[AMDGPU] Mark waterfall loops as SI_WATERFALL_LOOP

[sebastian-ne]

Summary

This way, they can be detected later, e.g. by the
SIOptimizeVGPRLiveRange pass.

[foad]

llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp

425

Can you use MachineInstr::setDesc to mutate MI into an S_CBRANCH_EXECNZ, instead of creating a new instruction and erasing the old one?

llvm/lib/Target/AMDGPU/SILowerI1Copies.cpp

174 ↗

(On Diff #356637)

Is this a change in behaviour? Previously we used an S_CBRANCH_EXECNZ which would not set Divergent here.

[sebastian-ne]

Thanks for the review. I didn’t intend to change the behavior.

[foad]

Looks OK to me assuming D105192 gets approved.

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

emitLoadSRsrcFromVGPRLoop(const SIInstrInfo &TII, MachineRegisterInfo &MRI,
   // The original instruction is here; we insert the terminators after it.
   I = LoopBB.end();
 
   // Update EXEC, switch all done bits to 0 and all todo bits to 1.
   BuildMI(LoopBB, I, DL, TII.get(XorTermOpc), Exec)
       .addReg(Exec)
       .addReg(SaveExec);
 
-  BuildMI(LoopBB, I, DL, TII.get(AMDGPU::S_CBRANCH_EXECNZ)).addMBB(&LoopBB);
+  BuildMI(LoopBB, I, DL, TII.get(AMDGPU::SI_WATERFALL_LOOP)).addMBB(&LoopBB);
 }
 
 // Build a waterfall loop around \p MI, replacing the VGPR \p Rsrc register
 // with SGPRs by iterating over all unique values across all lanes.
 // Returns the loop basic block that now contains \p MI.
 static MachineBasicBlock *
 loadSRsrcFromVGPR(const SIInstrInfo &TII, MachineInstr &MI,
                   MachineOperand &Rsrc, MachineDominatorTree *MDT,

llvm/lib/Target/AMDGPU/SIInstructions.td

 
 def SI_ELSE : CFPseudoInstSI <
   (outs SReg_1:$dst),
   (ins SReg_1:$src, brtarget:$target), [], 1, 1> {
   let Size = 12;
   let hasSideEffects = 1;
 }
 
+def SI_WATERFALL_LOOP : CFPseudoInstSI <
+  (outs),
+  (ins brtarget:$target), [], 1> {
+  let Size = 8;
+  let isBranch = 1;
+  let Defs = [];
+}
+
 def SI_LOOP : CFPseudoInstSI <
   (outs), (ins SReg_1:$saved, brtarget:$target),
   [(AMDGPUloop i1:$saved, bb:$target)], 1, 1> {
   let Size = 8;
   let isBranch = 1;
   let hasSideEffects = 1;
 }
 

llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp

void SILowerControlFlow::emitLoop(MachineInstr &MI) {
 
   MI.eraseFromParent();
 }
 
 MachineBasicBlock::iterator
 SILowerControlFlow::skipIgnoreExecInstsTrivialSucc(
   MachineBasicBlock &MBB, MachineBasicBlock::iterator It) const {
 
   SmallSet<const MachineBasicBlock *, 4> Visited;
   MachineBasicBlock *B = &MBB;
   do {
     if (!Visited.insert(B).second)
       return MBB.end();
 
     auto E = B->end();
     for ( ; It != E; ++It) {
       if (TII->mayReadEXEC(*MRI, *It))
MachineBasicBlock *SILowerControlFlow::process(MachineInstr &MI) {
   case AMDGPU::SI_IF_BREAK:
     emitIfBreak(MI);
     break;
 
   case AMDGPU::SI_LOOP:
     emitLoop(MI);
     break;
 
+  case AMDGPU::SI_WATERFALL_LOOP:
+    MI.setDesc(TII->get(AMDGPU::S_CBRANCH_EXECNZ));
+    break;
+
   case AMDGPU::SI_END_CF:
     SplitBB = emitEndCf(MI);
     break;
 
   default:
     assert(false && "Attempt to process unsupported instruction");
     break;
   }
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);
         break;
 
