func checkPhi(instr *ssa.Phi, dom *analysis.DominatorTree) error {
if err := errIfNonFirstClassType(instr.Type(), instr); err != nil {
return err
}
incomingBlockMap := make(map[*ssa.Block]bool, instr.NumIncoming())
for _, pred := range dom.BlockCFG().NodeForBlock(instr.Block()).Prev() {
incomingBlockMap[pred.Block()] = false
}
for i := 0; i < instr.NumIncoming(); i++ {
val, block := instr.GetIncoming(i)
if seen, exists := incomingBlockMap[block]; !exists {
return &InstrError{
Instr: instr,
Message: "Impossible incoming block `" + block.Name() + "`",
}
} else if seen {
return &InstrError{
Instr: instr,
Message: "Duplicate incoming block `" + block.Name() + "`",
}
}
if err := errIfMismatchedTypes(instr.Type(), val.Type(), instr); err != nil {
return err
}
incomingBlockMap[block] = true
if valInstr, ok := val.(ssa.Instruction); ok {
// for an incoming value to be valid, the incoming block must be dominated by the block the value comes from
if !dom.NodeForBlock(block).DominatedBy(dom.NodeForBlock(valInstr.Block()), false) {
return &InstrError{
Instr: instr,
Message: fmt.Sprintf("Value `%s` must dominate block `%s`", val.Name(), block.Name()),
}
}
}
}
for block, seen := range incomingBlockMap {
if !seen {
return &InstrError{
Instr: instr,
Message: "Missing incoming block `" + block.Name() + "`",
}
}
}
return nil
}
