowerPC MI Peephole Optimization", false, false)
 INITIALIZE_PASS_END(PPCMIPeephole, DEBUG_TYPE,
                     "PowerPC MI Peephole Optimization", false, false)
 
 char PPCMIPeephole::ID = 0;
 FunctionPass*
 llvm::createPPCMIPeepholePass() { return new PPCMIPeephole(); }