Automerge: Revert "[AMDGPU] SIFixSgprCopies should not process twice VGPR to SGPR copies inserted by PHI preprocessing. (#134153)"

This reverts commit 0563569.

Breaks tests, see comments on llvm/llvm-project#134153

Author: nico

llvm/lib/Target/AMDGPU/SIFixSGPRCopies.cpp

@@ -127,7 +127,6 @@ class SIFixSGPRCopies {
   unsigned NextVGPRToSGPRCopyID = 0;
   MapVector<unsigned, V2SCopyInfo> V2SCopies;
   DenseMap<MachineInstr *, SetVector<unsigned>> SiblingPenalty;
-  DenseSet<MachineInstr *> PHISources;
 
 public:
   MachineRegisterInfo *MRI;
@@ -692,8 +691,10 @@ bool SIFixSGPRCopies::run(MachineFunction &MF) {
                             TII->get(AMDGPU::COPY), NewDst)
                         .addReg(MO.getReg());
                 MO.setReg(NewDst);
+
+                // FIXME: We are transitively revisiting users of this
+                // instruction for every input.
                 analyzeVGPRToSGPRCopy(NewCopy);
-                PHISources.insert(NewCopy);
               }
             }
           }
@@ -800,7 +801,6 @@ bool SIFixSGPRCopies::run(MachineFunction &MF) {
   RegSequences.clear();
   PHINodes.clear();
   S2VCopies.clear();
-  PHISources.clear();
 
   return true;
 }
@@ -926,13 +926,13 @@ bool SIFixSGPRCopies::lowerSpecialCase(MachineInstr &MI,
 }
 
 void SIFixSGPRCopies::analyzeVGPRToSGPRCopy(MachineInstr* MI) {
-  if (PHISources.contains(MI))
-    return;
   Register DstReg = MI->getOperand(0).getReg();
   const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
 
   V2SCopyInfo Info(getNextVGPRToSGPRCopyId(), MI,
                       TRI->getRegSizeInBits(*DstRC));
+  V2SCopies[Info.ID] = Info;
+
   SmallVector<MachineInstr *, 8> AnalysisWorklist;
   // Needed because the SSA is not a tree but a graph and may have
   // forks and joins. We should not then go same way twice.
@@ -971,18 +971,16 @@ void SIFixSGPRCopies::analyzeVGPRToSGPRCopy(MachineInstr* MI) {
       }
     } else if (Inst->getNumExplicitDefs() != 0) {
       Register Reg = Inst->getOperand(0).getReg();
-      if (Reg.isVirtual() && TRI->isSGPRReg(*MRI, Reg) && !TII->isVALU(*Inst)) {
+      if (TRI->isSGPRReg(*MRI, Reg) && !TII->isVALU(*Inst))
         for (auto &U : MRI->use_instructions(Reg))
           Users.push_back(&U);
-      }
     }
     for (auto *U : Users) {
       if (TII->isSALU(*U))
         Info.SChain.insert(U);
       AnalysisWorklist.push_back(U);
     }
   }
-  V2SCopies[Info.ID] = Info;
 }
 
 // The main function that computes the VGPR to SGPR copy score