       // FIXME: find a better place for this
       case AMDGPU::SI_INIT_EXEC:
       case AMDGPU::SI_INIT_EXEC_FROM_INPUT:

llvm/test/CodeGen/AMDGPU/mubuf-legalize-operands.mir

 # W64: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W64: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W64: [[CMP1:%[0-9]+]]:sreg_64_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W64: [[CMP:%[0-9]+]]:sreg_64_xexec = S_AND_B64 [[CMP0]], [[CMP1]], implicit-def $scc
 # W64: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W64: [[TMPEXEC:%[0-9]+]]:sreg_64_xexec = S_AND_SAVEEXEC_B64 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W64: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_IDXEN %4, killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # W64: $exec = S_XOR_B64_term $exec, [[TMPEXEC]], implicit-def $scc
-# W64: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W64: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W64-LABEL:  bb.2:
 # W64: $exec = S_MOV_B64 [[SAVEEXEC]]
 
 # W32-LABEL: name: idxen
 # W32-LABEL:  bb.0:
 # W32-NEXT: successors: %bb.1({{.*}})
 # W32: [[VRSRC:%[0-9]+]]:vreg_128 = REG_SEQUENCE %0, %subreg.sub0, %1, %subreg.sub1, %2, %subreg.sub2, %3, %subreg.sub3
 # W32: [[SAVEEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_MOV_B32 $exec_lo
 # W32-LABEL: bb.1:
 # W32-NEXT: successors: %bb.1({{.*}}), %bb.2({{.*}})
 # W32: [[SRSRC0:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub0, implicit $exec
 # W32: [[SRSRC1:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub1, implicit $exec
 # W32: [[STMP0:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1
 # W32: [[CMP0:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP0]], [[VRSRC]].sub0_sub1, implicit $exec
 # W32: [[SRSRC2:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub2, implicit $exec
 # W32: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W32: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W32: [[CMP1:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W32: [[CMP:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_B32 [[CMP0]], [[CMP1]], implicit-def $scc
 # W32: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W32: [[TMPEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_SAVEEXEC_B32 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W32: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_IDXEN %4, killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # TODO: S_XOR_B32_term should be `implicit-def $scc`
 # W32: $exec_lo = S_XOR_B32_term $exec_lo, [[TMPEXEC]]
-# W32: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W32: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W32-LABEL:  bb.2:
 # W32: $exec_lo = S_MOV_B32 [[SAVEEXEC]]
 ---
 name:            idxen
 liveins:
   - { reg: '$vgpr0', virtual-reg: '%0' }
   - { reg: '$vgpr1', virtual-reg: '%1' }
   - { reg: '$vgpr2', virtual-reg: '%2' }

 # W64: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W64: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W64: [[CMP1:%[0-9]+]]:sreg_64_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W64: [[CMP:%[0-9]+]]:sreg_64_xexec = S_AND_B64 [[CMP0]], [[CMP1]], implicit-def $scc
 # W64: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W64: [[TMPEXEC:%[0-9]+]]:sreg_64_xexec = S_AND_SAVEEXEC_B64 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W64: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_OFFEN %4, killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # W64: $exec = S_XOR_B64_term $exec, [[TMPEXEC]], implicit-def $scc
-# W64: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W64: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W64-LABEL:  bb.2:
 # W64: $exec = S_MOV_B64 [[SAVEEXEC]]
 
