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package firrtl
package transforms
import firrtl.ir._
import firrtl.Mappers._
import firrtl.options.{Dependency, PreservesAll}
import firrtl.Utils.{isCast, NodeMap}
object InlineCastsTransform {
// Checks if an Expression is made up of only casts terminated by a Literal or Reference
// There must be at least one cast
// Note that this can have false negatives but MUST NOT have false positives
private def isSimpleCast(castSeen: Boolean)(expr: Expression): Boolean = expr match {
case _: WRef | _: Literal | _: WSubField => castSeen
case DoPrim(op, args, _,_) if isCast(op) => args.forall(isSimpleCast(true))
case _ => false
}
/** Recursively replace [[WRef]]s with new [[Expression]]s
*
* @param replace a '''mutable''' HashMap mapping [[WRef]]s to values with which the [[WRef]]
* will be replaced. It is '''not''' mutated in this function
* @param expr the Expression being transformed
* @return Returns expr with [[WRef]]s replaced by values found in replace
*/
def onExpr(replace: NodeMap)(expr: Expression): Expression = {
expr.map(onExpr(replace)) match {
case e @ WRef(name, _,_,_) =>
replace.get(name)
.filter(isSimpleCast(castSeen=false))
.getOrElse(e)
case e @ DoPrim(op, Seq(WRef(name, _,_,_)), _,_) if isCast(op) =>
replace.get(name)
.map(value => e.copy(args = Seq(value)))
.getOrElse(e)
case other => other // Not a candidate
}
}
/** Inline casts in a Statement
*
* @param netlist a '''mutable''' HashMap mapping references to [[firrtl.ir.DefNode DefNode]]s to their connected
* [[firrtl.ir.Expression Expression]]s. This function '''will''' mutate it if stmt is a [[firrtl.ir.DefNode
* DefNode]] with a value that is a cast [[PrimOp]]
* @param stmt the Statement being searched for nodes and transformed
* @return Returns stmt with casts inlined
*/
def onStmt(netlist: NodeMap)(stmt: Statement): Statement =
stmt.map(onStmt(netlist)).map(onExpr(netlist)) match {
case node @ DefNode(_, name, value) =>
netlist(name) = value
node
case other => other
}
/** Replaces truncating arithmetic in a Module */
def onMod(mod: DefModule): DefModule = mod.map(onStmt(new NodeMap))
}
/** Inline nodes that are simple casts */
class InlineCastsTransform extends Transform with PreservesAll[Transform] {
def inputForm = UnknownForm
def outputForm = UnknownForm
override val prerequisites = firrtl.stage.Forms.LowFormMinimumOptimized ++
Seq( Dependency[BlackBoxSourceHelper],
Dependency[FixAddingNegativeLiterals],
Dependency[ReplaceTruncatingArithmetic],
Dependency[InlineBitExtractionsTransform],
Dependency[PropagatePresetAnnotations] )
override val optionalPrerequisites = firrtl.stage.Forms.LowFormOptimized
override val dependents = Seq.empty
def execute(state: CircuitState): CircuitState = {
val modulesx = state.circuit.modules.map(InlineCastsTransform.onMod(_))
state.copy(circuit = state.circuit.copy(modules = modulesx))
}
}
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