Add optimization bisect opt-in calls for SystemZ passes

[andrew.w.kaylor]

Summary

This patch adds calls to SystemZ-specific passes that can be safely skipped to opt-in to the optimization bisect mechanism.

I selected the passes to be skipped based on the fact that they were not added at CodeGenOpt::None in SystemZTargetMachine.cpp. Based on that criteria, I did not add opt-in calls to the SystemZLongBranch pass, which appear to be required.

Note that the call to skipFunction() will also check for the "optnone" function attribute, so this can theoretically result in passes being skipped even when optimization bisect is not being done. However, I believe that any pass that can be safely skipped should be skipped for functions with the optnone attribute.

See D19172 for details on the base optimizaton bisect implementation.

[uweigand]

LGTM.

llvm/trunk/lib/Target/SystemZ/SystemZElimCompare.cpp

while (MBBI != MBB.begin()) {
     }
     if (MI->readsRegister(SystemZ::CC) && CompleteCCUsers)
       CCUsers.push_back(MI);
   }
   return Changed;
 }
 
 bool SystemZElimCompare::runOnMachineFunction(MachineFunction &F) {
+  if (skipFunction(*F.getFunction()))
+    return false;
+
   TII = static_cast<const SystemZInstrInfo *>(F.getSubtarget().getInstrInfo());
   TRI = &TII->getRegisterInfo();
 
   bool Changed = false;
   for (auto &MBB : F)
     Changed |= processBlock(MBB);
 
   return Changed;
 }

llvm/trunk/lib/Target/SystemZ/SystemZLDCleanup.cpp

 
 void SystemZLDCleanup::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
   AU.addRequired<MachineDominatorTree>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 bool SystemZLDCleanup::runOnMachineFunction(MachineFunction &F) {
+  if (skipFunction(*F.getFunction()))
+    return false;
+
   TII = static_cast<const SystemZInstrInfo *>(F.getSubtarget().getInstrInfo());
   MF = &F;
 
   SystemZMachineFunctionInfo* MFI = F.getInfo<SystemZMachineFunctionInfo>();
   if (MFI->getNumLocalDynamicTLSAccesses() < 2) {
     // No point folding accesses if there isn't at least two.
     return false;
   }

llvm/trunk/lib/Target/SystemZ/SystemZShortenInst.cpp

for (auto MBBI = MBB.rbegin(), MBBE = MBB.rend(); MBBI != MBBE; ++MBBI) {
 
     LiveRegs.stepBackward(MI);
   }
 
   return Changed;
 }
 
 bool SystemZShortenInst::runOnMachineFunction(MachineFunction &F) {
+  if (skipFunction(*F.getFunction()))
+    return false;
+
   const SystemZSubtarget &ST = F.getSubtarget<SystemZSubtarget>();
   TII = ST.getInstrInfo();
   TRI = ST.getRegisterInfo();
   LiveRegs.init(TRI);
 
   bool Changed = false;
   for (auto &MBB : F)
     Changed |= processBlock(MBB);
 
   return Changed;
 }