 # W32-LABEL: name: offen
 # W32-LABEL:  bb.0:
 # W32-NEXT: successors: %bb.1({{.*}})
 # W32: [[VRSRC:%[0-9]+]]:vreg_128 = REG_SEQUENCE %0, %subreg.sub0, %1, %subreg.sub1, %2, %subreg.sub2, %3, %subreg.sub3
 # W32: [[SAVEEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_MOV_B32 $exec_lo
 # W32-LABEL: bb.1:
 # W32-NEXT: successors: %bb.1({{.*}}), %bb.2({{.*}})
 # W32: [[SRSRC0:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub0, implicit $exec
 # W32: [[SRSRC1:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub1, implicit $exec
 # W32: [[STMP0:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1
 # W32: [[CMP0:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP0]], [[VRSRC]].sub0_sub1, implicit $exec
 # W32: [[SRSRC2:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub2, implicit $exec
 # W32: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W32: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W32: [[CMP1:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W32: [[CMP:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_B32 [[CMP0]], [[CMP1]], implicit-def $scc
 # W32: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W32: [[TMPEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_SAVEEXEC_B32 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W32: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_OFFEN %4, killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # TODO: S_XOR_B32_term should be `implicit-def $scc`
 # W32: $exec_lo = S_XOR_B32_term $exec_lo, [[TMPEXEC]]
-# W32: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W32: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W32-LABEL:  bb.2:
 # W32: $exec_lo = S_MOV_B32 [[SAVEEXEC]]
 ---
 name:            offen
 liveins:
   - { reg: '$vgpr0', virtual-reg: '%0' }
   - { reg: '$vgpr1', virtual-reg: '%1' }
   - { reg: '$vgpr2', virtual-reg: '%2' }

 # W64: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W64: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W64: [[CMP1:%[0-9]+]]:sreg_64_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W64: [[CMP:%[0-9]+]]:sreg_64_xexec = S_AND_B64 [[CMP0]], [[CMP1]], implicit-def $scc
 # W64: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W64: [[TMPEXEC:%[0-9]+]]:sreg_64_xexec = S_AND_SAVEEXEC_B64 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W64: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_BOTHEN %4, killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # W64: $exec = S_XOR_B64_term $exec, [[TMPEXEC]], implicit-def $scc
-# W64: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W64: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W64-LABEL:  bb.2:
 # W64: $exec = S_MOV_B64 [[SAVEEXEC]]
 
 # W32-LABEL: name: bothen
 # W32-LABEL:  bb.0:
 # W32-NEXT: successors: %bb.1({{.*}})
 # W32: [[VRSRC:%[0-9]+]]:vreg_128 = REG_SEQUENCE %0, %subreg.sub0, %1, %subreg.sub1, %2, %subreg.sub2, %3, %subreg.sub3
 # W32: [[SAVEEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_MOV_B32 $exec_lo
 # W32-LABEL: bb.1:
 # W32-NEXT: successors: %bb.1({{.*}}), %bb.2({{.*}})
 # W32: [[SRSRC0:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub0, implicit $exec
 # W32: [[SRSRC1:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub1, implicit $exec
 # W32: [[STMP0:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1
 # W32: [[CMP0:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP0]], [[VRSRC]].sub0_sub1, implicit $exec
 # W32: [[SRSRC2:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub2, implicit $exec
 # W32: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W32: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W32: [[CMP1:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W32: [[CMP:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_B32 [[CMP0]], [[CMP1]], implicit-def $scc
 # W32: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W32: [[TMPEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_SAVEEXEC_B32 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W32: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_BOTHEN %4, killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # TODO: S_XOR_B32_term should be `implicit-def $scc`
 # W32: $exec_lo = S_XOR_B32_term $exec_lo, [[TMPEXEC]]
-# W32: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W32: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W32-LABEL:  bb.2:
 # W32: $exec_lo = S_MOV_B32 [[SAVEEXEC]]
 ---
 name:            bothen
 liveins:
   - { reg: '$vgpr0', virtual-reg: '%0' }
   - { reg: '$vgpr1', virtual-reg: '%1' }
   - { reg: '$vgpr2', virtual-reg: '%2' }

