[AMDGPU] Return better Changed status from SILowerControlFlow

[piotr]

llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp

913

It looks optimizeEndCf may also make some changes, but you detect this already earlier in the swtich statement (when checking for the presence of SI_END_CF), so it does not require any further changes, right?

[foad]

llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp

913

Right, it won't do anything unless there was an SI_END_CF instruction in the function, which was detected earlier.

[piotr]

LGTM

llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp

if (CanDemote && !IsKillBlock) {
         if (MI.getOpcode() == AMDGPU::SI_DEMOTE_I1) {
           KillBlocks.insert(&MBB);
           break;
         }
       }
     }
   }
 
+  bool Changed = false;
   MachineFunction::iterator NextBB;
   for (MachineFunction::iterator BI = MF.begin();
        BI != MF.end(); BI = NextBB) {
     NextBB = std::next(BI);
     MachineBasicBlock *MBB = &*BI;
 
     MachineBasicBlock::iterator I, E, Next;
     E = MBB->end();
     for (I = MBB->begin(); I != E; I = Next) {
       Next = std::next(I);
       MachineInstr &MI = *I;
       MachineBasicBlock *SplitMBB = MBB;
 
       switch (MI.getOpcode()) {
       case AMDGPU::SI_IF:
       case AMDGPU::SI_ELSE:
       case AMDGPU::SI_IF_BREAK:
       case AMDGPU::SI_WATERFALL_LOOP:
       case AMDGPU::SI_LOOP:
       case AMDGPU::SI_END_CF:
         SplitMBB = process(MI);
+        Changed = true;
         break;
 
       // FIXME: find a better place for this
       case AMDGPU::SI_INIT_EXEC:
       case AMDGPU::SI_INIT_EXEC_FROM_INPUT:
         lowerInitExec(MBB, MI);
         if (LIS)
           LIS->removeAllRegUnitsForPhysReg(AMDGPU::EXEC);
+        Changed = true;
         break;
 
       default:
         break;
       }
 
       if (SplitMBB != MBB) {
         MBB = Next->getParent();
         E = MBB->end();
       }
     }
   }
 
   optimizeEndCf();
 
   LoweredEndCf.clear();
   LoweredIf.clear();
   KillBlocks.clear();
 
-  return true;
+  return Changed;
 }