AMDGPU: Remove SI_DEMOTE_I1_TERMINATOR

It was misleadingly named and is redundant with SI_KILL_I1_TERMINATOR.

When executing a "demote" in code that has no subsequent WQM execution, we
can just replace that "demote" with a "kill".

Change-Id: I502c1f0ca6f290ead00fb0e85f0e9d89e866e266

Author: nhaehnle

llvm/lib/Target/AMDGPU/SIInsertSkips.cpp

@@ -309,7 +309,6 @@ bool SIInsertSkips::kill(MachineInstr &MI) {
     }
     return true;
   }
-  case AMDGPU::SI_DEMOTE_I1_TERMINATOR:
   case AMDGPU::SI_KILL_I1_TERMINATOR: {
     const MachineFunction *MF = MI.getParent()->getParent();
     const GCNSubtarget &ST = MF->getSubtarget<GCNSubtarget>();
@@ -487,8 +486,7 @@ bool SIInsertSkips::runOnMachineFunction(MachineFunction &MF) {
         break;
 
       case AMDGPU::SI_KILL_F32_COND_IMM_TERMINATOR:
-      case AMDGPU::SI_KILL_I1_TERMINATOR:
-      case AMDGPU::SI_DEMOTE_I1_TERMINATOR: {
+      case AMDGPU::SI_KILL_I1_TERMINATOR: {
         MadeChange = true;
         bool CanKill = kill(MI);
 

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

@@ -2074,7 +2074,6 @@ bool SIInstrInfo::analyzeBranch(MachineBasicBlock &MBB, MachineBasicBlock *&TBB,
     case AMDGPU::SI_ELSE:
     case AMDGPU::SI_KILL_I1_TERMINATOR:
     case AMDGPU::SI_KILL_F32_COND_IMM_TERMINATOR:
-    case AMDGPU::SI_DEMOTE_I1_TERMINATOR:
       // FIXME: It's messy that these need to be considered here at all.
       return true;
     default:
@@ -6355,7 +6354,6 @@ bool SIInstrInfo::isKillTerminator(unsigned Opcode) {
   switch (Opcode) {
   case AMDGPU::SI_KILL_F32_COND_IMM_TERMINATOR:
   case AMDGPU::SI_KILL_I1_TERMINATOR:
-  case AMDGPU::SI_DEMOTE_I1_TERMINATOR:
     return true;
   default:
     return false;

llvm/lib/Target/AMDGPU/SIInstructions.td

@@ -381,11 +381,12 @@ def SI_WQM_HELPER : PseudoInstSI <
 }
 
 let Defs = [EXEC] in {
+// Demote: Turn a pixel shader thread into a helper lane.
+// Threads may exit entirely after demote if their quad has been reduced to
+// contain only helper lanes. (TODO: implement this)
 def SI_DEMOTE_I1 : SPseudoInstSI <(outs), (ins SCSrc_i1:$src, i1imm:$killvalue)> {
 }
-def SI_DEMOTE_I1_TERMINATOR : SPseudoInstSI <(outs), (ins SCSrc_i1:$src, i1imm:$killvalue)> {
-  let isTerminator = 1;
-}
+
 } // End Defs = [EXEC]
 
 } // End Uses = [EXEC]

llvm/lib/Target/AMDGPU/SIWholeQuadMode.cpp

@@ -1034,9 +1034,8 @@ MachineBasicBlock *SIWholeQuadMode::splitBlock(MachineBasicBlock *BB,
     TermMI->setDesc(TII->get(AMDGPU::S_AND_B64_term));
     break;
   case AMDGPU::SI_DEMOTE_I1:
-    TermMI->setDesc(TII->get(AMDGPU::SI_DEMOTE_I1_TERMINATOR));
-    break;
-  case AMDGPU::SI_DEMOTE_I1_TERMINATOR:
+    // We come here for demotes in Exact mode, which we can just turn into kills.
+    TermMI->setDesc(TII->get(AMDGPU::SI_KILL_I1_TERMINATOR));
     break;
   default:
     if (BB->getFirstTerminator() == BB->end()) {