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[AMDGPU] SCC live interval must be recomputed after CF lowering #81817

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[AMDGPU] SCC live interval must be recomputed after CF lowering #81817

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11 changes: 5 additions & 6 deletions llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -292,7 +292,6 @@ void SILowerControlFlow::emitIf(MachineInstr &MI) {
LIS->InsertMachineInstrInMaps(*SetExec);
LIS->InsertMachineInstrInMaps(*NewBr);

LIS->removeAllRegUnitsForPhysReg(AMDGPU::EXEC);
MI.eraseFromParent();

// FIXME: Is there a better way of adjusting the liveness? It shouldn't be
Expand Down Expand Up @@ -362,9 +361,6 @@ void SILowerControlFlow::emitElse(MachineInstr &MI) {
RecomputeRegs.insert(SrcReg);
RecomputeRegs.insert(DstReg);
LIS->createAndComputeVirtRegInterval(SaveReg);

// Let this be recomputed.
LIS->removeAllRegUnitsForPhysReg(AMDGPU::EXEC);
}

void SILowerControlFlow::emitIfBreak(MachineInstr &MI) {
Expand Down Expand Up @@ -932,8 +928,6 @@ bool SILowerControlFlow::runOnMachineFunction(MachineFunction &MF) {
case AMDGPU::SI_INIT_EXEC:
case AMDGPU::SI_INIT_EXEC_FROM_INPUT:
lowerInitExec(MBB, MI);
if (LIS)
LIS->removeAllRegUnitsForPhysReg(AMDGPU::EXEC);
Changed = true;
break;

Expand All @@ -951,6 +945,11 @@ bool SILowerControlFlow::runOnMachineFunction(MachineFunction &MF) {
optimizeEndCf();

if (LIS) {
if (Changed) {
// These will need to be recomputed for insertions and removals.
LIS->removeAllRegUnitsForPhysReg(AMDGPU::EXEC);
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@arsenm arsenm Feb 29, 2024

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exec is reserved and has no liveness tracking, not sure why it was handled before

LIS->removeAllRegUnitsForPhysReg(AMDGPU::SCC);
}
for (Register Reg : RecomputeRegs) {
LIS->removeInterval(Reg);
LIS->createAndComputeVirtRegInterval(Reg);
Expand Down