 # W64-NO-ADDR64: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W64-NO-ADDR64: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W64-NO-ADDR64: [[CMP1:%[0-9]+]]:sreg_64_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W64-NO-ADDR64: [[CMP:%[0-9]+]]:sreg_64_xexec = S_AND_B64 [[CMP0]], [[CMP1]], implicit-def $scc
 # W64-NO-ADDR64: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W64-NO-ADDR64: [[TMPEXEC:%[0-9]+]]:sreg_64_xexec = S_AND_SAVEEXEC_B64 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W64-NO-ADDR64: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_OFFSET killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # W64-NO-ADDR64: $exec = S_XOR_B64_term $exec, [[TMPEXEC]], implicit-def $scc
-# W64-NO-ADDR64: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W64-NO-ADDR64: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W64-NO-ADDR64-LABEL:  bb.2:
 # W64-NO-ADDR64: $exec = S_MOV_B64 [[SAVEEXEC]]
 
 # W32: successors: %bb.1({{.*}})
 # W32: [[VRSRC:%[0-9]+]]:vreg_128 = REG_SEQUENCE %0, %subreg.sub0, %1, %subreg.sub1, %2, %subreg.sub2, %3, %subreg.sub3
 # W32: [[SAVEEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_MOV_B32 $exec_lo
 # W32-LABEL: bb.1:
 # W32-NEXT: successors: %bb.1({{.*}}), %bb.2({{.*}})
 # W32: [[SRSRC0:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub0, implicit $exec
 # W32: [[SRSRC1:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub1, implicit $exec
 # W32: [[STMP0:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1
 # W32: [[CMP0:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP0]], [[VRSRC]].sub0_sub1, implicit $exec
 # W32: [[SRSRC2:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub2, implicit $exec
 # W32: [[SRSRC3:%[0-9]+]]:sgpr_32 = V_READFIRSTLANE_B32 [[VRSRC]].sub3, implicit $exec
 # W32: [[STMP1:%[0-9]+]]:sgpr_64 = REG_SEQUENCE [[SRSRC2]], %subreg.sub0, [[SRSRC3]], %subreg.sub1
 # W32: [[CMP1:%[0-9]+]]:sreg_32_xm0_xexec = V_CMP_EQ_U64_e64 [[STMP1]], [[VRSRC]].sub2_sub3, implicit $exec
 # W32: [[CMP:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_B32 [[CMP0]], [[CMP1]], implicit-def $scc
 # W32: [[SRSRC:%[0-9]+]]:sgpr_128 = REG_SEQUENCE [[SRSRC0]], %subreg.sub0, [[SRSRC1]], %subreg.sub1, [[SRSRC2]], %subreg.sub2, [[SRSRC3]], %subreg.sub3
 # W32: [[TMPEXEC:%[0-9]+]]:sreg_32_xm0_xexec = S_AND_SAVEEXEC_B32 killed [[CMP]], implicit-def $exec, implicit-def $scc, implicit $exec
 # W32: {{[0-9]+}}:vgpr_32 = BUFFER_LOAD_FORMAT_X_OFFSET killed [[SRSRC]], 0, 0, 0, 0, 0, implicit $exec
 # TODO: S_XOR_B32_term should be `implicit-def $scc`
 # W32: $exec_lo = S_XOR_B32_term $exec_lo, [[TMPEXEC]]
-# W32: S_CBRANCH_EXECNZ %bb.1, implicit $exec
+# W32: SI_WATERFALL_LOOP %bb.1, implicit $exec
 # W32-LABEL:  bb.2:
 # W32: $exec_lo = S_MOV_B32 [[SAVEEXEC]]
 
 # ADDR64: [[VRSRC:%[0-9]+]]:vreg_128 = REG_SEQUENCE %0, %subreg.sub0, %1, %subreg.sub1, %2, %subreg.sub2, %3, %subreg.sub3
 # ADDR64: [[RSRCPTR:%[0-9]+]]:vreg_64 = COPY [[VRSRC]].sub0_sub1
 # ADDR64: [[ZERO64:%[0-9]+]]:sreg_64 = S_MOV_B64 0
 # ADDR64: [[RSRCFMTLO:%[0-9]+]]:sgpr_32 = S_MOV_B32 0
 # ADDR64: [[RSRCFMTHI:%[0-9]+]]:sgpr_32 = S_MOV_B32 61440